Measurement and marking metrology science
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Oct 15, 2024
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About This Presentation
Measurement
Slide Content
Unit II –Linear and
Angular Measurements:
Angular Measurements:
Linear Measurements:
Measuring length is fundamental to our everyday life.
Measuring length is fundamental to our everyday life.
Three tools of precision measurement for length –a
precision ruler, a vernier caliper and a micrometer –
govern length metrology and form the base for
further study of metrology.
An extension of steel rule for
measuring highly precise
values based on the divisions
in the sliding scale.
Extension of vernier scale. Uses
threaded scale rather than sliding
scale.
precision ruler, a vernier caliper and a micrometer –
govern length metrology and form the base for
further study of metrology.
An extension of steel rule for
measuring highly precise
values based on the divisions
in the sliding scale.
Extension of vernier scale. Uses
threaded scale rather than sliding
scale.
Definition of Linear Metrology:
It is defined as the science of linear measurements,
for the determination of distance between two points
in a straight line.
It is applicable to all external and internal
measurements –distance, length and height,
difference, diameter, thickness and wall thickness,
straightness, squareness, taper, axial and radial
runout, coaxialityand concentricity and mating
measurements.
It is defined as the science of linear measurements,
for the determination of distance between two points
in a straight line.
It is applicable to all external and internal
measurements –distance, length and height,
difference, diameter, thickness and wall thickness,
straightness, squareness, taper, axial and radial
runout, coaxialityand concentricity and mating
measurements.
Principle of operation of Linear measuring
Instruments:
To compare the dimensions to be measured with
standard dimensions marked on the measuring
instruments.
Instruments:
To compare the dimensions to be measured with
standard dimensions marked on the measuring
instruments.
Two Approaches:
1. Two point measuring contact member approach:
Out of two measuring contact members, one is
fixed and the other is movable.
Ex: Vernier Caliper and Micrometer
2. Three point measuring contact member approach:
Out of three contacting members, two are fixed
and remaining is movable.
Ex: To measure the diameter of a bar held in a V-Block
1. Two point measuring contact member approach:
Out of two measuring contact members, one is
fixed and the other is movable.
Ex: Vernier Caliper and Micrometer
2. Three point measuring contact member approach:
Out of three contacting members, two are fixed
and remaining is movable.
Ex: To measure the diameter of a bar held in a V-Block
Classification of Length Measuring
Instruments:
1.Non-Precision measuring Instruments. Ex: Steel
rule.
2.Precision Measuring Instruments. Ex: Vernier and
micrometer.
3.Direct Measuring Instruments. Ex: Scale.
4.Indirect Measuring Instruments. Ex: Dial Gauge.
When an Instrument is said to be Precise?
If the dimensions measured by the instrument
are less than 0.25mm, it is said to be a precision
instrument and the error produced by such an
instrument must not be more than 0.0025mmfor all
measured dimensions.
Instruments:
1.Non-Precision measuring Instruments. Ex: Steel
rule.
2.Precision Measuring Instruments. Ex: Vernier and
micrometer.
3.Direct Measuring Instruments. Ex: Scale.
4.Indirect Measuring Instruments. Ex: Dial Gauge.
When an Instrument is said to be Precise?
If the dimensions measured by the instrument
are less than 0.25mm, it is said to be a precision
instrument and the error produced by such an
instrument must not be more than 0.0025mmfor all
measured dimensions.
Important Linear Measuring Instruments:
Steel Rule
Vernier Instruments
Calipers
Micrometer
Slip gauge
Interferometry
Optical Flats
Limit Gauges
Steel Rule
Vernier Instruments
Calipers
Micrometer
Slip gauge
Interferometry
Optical Flats
Limit Gauges
Steel Rule:
Simplest and most commonly used linear instrument.
It is the part replica of the International Prototype of
meter.
They are marked with a graduated scale and whose
smallest intervals are one millimeter.
To increase its versatility, some scales are marked
with 0.5mm in between them.
They are available in lengths of 150, 300, 600 or
1000 mm.
They can be used for direct comparison with the
object to be measured.
Sometimes outside and inside calipers can be used
in conjunction with a scale.
Simplest and most commonly used linear instrument.
It is the part replica of the International Prototype of
meter.
They are marked with a graduated scale and whose
smallest intervals are one millimeter.
To increase its versatility, some scales are marked
with 0.5mm in between them.
They are available in lengths of 150, 300, 600 or
1000 mm.
They can be used for direct comparison with the
object to be measured.
Sometimes outside and inside calipers can be used
in conjunction with a scale.
They have an anodized profile with minimum
thickness and wear resistant ultraviolet curved
screen printing.
They should be made of good quality spring steel
and be chrome plated to prevent corrosion.
The main problem with the steel rule is its parallax
error.
Nowadays battery operated digital scales are used
to measure travels of machines. Ex: Drilling ,milling
machines.
Has a maximum measuring speed of 1.5m/s and is
equipped with a high contrast 6mm liquid crystal
display.
thickness and wear resistant ultraviolet curved
screen printing.
They should be made of good quality spring steel
and be chrome plated to prevent corrosion.
The main problem with the steel rule is its parallax
error.
Nowadays battery operated digital scales are used
to measure travels of machines. Ex: Drilling ,milling
machines.
Has a maximum measuring speed of 1.5m/s and is
equipped with a high contrast 6mm liquid crystal
display.
Caliper:
An end standard measuring instrument to measure
the distance between two points.
An end standard measuring instrument to measure
the distance between two points.
Calipers typically use a precise slide movement for
inside, outside, depth or step measurement.
They do not have a graduated scale or display and
are only used for comparing or transferring
dimensions as secondary measuring instruments for
indirect measurements.
Consists of two legs hinged at top with the ends of
the legs spanning the part to be measured.
Made from alloy steels.
Measuring ends are suitably hardened and
tempered.
Accuracy of measurement depends on the sense of
feel that can only be acquired by experience.
inside, outside, depth or step measurement.
They do not have a graduated scale or display and
are only used for comparing or transferring
dimensions as secondary measuring instruments for
indirect measurements.
Consists of two legs hinged at top with the ends of
the legs spanning the part to be measured.
Made from alloy steels.
Measuring ends are suitably hardened and
tempered.
Accuracy of measurement depends on the sense of
feel that can only be acquired by experience.
Types of Calipers:
Inside Calipers: Made with straight legs, which are
bend outwards at ends and are used for measuring
hole diameters, distance between shoulders. Then
the opening can be checked by a rule or micrometer.
Outside Calipers: Have two legs which are bent
inward and are used for measuring and comparing
diameters, thickness and outside dimensions by
transferring the readings to a steel rule or
micrometer or vernier caliper.
Inside and outside calipers are available in sizes of
75, 100, 150, 200, 250 and 300mm.
Inside Calipers: Made with straight legs, which are
bend outwards at ends and are used for measuring
hole diameters, distance between shoulders. Then
the opening can be checked by a rule or micrometer.
Outside Calipers: Have two legs which are bent
inward and are used for measuring and comparing
diameters, thickness and outside dimensions by
transferring the readings to a steel rule or
micrometer or vernier caliper.
Inside and outside calipers are available in sizes of
75, 100, 150, 200, 250 and 300mm.
Vernier Caliper:
A vernier caliper is a combination of inside and
outside caliper.
Has two sets of jaws.
Pierre vernier devised the principle of vernier in
1631.
A vernier caliper is a combination of inside and
outside caliper.
Has two sets of jaws.
Pierre vernier devised the principle of vernier in
1631.
Principle: The difference between two scales or
divisions which are near, but not alike are required
for obtaining a small difference.
The first instrument developed following vernier’s
principle was a sliding caliper.
It was first manufactured in 1868 and steel and brass
were used for its production.
It consists of two steel rules and these can slide
along each other.
A solid L-shaped frame is engraved with the main
scale or the true scale and has each small unit as
exactly 1 millimeter and the beam and the fixed jaw
are exactly at 90˚ to each other.
divisions which are near, but not alike are required
for obtaining a small difference.
The first instrument developed following vernier’s
principle was a sliding caliper.
It was first manufactured in 1868 and steel and brass
were used for its production.
It consists of two steel rules and these can slide
along each other.
A solid L-shaped frame is engraved with the main
scale or the true scale and has each small unit as
exactly 1 millimeter and the beam and the fixed jaw
are exactly at 90˚ to each other.
It consists of a movable jaw which is also called as
vernier scale.
The function of the vernierscale is to subdivide
minor divisions on the main scale into smallest
increments that the vernierinstrument is capable of
measuring.
Some of the verniershave fine adjustment clamp roll
for precise adjustment.
There is a locking screw to fix the movable jaw to
take correct measurement.
Measuring blades are used for measurement of
inside dimensions.
Depth bar is used to measure the depth of the
product.
Verniercaliper is polished with stain-chrome finish
for glare free reading.
vernier scale.
The function of the vernierscale is to subdivide
minor divisions on the main scale into smallest
increments that the vernierinstrument is capable of
measuring.
Some of the verniershave fine adjustment clamp roll
for precise adjustment.
There is a locking screw to fix the movable jaw to
take correct measurement.
Measuring blades are used for measurement of
inside dimensions.
Depth bar is used to measure the depth of the
product.
Verniercaliper is polished with stain-chrome finish
for glare free reading.
Verniercaliper is hardened and made of hardened
steel and they have a raised sliding surface for
protection of the scale.
There are three types of verniercalipers used to
measure various needs of external and internal
measurements upto2000mm with an accuracy of
0.02mm, 0.05mm, 0.1mm.
Various measuring ranges include 0-125, 0-200,0-
300, 0-500, 0-750, 0-1000, 750-1500, 750-2000mm.
Instructions on Use:
1.Close the jaws tightly on the object to be
measured.
2.When measuring round surfaces ensure that the
axis of the work piece is perpendicular to the
caliper.
steel and they have a raised sliding surface for
protection of the scale.
There are three types of verniercalipers used to
measure various needs of external and internal
measurements upto2000mm with an accuracy of
0.02mm, 0.05mm, 0.1mm.
Various measuring ranges include 0-125, 0-200,0-
300, 0-500, 0-750, 0-1000, 750-1500, 750-2000mm.
Instructions on Use:
1.Close the jaws tightly on the object to be
measured.
2.When measuring round surfaces ensure that the
axis of the work piece is perpendicular to the
caliper.
Least count of a verniercaliper = 1 MSD –1 VSD
1 MSD = 1mm
1VSD = (49/50)*1 MSD
1 VSD = 0.98
Therefore, LC = 1 –0.98 = 0.02mm.
Also least count can be calculated by using,
LC = Smallest division on main scale/ total no of
vernierscale divisions.
LC = 1mm/50 = 0.02mm.
Recently digital verniercalipers with LCD display ,
on/off and reset adjustment with storage of
measuring values and data transmission capabilities
are also available.
1 MSD = 1mm
1VSD = (49/50)*1 MSD
1 VSD = 0.98
Therefore, LC = 1 –0.98 = 0.02mm.
Also least count can be calculated by using,
LC = Smallest division on main scale/ total no of
vernierscale divisions.
LC = 1mm/50 = 0.02mm.
Recently digital verniercalipers with LCD display ,
on/off and reset adjustment with storage of
measuring values and data transmission capabilities
are also available.
VernierHeight Gauge:
One of the most useful and versatile instruments.
Used for measuring, inspecting and transferring the
height dimension over plane, step and curved
surfaces.
Follows the principle of verniercaliper and also
follows the same procedure for linear measurement.
Used with a wear resistant special base block in
which a graduated bar is held in the vertical
position.
Consists of a vertical graduated beam or column on
which the main scale is engraved.
Vernierscale can move up or down the beam.
Bracket carries a vernierscale and a rectangular
clamp for clamping scriber blade.
One of the most useful and versatile instruments.
Used for measuring, inspecting and transferring the
height dimension over plane, step and curved
surfaces.
Follows the principle of verniercaliper and also
follows the same procedure for linear measurement.
Used with a wear resistant special base block in
which a graduated bar is held in the vertical
position.
Consists of a vertical graduated beam or column on
which the main scale is engraved.
Vernierscale can move up or down the beam.
Bracket carries a vernierscale and a rectangular
clamp for clamping scriber blade.
Arrangement is designed such that when the tip of
the scriber blade rests on the surface plate, the zero
of the main scale coincides with the zero of the
vernierscale.
the scriber blade rests on the surface plate, the zero
of the main scale coincides with the zero of the
vernierscale.
Scriber blades can be inverted with its face pointing
upwards which enables determination of heights at
inverted faces.
Some height gauges are provided with dial gauges
which makes reading of bracket movement by dial
gauges easy and exact.
Nowadays electronic digital vernierheight gauges
are available.
They provide the advantage of immediate digital
readout of measured value, possible to store the
standard value in its memory(as a datum for further
readings and for comparing with given tolerances).
Digital presetting is also possible for entering the
reference dimensions digitally and automatically.
upwards which enables determination of heights at
inverted faces.
Some height gauges are provided with dial gauges
which makes reading of bracket movement by dial
gauges easy and exact.
Nowadays electronic digital vernierheight gauges
are available.
They provide the advantage of immediate digital
readout of measured value, possible to store the
standard value in its memory(as a datum for further
readings and for comparing with given tolerances).
Digital presetting is also possible for entering the
reference dimensions digitally and automatically.
Via a serial interface, the measured data can be
transmitted to an A4 printer or computer for
evaluation.
Fine setting is provided to facilitate the setting of the
measuring head to the desired dimensions
especially for scribing jobs enabling zero setting at
any position.
transmitted to an A4 printer or computer for
evaluation.
Fine setting is provided to facilitate the setting of the
measuring head to the desired dimensions
especially for scribing jobs enabling zero setting at
any position.
Vernier Depth Gauge:
Used to measure depth, distance from plane surface
to projection, recess, slots and steps.
The basic parts of a Vernier height gauge are base
or anvil on which the Vernier scale is calibrated
along with fine adjustment screw.
For accurate measurements, the
reference surface must be flat and free
from swarfand burrs.
•When the beam is brought in contact
with the surface being measured, the base
is held firmly against the reference surface.
Used to measure depth, distance from plane surface
to projection, recess, slots and steps.
The basic parts of a Vernier height gauge are base
or anvil on which the Vernier scale is calibrated
along with fine adjustment screw.
For accurate measurements, the
reference surface must be flat and free
from swarfand burrs.
•When the beam is brought in contact
with the surface being measured, the base
is held firmly against the reference surface.
The measuring pressure exerted should be
equivalent on the surface being measured.
The reading on this instrument follows the same
procedure as that of a Vernier caliper.
The Vernier and main scale have a stain-chrome
finish for glare-free reading with a reversible beam
and slide.
The beam is made of hardened stainless steel, while
the sliding surface is raised for protection of scale.
The battery operated digital Vernier caliper is also
available with a high contrast 6-mm liquid crystal
display having a maximum measuring speed of
1.5m/s.
equivalent on the surface being measured.
The reading on this instrument follows the same
procedure as that of a Vernier caliper.
The Vernier and main scale have a stain-chrome
finish for glare-free reading with a reversible beam
and slide.
The beam is made of hardened stainless steel, while
the sliding surface is raised for protection of scale.
The battery operated digital Vernier caliper is also
available with a high contrast 6-mm liquid crystal
display having a maximum measuring speed of
1.5m/s.
Micrometers/Screw Gauge:
MicrometershavegreateraccuracythanVerniercalipers
andareusedinmostoftheengineeringprecisionwork
involvinginterchangeabilityofcomponentparts.
Theyhaveanaccuracyof0.01mmgenerallybut
micrometerswithanaccuracyof0.001mmarealso
available.
Theyareusedtomeasurelength,width,thicknessand
diameterofajob.
MicrometershavegreateraccuracythanVerniercalipers
andareusedinmostoftheengineeringprecisionwork
involvinginterchangeabilityofcomponentparts.
Theyhaveanaccuracyof0.01mmgenerallybut
micrometerswithanaccuracyof0.001mmarealso
available.
Theyareusedtomeasurelength,width,thicknessand
diameterofajob.
Principle of Micrometer:
Itisbasedontheprincipleofscrewandnut.
Whenthescrewisturnedthroughonerevolution,thenut
advancesbyonepitchdistance.i.e.,onerotationofthe
screwcorrespondstoalinearmovementofthedistance
equaltothepitchofthethread.
Ifthecircumferenceofthescrewisdividedintonequal
parts,thenitsrotationofonedivisionwillcausethenutto
advancethroughpitch/nlength.
Theminimumlengththatcanbeusedtomeasureinsucha
casewillbepitch/nandbyincreasingthenumberof
divisionsonthecircumference,theaccuracyofthe
instrumentcanbeincreasedconsiderably.
Itisbasedontheprincipleofscrewandnut.
Whenthescrewisturnedthroughonerevolution,thenut
advancesbyonepitchdistance.i.e.,onerotationofthe
screwcorrespondstoalinearmovementofthedistance
equaltothepitchofthethread.
Ifthecircumferenceofthescrewisdividedintonequal
parts,thenitsrotationofonedivisionwillcausethenutto
advancethroughpitch/nlength.
Theminimumlengththatcanbeusedtomeasureinsucha
casewillbepitch/nandbyincreasingthenumberof
divisionsonthecircumference,theaccuracyofthe
instrumentcanbeincreasedconsiderably.
Leastcountofamicrometer=Pitch/Totalno.ofhead
scaledivisions
Pitch=Distancetravelledbythethimbleonthe
linearscaleforonerotation.
Ifthescrewhasapitchof0.5mm,thenafterevery
rotation,thespindletravelsaxiallyby0.5mm.
Andiftheconicalendofthethimbleisdividedby50
divisions,thenleastcountis
Leastcount=0.5/50=0.01mm
scaledivisions
Pitch=Distancetravelledbythethimbleonthe
linearscaleforonerotation.
Ifthescrewhasapitchof0.5mm,thenafterevery
rotation,thespindletravelsaxiallyby0.5mm.
Andiftheconicalendofthethimbleisdividedby50
divisions,thenleastcountis
Leastcount=0.5/50=0.01mm
Types of Micrometer:
It can be classified into:
1.Outside micrometer
2.Inside micrometer
3.Depth-Gauge micrometer
Components of a Micrometer:
1.U-shaped or C-shaped frame
2.Carbide-Tipped Measuring faces-Anvil and Spindle
3.Locking device
4.Barrel
5.Thimble
6.Ratchet
It can be classified into:
1.Outside micrometer
2.Inside micrometer
3.Depth-Gauge micrometer
Components of a Micrometer:
1.U-shaped or C-shaped frame
2.Carbide-Tipped Measuring faces-Anvil and Spindle
3.Locking device
4.Barrel
5.Thimble
6.Ratchet
Other types of micrometer:
1.Digital micrometer with digital display
2.Micrometer with dial comparator
3.Micrometers with sliding spindle and measuring
probes and micrometer with reduced measuring
faces
4.Micrometer with spherical anvil
5.Micrometers with sliding spindle and disc-type
anvils
6.Thread micrometers
1.Digital micrometer with digital display
2.Micrometer with dial comparator
3.Micrometers with sliding spindle and measuring
probes and micrometer with reduced measuring
faces
4.Micrometer with spherical anvil
5.Micrometers with sliding spindle and disc-type
anvils
6.Thread micrometers
Slip Gauges:
SlipGaugesarepracticalendstandardsandareusedinlinear
measurements.
InventedbytheSwedishEngineerC.E.Johnson.
Theyarerectangularblockswhicharehardenedtoresistwearandare
carefullystabilizedsothattheyareindependentofanysubsequent
variationinsizeorshape.
MadeofhighgradecaststeelorceramiccompoundZirconiumOxide
(ZrO2)havingheatexpansioncoefficientsof11.5x10^-6/Kand9.5x
10^-6/Krespectively.
Theyareavailablewitha9mmwide,30-35mmlongcrosssection.
Theyaremadeofselectgradeofcarbidewithahardnessof1500
Vickersandarecheckedforflatnessandparallelismateverystage
andcalibratedinourNABL(NationalAccreditationBoardforTesting
andCalibrationLaboratories),India.
Theyareavailableinfivegradesofaccuracy.
SlipGaugesarepracticalendstandardsandareusedinlinear
measurements.
InventedbytheSwedishEngineerC.E.Johnson.
Theyarerectangularblockswhicharehardenedtoresistwearandare
carefullystabilizedsothattheyareindependentofanysubsequent
variationinsizeorshape.
MadeofhighgradecaststeelorceramiccompoundZirconiumOxide
(ZrO2)havingheatexpansioncoefficientsof11.5x10^-6/Kand9.5x
10^-6/Krespectively.
Theyareavailablewitha9mmwide,30-35mmlongcrosssection.
Theyaremadeofselectgradeofcarbidewithahardnessof1500
Vickersandarecheckedforflatnessandparallelismateverystage
andcalibratedinourNABL(NationalAccreditationBoardforTesting
andCalibrationLaboratories),India.
Theyareavailableinfivegradesofaccuracy.
Classification of slip gauges:
i)Grade2:Itisaworkshopgradesetandusedforgeneraluse.
Usedforsettingupmachinetools,positioningmillingcutters
andcheckingmechanicalwidths.
ii)Grade1:Morecommonlyusedformorepreciseworksuch
asthatcarriedoutinagoodglasstoolroom.Usedforsetting
upsinebarsandsinetables,checkinggapgauges&settingdial
testindicatorstozero.
iii)Grade0:MorecommonlyknownasInspectionGradeand
itsuseisconfinedtotoolroomormachineshopinspection.
Theycannotbedamagedorabusedbyroughusageonshop
floors.
iv)Grade00:AlsoknownasReferenceGrade.Keptin
standardroomandwouldbekeptforworkofhighestprecision
only.Ex:DeterminationoferrorspresentinworkshoporGrade
2slips.
v)GradeK:AlsocalledasCalibrationGrade.Formeasuring
othergradesbycomparison.
i)Grade2:Itisaworkshopgradesetandusedforgeneraluse.
Usedforsettingupmachinetools,positioningmillingcutters
andcheckingmechanicalwidths.
ii)Grade1:Morecommonlyusedformorepreciseworksuch
asthatcarriedoutinagoodglasstoolroom.Usedforsetting
upsinebarsandsinetables,checkinggapgauges&settingdial
testindicatorstozero.
iii)Grade0:MorecommonlyknownasInspectionGradeand
itsuseisconfinedtotoolroomormachineshopinspection.
Theycannotbedamagedorabusedbyroughusageonshop
floors.
iv)Grade00:AlsoknownasReferenceGrade.Keptin
standardroomandwouldbekeptforworkofhighestprecision
only.Ex:DeterminationoferrorspresentinworkshoporGrade
2slips.
v)GradeK:AlsocalledasCalibrationGrade.Formeasuring
othergradesbycomparison.
Based upon accuracy, they are classified as:
Type Accuracy Accuracy of
Flatness and
Parallelism
AA-Master Slip
Gauges
±2 microns/m 75 microns
A-Reference
Gauges
±4 microns/m 125 microns
B-Working Gauges±8 microns/m 250 microns
Type Accuracy Accuracy of
Flatness and
Parallelism
AA-Master Slip
Gauges
±2 microns/m 75 microns
A-Reference
Gauges
±4 microns/m 125 microns
B-Working Gauges±8 microns/m 250 microns
AccordingtoIndianStandards,SlipGaugesareclassified
as:
Grade0–Usedforlaboratoriesandstandardroomsfor
checkingsubsequentgradegauges.
GradeI–HavingloweraccuracythanGrade0andusedin
theinspectiondepartment.
GradeII–Canbeusedintheworkshopduringactual
productionofcomponents.
Slipgaugesareavailableinvariousformslike:
Rectangular
Squarewithcenterhole
Squarewithoutcenterhole
as:
Grade0–Usedforlaboratoriesandstandardroomsfor
checkingsubsequentgradegauges.
GradeI–HavingloweraccuracythanGrade0andusedin
theinspectiondepartment.
GradeII–Canbeusedintheworkshopduringactual
productionofcomponents.
Slipgaugesareavailableinvariousformslike:
Rectangular
Squarewithcenterhole
Squarewithoutcenterhole
SalientFeatures:
1.CorrosionResistant
2.Superiorwringability
3.Resistanttoimpact
4.Resistanttowear
5.Thermalexpansion
CareandUseofSlipGauges:
1.Mustbeprotectedagainstclimaticconditionsbycovering
withahighgradepetroleumjellyorotheranti-corrosive
materials.
2.Eachgaugeistobekeptinaseparatecompartment.
3.Theymustbekeptinorder.
4.Whennotinusekeeptheminbox.
5.Mustbeusedonlyinairconditionedroomsandfreefrom
dust.
1.CorrosionResistant
2.Superiorwringability
3.Resistanttoimpact
4.Resistanttowear
5.Thermalexpansion
CareandUseofSlipGauges:
1.Mustbeprotectedagainstclimaticconditionsbycovering
withahighgradepetroleumjellyorotheranti-corrosive
materials.
2.Eachgaugeistobekeptinaseparatecompartment.
3.Theymustbekeptinorder.
4.Whennotinusekeeptheminbox.
5.Mustbeusedonlyinairconditionedroomsandfreefrom
dust.
6.Protect the gauges from getting magnetized.
7.Must be handled using a piece of chamois leather or
Perspertongs.
8.They must be wiped/cleaned every time before use.
9.They should not be placed on surface plates.
Slip Gauge Accessories:
1.Measuring Jaws –Available in two designs (for internal
and external features)
2.Scriber and center point –For marking purposes.
3.Holder and Base –To hold a combination of slip gauges.
7.Must be handled using a piece of chamois leather or
Perspertongs.
8.They must be wiped/cleaned every time before use.
9.They should not be placed on surface plates.
Slip Gauge Accessories:
1.Measuring Jaws –Available in two designs (for internal
and external features)
2.Scriber and center point –For marking purposes.
3.Holder and Base –To hold a combination of slip gauges.
Wringing of slip gauges
Angular Measurements:
Ancient ages, angular measurement was used for
setting up direction while travelling.
Sailors on high seas relied on their prismatic
compasses for finding out a desired direction.
Today precise angular measurements help in
navigation of ships and aero planes.
Also used in land surveys, in astronomy for
computing distance between stars and planets,
identifying the position of flying objects.
Ancient ages, angular measurement was used for
setting up direction while travelling.
Sailors on high seas relied on their prismatic
compasses for finding out a desired direction.
Today precise angular measurements help in
navigation of ships and aero planes.
Also used in land surveys, in astronomy for
computing distance between stars and planets,
identifying the position of flying objects.
Concept of angular measurement is important in
geometry and trigonometry.
There are two commonly used units of angular
measurement.
The more familiar one is the degree.
A circle is divided into 360 equal degrees and a
degree is further classified into minutes and
seconds.
Each degree is divided into 60 equal parts called
minutes and each minute is divided into 60 equal
parts called seconds.
Example, 2˚5’30”. In order to convert it to degrees =
2˚+
5′
60
+
30"
3600
= 2.0916˚
geometry and trigonometry.
There are two commonly used units of angular
measurement.
The more familiar one is the degree.
A circle is divided into 360 equal degrees and a
degree is further classified into minutes and
seconds.
Each degree is divided into 60 equal parts called
minutes and each minute is divided into 60 equal
parts called seconds.
Example, 2˚5’30”. In order to convert it to degrees =
2˚+
5′
60
+
30"
3600
= 2.0916˚
Other common unit of angle is radian.
The circumference of a circle is 2π, so it follows
360˚=2π.
Hence 1˚=π/180 radians and 1radian equals 180/π
degrees.
Another thing is the ratio of the arc subtended.
Hence radian measure times radius = arc length.
The circumference of a circle is 2π, so it follows
360˚=2π.
Hence 1˚=π/180 radians and 1radian equals 180/π
degrees.
Another thing is the ratio of the arc subtended.
Hence radian measure times radius = arc length.
Angle measuring Devices:
Various types of angle measuring devices include:
1.Protractors
2.Angle gauges
3.Universal Protractors
4.Combination sets
5.Protractor heads
6.Sine bars
7.T bevels
Various types of angle measuring devices include:
1.Protractors
2.Angle gauges
3.Universal Protractors
4.Combination sets
5.Protractor heads
6.Sine bars
7.T bevels
Protractors
Most common calibrated device used in drawing.
It does not perform well in establishing layouts for
work, since it requires a carefully placed and held
straight edge.
Most common calibrated device used in drawing.
It does not perform well in establishing layouts for
work, since it requires a carefully placed and held
straight edge.
Machinist’s Protractor:
Often referred to as bevel gauge.
It consists of a center finder, drill point gauge and
5,6,7,8,9 circle divider.
Often referred to as bevel gauge.
It consists of a center finder, drill point gauge and
5,6,7,8,9 circle divider.
Arm Protractor:
A very handy tool to setup and measure odd angles.
Consists of arms and a 10-minute vernier.
Almost any type of angle can be handled.
A very handy tool to setup and measure odd angles.
Consists of arms and a 10-minute vernier.
Almost any type of angle can be handled.
Angle Gauges:
Consists of a series of fixed angles for comparative
assessment of the angle between two surfaces.
Dr. Tomlinson developed angle gauges in 1941.
By making different permutations and combinations
of gauge setting, we could set an angle nearest to
3”.
Consists of a series of fixed angles for comparative
assessment of the angle between two surfaces.
Dr. Tomlinson developed angle gauges in 1941.
By making different permutations and combinations
of gauge setting, we could set an angle nearest to
3”.
Dimensions of angle gauges include 75mm length
and 16mm width.
Common materials include aluminium, brass or
bronze, cast metal or iron, plastic, fiberglass, glass,
granite, stainless steel, steel and wood.
Are hardened and stabilised.
Measuring faces are lapped and polished to a high
degree of accuracy and flatness.
Available in two different sets.
One set consists of 12 pieces with a square block.
Their values are 1˚,3˚,9˚,27˚ and 41˚, 1’,3’,9’ and 27’
and 6”, 18” and 30”.
Other set contains 13 pieces with values of 1˚, 3˚,9˚,
27˚ and 41˚, 1’, 3’, 9’ and 27’ and 3”, 6”, 18” and 30”.
and 16mm width.
Common materials include aluminium, brass or
bronze, cast metal or iron, plastic, fiberglass, glass,
granite, stainless steel, steel and wood.
Are hardened and stabilised.
Measuring faces are lapped and polished to a high
degree of accuracy and flatness.
Available in two different sets.
One set consists of 12 pieces with a square block.
Their values are 1˚,3˚,9˚,27˚ and 41˚, 1’,3’,9’ and 27’
and 6”, 18” and 30”.
Other set contains 13 pieces with values of 1˚, 3˚,9˚,
27˚ and 41˚, 1’, 3’, 9’ and 27’ and 3”, 6”, 18” and 30”.
Bevel Protractor:
Simplest instrument for measuring angle between
two faces of a component.
Consists of a base plate attached to the main body.
An adjustable blade is capable of rotating freely
about the center of the main scale engraved on the
body of the instrument and can be locked in any
position.
Simplest instrument for measuring angle between
two faces of a component.
Consists of a base plate attached to the main body.
An adjustable blade is capable of rotating freely
about the center of the main scale engraved on the
body of the instrument and can be locked in any
position.
An acute angle attachment is provided at the top for
the purpose of measuring acute angles.
Base of the base plate is made flat so that it could be
laid flat upon the work and any type of work and any
type of angle measured.
Capable of measuring from 0 to 360˚.
Consists of two scales viz. a main scale and a
vernierscale.
Vernierscale has 24 divisions coinciding with 23
main scale divisions.
Least count of the instrument is 5’.
the purpose of measuring acute angles.
Base of the base plate is made flat so that it could be
laid flat upon the work and any type of work and any
type of angle measured.
Capable of measuring from 0 to 360˚.
Consists of two scales viz. a main scale and a
vernierscale.
Vernierscale has 24 divisions coinciding with 23
main scale divisions.
Least count of the instrument is 5’.
A recent development of the instrument is the optical
bevel protractor.
It consists of a glass circle divided at 10’ interval
throughout the whole 360˚ is fitted inside the main
body.
A small microscope is fitted through which the circle
graduations can be viewed.
The adjustable blade is clamped to a rotating
member which carries this microscope.
With the aid of microscope it is possible to read by
estimation to about 2’.
Universal Bevel Protractor is also same with
accurate and precise measurements upto5’.
bevel protractor.
It consists of a glass circle divided at 10’ interval
throughout the whole 360˚ is fitted inside the main
body.
A small microscope is fitted through which the circle
graduations can be viewed.
The adjustable blade is clamped to a rotating
member which carries this microscope.
With the aid of microscope it is possible to read by
estimation to about 2’.
Universal Bevel Protractor is also same with
accurate and precise measurements upto5’.
Example:
Types of Bevel Protractors:
They are mainly classified as
1.Mechanical Bevel Protractor
2.Optical Bevel Protractor
Mechanical bevel protractors are further classified
into four types: A,B,C and D.
In type Ait is provided with all fine adjustment device
or acute angle attachment.
In type Bthere is no fine adjustment device or acute
angle attachment.
The scales of all types are graduated either as a full
circle marked 0-90-0-90 with one vernieror as
semicircle marked 0-90-0 with two verniers180˚
apart.
Type Cand Dis not provided with vernieror fine
adjustment device or acute angle attachment.
They are mainly classified as
1.Mechanical Bevel Protractor
2.Optical Bevel Protractor
Mechanical bevel protractors are further classified
into four types: A,B,C and D.
In type Ait is provided with all fine adjustment device
or acute angle attachment.
In type Bthere is no fine adjustment device or acute
angle attachment.
The scales of all types are graduated either as a full
circle marked 0-90-0-90 with one vernieror as
semicircle marked 0-90-0 with two verniers180˚
apart.
Type Cand Dis not provided with vernieror fine
adjustment device or acute angle attachment.
In optical bevel protractor, it is possible to take
readings uptoapproximately 2’of arc.
The provision is made for an internal circular scale
which is graduated in divisions of 10 minutes of arc.
Readings are taken against a fixed index line or
vernierby means of an optical magnifying system
which is internal with the instrument.
readings uptoapproximately 2’of arc.
The provision is made for an internal circular scale
which is graduated in divisions of 10 minutes of arc.
Readings are taken against a fixed index line or
vernierby means of an optical magnifying system
which is internal with the instrument.
The scale is graduated as a full circle marked 0—90—
0—90.
The zero positions correspond to the condition when the
blade is parallel to the stock.
Provision is also made for adjusting the focus of the
system to accommodate normal variations in eye-sight.
The scale and vernierare so arranged that they are
always in focus in the optical system.
General Description of Various Components:
1.Body
Itisdesignedinsuchawaythatitsbackisflatandthere
arenoprojectionsbeyonditsbacksothatwhenthebevel
protractorisplacedonitsbackonasurfaceplatethere
shallbenoperceptiblerock.Theflatnessoftheworking
edgeofthestockandbodyistestedbycheckingthe
squarenessofbladewithrespecttostockwhenbladeisset
at90°.
0—90.
The zero positions correspond to the condition when the
blade is parallel to the stock.
Provision is also made for adjusting the focus of the
system to accommodate normal variations in eye-sight.
The scale and vernierare so arranged that they are
always in focus in the optical system.
General Description of Various Components:
1.Body
Itisdesignedinsuchawaythatitsbackisflatandthere
arenoprojectionsbeyonditsbacksothatwhenthebevel
protractorisplacedonitsbackonasurfaceplatethere
shallbenoperceptiblerock.Theflatnessoftheworking
edgeofthestockandbodyistestedbycheckingthe
squarenessofbladewithrespecttostockwhenbladeisset
at90°.
Stock:
Theworkingedgeofthestockisabout90mmin
lengthand7mmthick.Itisveryessentialthatthe
workingedgeofthestockbeperfectlystraightandifat
alldepartureisthere,itshouldbeintheformof
concavityandoftheorderof0.01mmmaximumover
thewholespan.
Blade:
Itcanbemovedalongtheturretthroughoutitslength
andcanalsobereversed.Itisabout150or300mm
long,3mmwideand2mmthickandendsbevelledat
anglesof45°and60°withintheaccuracyof5minutes
ofarc.Itsworkingedgeshouldbestraightupto0.02
mmandparallelupto0.03mmovertheentirelengthof
300mm.Itcanbeclampedinanyposition.
Theworkingedgeofthestockisabout90mmin
lengthand7mmthick.Itisveryessentialthatthe
workingedgeofthestockbeperfectlystraightandifat
alldepartureisthere,itshouldbeintheformof
concavityandoftheorderof0.01mmmaximumover
thewholespan.
Blade:
Itcanbemovedalongtheturretthroughoutitslength
andcanalsobereversed.Itisabout150or300mm
long,3mmwideand2mmthickandendsbevelledat
anglesof45°and60°withintheaccuracyof5minutes
ofarc.Itsworkingedgeshouldbestraightupto0.02
mmandparallelupto0.03mmovertheentirelengthof
300mm.Itcanbeclampedinanyposition.
Acute angle attachment:
Itcanbereadilyfittedintobodyandclampedinany
position.Itsworkingedgeshouldbeflattowithin0.005
mmandparalleltotheworkingedgeofthestock
within0.015mmovertheentirelengthofattachment.
UseofBevelProtractors:
Itcanbereadilyfittedintobodyandclampedinany
position.Itsworkingedgeshouldbeflattowithin0.005
mmandparalleltotheworkingedgeofthestock
within0.015mmovertheentirelengthofattachment.
UseofBevelProtractors:
Sine Bar
Thesineprincipleusestheratioofthelengthoftwo
sidesofarighttriangleinderivingagivenangle.
Itmay,benotedthatdevicesoperatingonsine
principlearecapableof“selfgeneration”.
Themeasurementisusuallylimitedto45°fromloss
ofaccuracypointofview.
Thesinebarinitselfisnotacompletemeasuring
instrument.
Anotherdatumsuchasasurfaceplateisneeded,as
wellasotherauxiliaryequipment,notablyslip
gauges,andindicatingdevicetomake
measurements.
Sinebarsusedinconjunctionwithslipgauges
constituteaverygooddevicefortheprecise
measurementofangles.
Thesineprincipleusestheratioofthelengthoftwo
sidesofarighttriangleinderivingagivenangle.
Itmay,benotedthatdevicesoperatingonsine
principlearecapableof“selfgeneration”.
Themeasurementisusuallylimitedto45°fromloss
ofaccuracypointofview.
Thesinebarinitselfisnotacompletemeasuring
instrument.
Anotherdatumsuchasasurfaceplateisneeded,as
wellasotherauxiliaryequipment,notablyslip
gauges,andindicatingdevicetomake
measurements.
Sinebarsusedinconjunctionwithslipgauges
constituteaverygooddevicefortheprecise
measurementofangles.
Sinebarsareusedeithertomeasureanglesvery
accuratelyorforlocatinganyworktoagivenangle
withinverycloselimits.
Sinebarsaremadefromhighcarbon,high
chromium,corrosionresistantsteel,hardened,
groundandstabilised.
Twocylindersofequaldiameterareattachedatthe
ends.
Theaxesofthesetwocylindersaremutuallyparallel
toeachotherandalsoparalleltoandatequal
distancefromtheuppersurfaceofthesinebar.
Thedistancebetweentheaxesofthetwocylinders
isexactly5inchesor10inchesinBritishsystem,
and100,200and300mminmetricsystem.
Theaboverequirementsaremetandmaintainedby
takingduecareinthemanufactureofallparts.
accuratelyorforlocatinganyworktoagivenangle
withinverycloselimits.
Sinebarsaremadefromhighcarbon,high
chromium,corrosionresistantsteel,hardened,
groundandstabilised.
Twocylindersofequaldiameterareattachedatthe
ends.
Theaxesofthesetwocylindersaremutuallyparallel
toeachotherandalsoparalleltoandatequal
distancefromtheuppersurfaceofthesinebar.
Thedistancebetweentheaxesofthetwocylinders
isexactly5inchesor10inchesinBritishsystem,
and100,200and300mminmetricsystem.
Theaboverequirementsaremetandmaintainedby
takingduecareinthemanufactureofallparts.
The various parts are hardened and stabilised before
grinding and lapping.
All the working surfaces and the cylindrical surfaces
of the rollers are finished to surface finish of 0.2 µm
Ra value or better.
Depending upon the accuracy of the centre distance,
sine bars are graded as of A grade or B grade.
B grade of sine bars are guaranteed accurate upto
0.02 mm/m of lengthand A grade sine bars are more
accurate and guaranteed upto0.01mm/m of length.
Some holes are drilled in the body of the bar to
reduce the weight and to facilitate handling.
grinding and lapping.
All the working surfaces and the cylindrical surfaces
of the rollers are finished to surface finish of 0.2 µm
Ra value or better.
Depending upon the accuracy of the centre distance,
sine bars are graded as of A grade or B grade.
B grade of sine bars are guaranteed accurate upto
0.02 mm/m of lengthand A grade sine bars are more
accurate and guaranteed upto0.01mm/m of length.
Some holes are drilled in the body of the bar to
reduce the weight and to facilitate handling.
Different types of sine bars:
Constructional Features for Accurate
Measurement of sine bars:
(i)Thetworollersmusthaveequaldiameterandbe
truecylinders.
(ii)Therollersmustbesetparalleltoeachotherand
totheupperface.
(iii)Theprecisecentredistancebetweentherollers
mustbeknown.
(iv)Theupperfacemusthaveahighdegreeof
flatness.Thevariouscharacteristictoleranceshave
alreadybeenindicatedabove.
Measurement of sine bars:
(i)Thetworollersmusthaveequaldiameterandbe
truecylinders.
(ii)Therollersmustbesetparalleltoeachotherand
totheupperface.
(iii)Theprecisecentredistancebetweentherollers
mustbeknown.
(iv)Theupperfacemusthaveahighdegreeof
flatness.Thevariouscharacteristictoleranceshave
alreadybeenindicatedabove.
Use of Sine Bar
(1)Measuringknownanglesorlocatinganyworktoagiven
angle.
Forthispurposethesurfaceplateisassumedtobehavinga
perfectlyflatsurface,sothatitssurfacecouldbetreatedas
horizontal.Oneofthecylindersorrollersofsinebarisplaced
onthesurfaceplateandotherrollerisplacedontheslip
gaugesofheighth.
Letthesinebarbesetatanangleθ.Thensinθ=h/l,whereIis
thedistancebetweenthecenteroftherollers.Thusknowingθ,
hcanbefoundoutandanyworkcouldbesetatthisangleas
thetopfaceofsinebarisinclinedatangleθtothesurface
plate.
Theuseofangleplatesandclampscouldalsobemadein
caseofheavycomponents.
Forbetterresults,boththerollerscouldalsobeplacedonslip
gaugesofheighth1andh2respectively.Thensinθ=(h2–
h1)/l.
(1)Measuringknownanglesorlocatinganyworktoagiven
angle.
Forthispurposethesurfaceplateisassumedtobehavinga
perfectlyflatsurface,sothatitssurfacecouldbetreatedas
horizontal.Oneofthecylindersorrollersofsinebarisplaced
onthesurfaceplateandotherrollerisplacedontheslip
gaugesofheighth.
Letthesinebarbesetatanangleθ.Thensinθ=h/l,whereIis
thedistancebetweenthecenteroftherollers.Thusknowingθ,
hcanbefoundoutandanyworkcouldbesetatthisangleas
thetopfaceofsinebarisinclinedatangleθtothesurface
plate.
Theuseofangleplatesandclampscouldalsobemadein
caseofheavycomponents.
Forbetterresults,boththerollerscouldalsobeplacedonslip
gaugesofheighth1andh2respectively.Thensinθ=(h2–
h1)/l.
(2) Checking of unknown angles:
Manyatimes,angleofacomponenttobecheckedis
unknown.
Insuchacase,itisnecessarytofirstfindtheangle
approximatelywiththehelpofabevelprotractor.
Lettheanglebeθ.
Thenthesinebarissetatanangleθandclampedtoan
angleplate.
Next,theworkisplacedonsinebarandclampedto
angleplateasshowninFig.8.17andadialindicatoris
setatoneendoftheworkandmovedtotheother,and
deviationisnoted.
Againslipgaugesaresoadjusted(accordingtothis
deviation)thatdialindicatorreadszeroacrosswork
surface.
Manyatimes,angleofacomponenttobecheckedis
unknown.
Insuchacase,itisnecessarytofirstfindtheangle
approximatelywiththehelpofabevelprotractor.
Lettheanglebeθ.
Thenthesinebarissetatanangleθandclampedtoan
angleplate.
Next,theworkisplacedonsinebarandclampedto
angleplateasshowninFig.8.17andadialindicatoris
setatoneendoftheworkandmovedtotheother,and
deviationisnoted.
Againslipgaugesaresoadjusted(accordingtothis
deviation)thatdialindicatorreadszeroacrosswork
surface.
If deviation noted down by the dial indicator is δh
over a length l’ of work, then height of slip gauges by
which it should be adjusted in equal to = δh x l/I’.
over a length l’ of work, then height of slip gauges by
which it should be adjusted in equal to = δh x l/I’.
(3) Checking of unknown angles of heavy component:
Insuchcaseswherecomponentsareheavyandcan’tbe
mountedonthesinebar,thensinebarismountedonthe
componentasshowninFig.8.18.
Theheightovertherollerscanthenbemeasuredbya
vernierheightgauge;usingadialtestgaugemounted
ontheanvilofheightgaugeasthefiducialindicatorto
ensureconstantmeasuringpressure.
Theanvilonheightgaugeisadjustedwithprobeofdial
testgaugeshowingsamereadingforthetopmost
positionofrollersofsinebar.
Fig.8.18showstheuseofheightgaugeforobtainingtwo
readingsforeitheroftherollerofsinebar.
Thedifferenceofthetworeadingsofheightgauge
dividedbythecentredistanceofsinebargivesthesine
oftheangleofthecomponenttobemeasured.
Insuchcaseswherecomponentsareheavyandcan’tbe
mountedonthesinebar,thensinebarismountedonthe
componentasshowninFig.8.18.
Theheightovertherollerscanthenbemeasuredbya
vernierheightgauge;usingadialtestgaugemounted
ontheanvilofheightgaugeasthefiducialindicatorto
ensureconstantmeasuringpressure.
Theanvilonheightgaugeisadjustedwithprobeofdial
testgaugeshowingsamereadingforthetopmost
positionofrollersofsinebar.
Fig.8.18showstheuseofheightgaugeforobtainingtwo
readingsforeitheroftherollerofsinebar.
Thedifferenceofthetworeadingsofheightgauge
dividedbythecentredistanceofsinebargivesthesine
oftheangleofthecomponenttobemeasured.
Where greater accuracy is required, the position of
dial test gauge probe can be sensed by adjusting a
pile of slip gauges till dial indicator indicates same
reading over roller of sine bar and the slip gauges.
dial test gauge probe can be sensed by adjusting a
pile of slip gauges till dial indicator indicates same
reading over roller of sine bar and the slip gauges.
Limitations of Sine Bars:
Theestablishmentofanglebythesineprincipleis
essentiallyalengthmeasuringprocess.
Thustheaccuracy,inpractice,islimitedbymeasurement
ofcentredistanceoftwoprecisionrollers.
Thegeometricalconditioninvolvedinmeasuringthe
exact,effectivecentredistanceexistingbetweentwo
rollersofthesinebartoacertaintyoffractionofaµmis
aninfinitelycomplexproblem.
Thisfundamentallimitationaloneprecludestheuseof
thesinebarasaprimarystandardofangle.
Devicesoperatingonthesineprinciplearefairlyreliable
atangleslessthan15°,butbecomeincreasingly
inaccurateastheangleincreases.
Sinebarsinherentlybecomeincreasinglyimpracticaland
inaccurateastheangleexceeds45°.
Theestablishmentofanglebythesineprincipleis
essentiallyalengthmeasuringprocess.
Thustheaccuracy,inpractice,islimitedbymeasurement
ofcentredistanceoftwoprecisionrollers.
Thegeometricalconditioninvolvedinmeasuringthe
exact,effectivecentredistanceexistingbetweentwo
rollersofthesinebartoacertaintyoffractionofaµmis
aninfinitelycomplexproblem.
Thisfundamentallimitationaloneprecludestheuseof
thesinebarasaprimarystandardofangle.
Devicesoperatingonthesineprinciplearefairlyreliable
atangleslessthan15°,butbecomeincreasingly
inaccurateastheangleincreases.
Sinebarsinherentlybecomeincreasinglyimpracticaland
inaccurateastheangleexceeds45°.
Thesinebarsinherentlybecomeincreasinglyimpractical
andinaccurateastheangleexceeds45°becauseof
followingreasons:
—Thesinebarisphysicallyclumsytoholdinposition.
—Thebodyofthesinebarobstructsthegaugeblock
stack,evenifrelieved.
—Slighterrorsofthesinebarcauselargeangular
errors.
—Longgaugestacksarenotnearlyasaccurateas
shortergaugeblocks.
—Temperaturevariationbecomesmorecritical.
—Adifferenceindeformationoccursatthepointofroller
contacttothesupportsurfaceandtothegaugeblocks,
becauseathigherangles,theweightloadisshiftedmore
towardthefulcrumroller.
—Thesizeofgauges,instrumentsorpartsthatasine
barcaninspectislimited,sinceitisnotdesignedto
supportlargeorheavyobjects.
andinaccurateastheangleexceeds45°becauseof
followingreasons:
—Thesinebarisphysicallyclumsytoholdinposition.
—Thebodyofthesinebarobstructsthegaugeblock
stack,evenifrelieved.
—Slighterrorsofthesinebarcauselargeangular
errors.
—Longgaugestacksarenotnearlyasaccurateas
shortergaugeblocks.
—Temperaturevariationbecomesmorecritical.
—Adifferenceindeformationoccursatthepointofroller
contacttothesupportsurfaceandtothegaugeblocks,
becauseathigherangles,theweightloadisshiftedmore
towardthefulcrumroller.
—Thesizeofgauges,instrumentsorpartsthatasine
barcaninspectislimited,sinceitisnotdesignedto
supportlargeorheavyobjects.
Precautions in use of sine bars.
(i)Thesinebarshouldnotbeusedforanglegreater
than60°becauseanypossibleerrorinconstruction
isaccentuatedatthislimit.(AlsoreferProb.8.2).
(ii)Acompoundangleshouldnotbeformedbymis-
aligningofworkpiecewiththesinebar.Thiscanbe
avoidedbyattachingthesinebarandworkagainst
anangleplate.
(iii)Accuracyofsinebarshouldbeensured.
(iv)Asfaraspossiblelongersinebarshouldbeused
sincemanyerrorsarereducedbyusinglongersine
bars.
(i)Thesinebarshouldnotbeusedforanglegreater
than60°becauseanypossibleerrorinconstruction
isaccentuatedatthislimit.(AlsoreferProb.8.2).
(ii)Acompoundangleshouldnotbeformedbymis-
aligningofworkpiecewiththesinebar.Thiscanbe
avoidedbyattachingthesinebarandworkagainst
anangleplate.
(iii)Accuracyofsinebarshouldbeensured.
(iv)Asfaraspossiblelongersinebarshouldbeused
sincemanyerrorsarereducedbyusinglongersine
bars.
Sine Table.
Thisisthedevelopmentofthesinebarandtheprocedureofsetting
itatanyangleissameasforsinebars.
Thesinetableisthemostconvenientandaccuratedesignforheavy
workpiece.
Thetableisquiteruggedoneandtheweightofunitandworkpieceis
givenfullerandsafersupport.
Thegaugingplatformsareself-containedandcanbehighlyrefined.
Thetablemaybesafelyswungtoanyanglefrom0°to90°by
pivotingitaboutitshingedend.
Twosetsofsturdynon-influencingclampsareprovidedfor
supportingthetableonbothsidesoverthewholerangeofsinetable.
Itmaybenotedthatthetableisalonglevelwhichbendsandtwists
whenputthroughvariousangleswhilesupportingallsortsofshapes,
sizesandweightsofworkpieces.
Theclampingmechanismofthesinetablemayalsocausedistortion,
varyingtheanglesetslightly.
Howevertheerrorsduetothesearenotgenerallylarge.
Thisisthedevelopmentofthesinebarandtheprocedureofsetting
itatanyangleissameasforsinebars.
Thesinetableisthemostconvenientandaccuratedesignforheavy
workpiece.
Thetableisquiteruggedoneandtheweightofunitandworkpieceis
givenfullerandsafersupport.
Thegaugingplatformsareself-containedandcanbehighlyrefined.
Thetablemaybesafelyswungtoanyanglefrom0°to90°by
pivotingitaboutitshingedend.
Twosetsofsturdynon-influencingclampsareprovidedfor
supportingthetableonbothsidesoverthewholerangeofsinetable.
Itmaybenotedthatthetableisalonglevelwhichbendsandtwists
whenputthroughvariousangleswhilesupportingallsortsofshapes,
sizesandweightsofworkpieces.
Theclampingmechanismofthesinetablemayalsocausedistortion,
varyingtheanglesetslightly.
Howevertheerrorsduetothesearenotgenerallylarge.
Thesinetableiscapableofexceptionalaccuracyifuseruses
itproperly,constructionprinciplesandallelementsofsine
tablearecorrect,thegaugeblockstackiscorrectandatsame
temperatureassinetable.
Thesinetableshouldbeelevatedorlowered,usingthefine
adjustmentfeaturetoattainthedesired“feel”betweenthe
gaugeblocksandpinsofbothsidesseparately.
Afurtherdevelopmentofthisisthecompoundsinetablein
whichtwosinetableshavingtheiraxesoftiltsetatright
anglestoeachotherareprovided.
Thesetwotablesaremountedonacommonbaseandthe
tablecanbesetatcompoundanglebyresolvingthis
compoundangleintoitsindividualanglesintwoplanesatright
anglestoeachotherandsettingeachtableaccordingly.
The“doublesine”principleemploysgaugepinsratherthan
gaugingplatforminbothtableandbaseofthesinetable.
Thisdesignallowsangularsettingstoafull90°,andminimises
theerrorsnormallyinherentinasinetableatgreaterangles.
itproperly,constructionprinciplesandallelementsofsine
tablearecorrect,thegaugeblockstackiscorrectandatsame
temperatureassinetable.
Thesinetableshouldbeelevatedorlowered,usingthefine
adjustmentfeaturetoattainthedesired“feel”betweenthe
gaugeblocksandpinsofbothsidesseparately.
Afurtherdevelopmentofthisisthecompoundsinetablein
whichtwosinetableshavingtheiraxesoftiltsetatright
anglestoeachotherareprovided.
Thesetwotablesaremountedonacommonbaseandthe
tablecanbesetatcompoundanglebyresolvingthis
compoundangleintoitsindividualanglesintwoplanesatright
anglestoeachotherandsettingeachtableaccordingly.
The“doublesine”principleemploysgaugepinsratherthan
gaugingplatforminbothtableandbaseofthesinetable.
Thisdesignallowsangularsettingstoafull90°,andminimises
theerrorsnormallyinherentinasinetableatgreaterangles.
Compound Sine Table:
Sine Center:
Used in situations where it is difficult to mount the
component on the sine bar.
On the top surface, it consists of two blocks which
carry two centers which can be clamped at any
position on the sine bar.
The two centers can be adjusted depending upon
the length of the conical component.
These are used uptoinclination of 60°.
Used in situations where it is difficult to mount the
component on the sine bar.
On the top surface, it consists of two blocks which
carry two centers which can be clamped at any
position on the sine bar.
The two centers can be adjusted depending upon
the length of the conical component.
These are used uptoinclination of 60°.
Auto Collimator:
This is an optical instrument used for the
measurement of small angular differences.
For small angular measurements, autocollimator
provides a very sensitive and accurate approach.
Auto-collimator is essentially an infinity telescope
and a collimator combined into one instrument.
This is an optical instrument used for the
measurement of small angular differences.
For small angular measurements, autocollimator
provides a very sensitive and accurate approach.
Auto-collimator is essentially an infinity telescope
and a collimator combined into one instrument.
Principle of Autocollimator
Acrossline“target”graticuleispositionedatthefocal
planeofatelescopeobjectivesystemwiththe
intersectionofthecrosslineontheopticalaxis,i.e.at
theprincipalfocus.
Whenthetargetgraticuleisilluminated,raysoflight
divergingfromtheintersectionpointreachthe
objectiveviaabeamsplitterandareprojectedfrom
theobjectiveasparallelpencilsoflight.Inthismode,
theopticalsystemisoperatingasa“collimator”.
Acrossline“target”graticuleispositionedatthefocal
planeofatelescopeobjectivesystemwiththe
intersectionofthecrosslineontheopticalaxis,i.e.at
theprincipalfocus.
Whenthetargetgraticuleisilluminated,raysoflight
divergingfromtheintersectionpointreachthe
objectiveviaabeamsplitterandareprojectedfrom
theobjectiveasparallelpencilsoflight.Inthismode,
theopticalsystemisoperatingasa“collimator”.
Aflatreflectorplacedinfrontoftheobjectiveand
exactlynormaltotheopticalaxisreflectstheparallel
pencilsoflightbackalongtheiroriginalpaths.
Theyarethenbroughttofocusintheplaneofthe
targetgraticuleandexactlycoincidentwithits
intersection.
Aproportionofthereturnedlightpassesstraight
throughthebeamsplitterandthereturnimageofthe
targetcrosslineisthereforevisiblethroughthe
eyepiece.
exactlynormaltotheopticalaxisreflectstheparallel
pencilsoflightbackalongtheiroriginalpaths.
Theyarethenbroughttofocusintheplaneofthe
targetgraticuleandexactlycoincidentwithits
intersection.
Aproportionofthereturnedlightpassesstraight
throughthebeamsplitterandthereturnimageofthe
targetcrosslineisthereforevisiblethroughthe
eyepiece.
Inthismode,theopticalsystemisoperatingasa
telescopefocusedatinfinity.
Ifthereflectoristiltedthroughasmallanglethereflected
pencilsoflightwillbedeflectedbytwicetheangleoftilt
(principleofreflection)andwillbebroughttofocusinthe
planeofthetargetgraticulebutlinearlydisplacedfrom
theactualtargetcrosslinesbyanamount2θxf.
Lineardisplacementofthegraticuleimageintheplaneof
theeyepieceisthereforedirectlyproportionaltoreflector
tiltandcanbemeasuredbyaneyepiecegraticule,optical
micrometerorelectronicdetectorsystem,scaleddirectly
inangularunits.
Theautocollimatorissetpermanentlyatinfinityfocusand
nodeviceforfocusingadjustmentfordistanceisprovided
ordesirable.
Itrespondsonlytoreflectortilt(notlateraldisplacement
ofthereflector).
Thisisindependentofseparationbetweenthereflector
andtheautocollimator,assumingnoatmospheric
disturbanceandtheuseofaperfectlyflatreflector.
telescopefocusedatinfinity.
Ifthereflectoristiltedthroughasmallanglethereflected
pencilsoflightwillbedeflectedbytwicetheangleoftilt
(principleofreflection)andwillbebroughttofocusinthe
planeofthetargetgraticulebutlinearlydisplacedfrom
theactualtargetcrosslinesbyanamount2θxf.
Lineardisplacementofthegraticuleimageintheplaneof
theeyepieceisthereforedirectlyproportionaltoreflector
tiltandcanbemeasuredbyaneyepiecegraticule,optical
micrometerorelectronicdetectorsystem,scaleddirectly
inangularunits.
Theautocollimatorissetpermanentlyatinfinityfocusand
nodeviceforfocusingadjustmentfordistanceisprovided
ordesirable.
Itrespondsonlytoreflectortilt(notlateraldisplacement
ofthereflector).
Thisisindependentofseparationbetweenthereflector
andtheautocollimator,assumingnoatmospheric
disturbanceandtheuseofaperfectlyflatreflector.
Manyfactorsgovernthespecificationofanautocollimator,in
particularitsfocallengthanditseffectiveaperture.
Thefocallengthdeterminesbasicsensitivityandangular
measuringrange.
Thelongerthefocallengththelargeristhelinear
displacementforagivenreflectortilt,butthemaximum
reflectortiltwhichcanbeaccommodatedisconsequently
reduced.
Sensitivityisthereforetradedagainstmeasuringrange.
Themaximum separationbetweenreflectorand
autocollimator,or“workingdistance”,isgovernedbythe
effectiveapertureoftheobjective,andtheangularmeasuring
rangeoftheinstrumentbecomesreducedatlongworking
distances.Increasingthemaximumworkingdistanceby
increasingtheeffectiveaperturethendemandsalarger
reflectorforsatisfactoryimagecontrast.
Autocollimatordesignthusinvolvesmanyconflictingcriteria
andforthisreasonarangeofinstrumentsisrequiredto
optimallycovereveryapplication.
particularitsfocallengthanditseffectiveaperture.
Thefocallengthdeterminesbasicsensitivityandangular
measuringrange.
Thelongerthefocallengththelargeristhelinear
displacementforagivenreflectortilt,butthemaximum
reflectortiltwhichcanbeaccommodatedisconsequently
reduced.
Sensitivityisthereforetradedagainstmeasuringrange.
Themaximum separationbetweenreflectorand
autocollimator,or“workingdistance”,isgovernedbythe
effectiveapertureoftheobjective,andtheangularmeasuring
rangeoftheinstrumentbecomesreducedatlongworking
distances.Increasingthemaximumworkingdistanceby
increasingtheeffectiveaperturethendemandsalarger
reflectorforsatisfactoryimagecontrast.
Autocollimatordesignthusinvolvesmanyconflictingcriteria
andforthisreasonarangeofinstrumentsisrequiredto
optimallycovereveryapplication.
Aircurrentsintheopticalpathbetweenthe
autocollimatorandthetargetmirrorcause
fluctuationsinthereadingsobtained.
Thiseffectismorepronouncedasdistancefrom
autocollimatortotargetmirrorincreases.
Furthererrorsmayalsooccurduetoerrorsin
flatnessandreflectivityofthetargetmirrorwhich
shouldbeofhighquality.
Whenboththeautocollimatorandthetargetmirror
gaugecanremainfixed,extremelyclosereadings
maybetakenandrepeatabilityisexcellent.
Whenanyofthesehastobemoved,greatcareis
required.
autocollimatorandthetargetmirrorcause
fluctuationsinthereadingsobtained.
Thiseffectismorepronouncedasdistancefrom
autocollimatortotargetmirrorincreases.
Furthererrorsmayalsooccurduetoerrorsin
flatnessandreflectivityofthetargetmirrorwhich
shouldbeofhighquality.
Whenboththeautocollimatorandthetargetmirror
gaugecanremainfixed,extremelyclosereadings
maybetakenandrepeatabilityisexcellent.
Whenanyofthesehastobemoved,greatcareis
required.
Autocollimator Applications:
Autocollimatorsareappliedtothemeasurementof
straightnessandflatness;preciseangularindexingin
conjuctionwithpolygons;comparativemeasurementusing
masterangles;assessmentofsquarenessandparallelismof
components;andthemeasurementofsmalllinear
dimensions.
Straightnessismeasuredinconjunctionwithareflector
attachedtoabasehavingtwoco-planarlocatingpadsata
knowndistanceapart.
Thebaseissteppedinastraightlinealongthesurfaceat
intervalsequaltothepitchofthelocatingpadsandthe
angularchangeisrecordedateachposition.
Thesereadingsarereadilyconvertedintochangesinvertical
heightoftheleadingpad.
Aplotofthesurfacestraightnesscanthenbepreparedfrom
thedata.
Measurementofflatnessisanextensionofthismethodand
involvesaseriesofstraightnessmeasurementsalongstraight
lineaxesacrossthesurface.
Autocollimatorsareappliedtothemeasurementof
straightnessandflatness;preciseangularindexingin
conjuctionwithpolygons;comparativemeasurementusing
masterangles;assessmentofsquarenessandparallelismof
components;andthemeasurementofsmalllinear
dimensions.
Straightnessismeasuredinconjunctionwithareflector
attachedtoabasehavingtwoco-planarlocatingpadsata
knowndistanceapart.
Thebaseissteppedinastraightlinealongthesurfaceat
intervalsequaltothepitchofthelocatingpadsandthe
angularchangeisrecordedateachposition.
Thesereadingsarereadilyconvertedintochangesinvertical
heightoftheleadingpad.
Aplotofthesurfacestraightnesscanthenbepreparedfrom
thedata.
Measurementofflatnessisanextensionofthismethodand
involvesaseriesofstraightnessmeasurementsalongstraight
lineaxesacrossthesurface.
Spirit Level
Itisgenerallythoughtthatspiritlevelisusedonlyfor
thestaticlevellingofthemachineryandother
equipment.
Butcalibratedspiritlevelisanangularmeasuring
deviceofgreatprecision.
Spiritlevelisnothingbutsimplyaglasstube,the
boreofwhichisgroundtoalargeradius.
Itisobviousthat,iftheliquidalmostfillsthetube,the
bubbleinliquidwillalwayslieatthehighestposition
inthetube.
Ifthetubeistiltedthroughasmallanglethebubble
willmovealongtheradiusofthetubethrougha
certaindistancedependingontheangleofthetilt.
thestaticlevellingofthemachineryandother
equipment.
Butcalibratedspiritlevelisanangularmeasuring
deviceofgreatprecision.
Spiritlevelisnothingbutsimplyaglasstube,the
boreofwhichisgroundtoalargeradius.
Itisobviousthat,iftheliquidalmostfillsthetube,the
bubbleinliquidwillalwayslieatthehighestposition
inthetube.
Ifthetubeistiltedthroughasmallanglethebubble
willmovealongtheradiusofthetubethrougha
certaindistancedependingontheangleofthetilt.
Thesensitivityofaspiritlevelisexpressedastheangleoftilt
insecondsforwhichbubblewillmovebyonedivisiononthe
tube.
Onedivisionisgenerallyabout2.5mminlength.
Thussensitivity=
??????��??????�??????��������
1�??????�??????�??????��������
NowifRistheradiusofthetube,andIisthedistanceby
whichthegraduationsareseparated,i.e.thelengthofone
division,thentheangleoftiltθcorrespondingto1division
movementofbubblewillbegivenbyθ=l/R.
Generallythegraduationsareat2.5mmintervalsandthese
representatiltof10secondsofarc,i.esensitivityoflevel
desiredis10secper2.5mmmovementofbubble.
Then10sec=0.0000485radian=2.5mm/RorR=
25/0.0000485=51500mm,orR=51.5mapprox.
Thusfortheabovesensitivity,radiusofthetubeorvialmust
beabout51.5manditisobviousnowthatsensitivityofthe
spiritlevelisgovernedsolelybytheradiusofthetubeandthe
baselengthofitsmount.
insecondsforwhichbubblewillmovebyonedivisiononthe
tube.
Onedivisionisgenerallyabout2.5mminlength.
Thussensitivity=
??????��??????�??????��������
1�??????�??????�??????��������
NowifRistheradiusofthetube,andIisthedistanceby
whichthegraduationsareseparated,i.e.thelengthofone
division,thentheangleoftiltθcorrespondingto1division
movementofbubblewillbegivenbyθ=l/R.
Generallythegraduationsareat2.5mmintervalsandthese
representatiltof10secondsofarc,i.esensitivityoflevel
desiredis10secper2.5mmmovementofbubble.
Then10sec=0.0000485radian=2.5mm/RorR=
25/0.0000485=51500mm,orR=51.5mapprox.
Thusfortheabovesensitivity,radiusofthetubeorvialmust
beabout51.5manditisobviousnowthatsensitivityofthe
spiritlevelisgovernedsolelybytheradiusofthetubeandthe
baselengthofitsmount.
Letthebaselengthofanyspiritlevelbeabout250mm,thenthe
heighthbywhichoneendmustberaisedfor2.5mmbubble
movementisgivenby0.0000485=A/250orh=0.0121mm.
Ifthebaselengthbereducedto125mm,thensensitivityis
increasedtwice,andinthiscaseeachgraduationrepresents
0.006mm.
Theaccuracyofaspiritleveldependsuponthesettingofthetube
relativetothebase.
Inallthehighersensitivitylevelsthetubeismounted
kinematicallyinthebody,oneendofthetuberestingonacone
whichformsapartoftheadjustingscrew.
Thuswiththehelpofthisfinepitchscrew,itiscapableof
adjustment.Althoughitisnowpossibletoadjustthetubesuch
thatbubbleshowsthesamereadingsonahorizontalsurface,
evenwhenthelevelisreversed.
Butintakingprecisemeasurement,itshouldbeassumedthat
someerrorexistsandtworeadingsmustbetakenalongthe
samelinebyreversingthelevel.
Themeanofthesetworeadingswillindicatethetruedeflectionof
bubble.
heighthbywhichoneendmustberaisedfor2.5mmbubble
movementisgivenby0.0000485=A/250orh=0.0121mm.
Ifthebaselengthbereducedto125mm,thensensitivityis
increasedtwice,andinthiscaseeachgraduationrepresents
0.006mm.
Theaccuracyofaspiritleveldependsuponthesettingofthetube
relativetothebase.
Inallthehighersensitivitylevelsthetubeismounted
kinematicallyinthebody,oneendofthetuberestingonacone
whichformsapartoftheadjustingscrew.
Thuswiththehelpofthisfinepitchscrew,itiscapableof
adjustment.Althoughitisnowpossibletoadjustthetubesuch
thatbubbleshowsthesamereadingsonahorizontalsurface,
evenwhenthelevelisreversed.
Butintakingprecisemeasurement,itshouldbeassumedthat
someerrorexistsandtworeadingsmustbetakenalongthe
samelinebyreversingthelevel.
Themeanofthesetworeadingswillindicatethetruedeflectionof
bubble.
Relations between movement of bubble & other conditions involved:
Inthefig,Bisthetopofthetuberadiusandtheposition
ofthebubblewhenthebaseisatOA(horizontal).
Ifthebaseistiltedthroughanangleαandbaseoccupies
positionOA’,thebubblewillmoveadistanceltoB’,
whereangleBOB’=α.
IfRistheradiusofthetubethen,arcl=Rα=>α=
���??????
??????
IfListhelengthofthebaseandhisthedifferencein
heightbetweenitsends,thenforsmallvalueofh,
h=Lα=>α=
ℎ
??????
Therefore,equatingα,weget
���??????
??????
=
ℎ
??????
&arcl=
??????ℎ
??????
ofthebubblewhenthebaseisatOA(horizontal).
Ifthebaseistiltedthroughanangleαandbaseoccupies
positionOA’,thebubblewillmoveadistanceltoB’,
whereangleBOB’=α.
IfRistheradiusofthetubethen,arcl=Rα=>α=
���??????
??????
IfListhelengthofthebaseandhisthedifferencein
heightbetweenitsends,thenforsmallvalueofh,
h=Lα=>α=
ℎ
??????
Therefore,equatingα,weget
���??????
??????
=
ℎ
??????
&arcl=
??????ℎ
??????
To convert 1 radian to 1̊ :
Is given by=
180̊
π
To convert 1 radian to 1̊ :
Is given by 3600.
Therefore, 1 radian =
206,265”(s) of an arc.
Ifαistakeninseconds,then,l=
??????α
206,265
i.e.oneradianequals206,265ofan
arc.
Fromtheaboveequation,itisobvious
thatsensitivityofthelevelincreasesas
Rincreases.
Thescalespacingorthedistance
betweenadjacentgraduationis
generallyabout2mmandthusfor
R=206m,then
α=
2??????206,265
206,000
≈2s.
Is given by=
180̊
π
To convert 1 radian to 1̊ :
Is given by 3600.
Therefore, 1 radian =
206,265”(s) of an arc.
Ifαistakeninseconds,then,l=
??????α
206,265
i.e.oneradianequals206,265ofan
arc.
Fromtheaboveequation,itisobvious
thatsensitivityofthelevelincreasesas
Rincreases.
Thescalespacingorthedistance
betweenadjacentgraduationis
generallyabout2mmandthusfor
R=206m,then
α=
2??????206,265
206,000
≈2s.
Theinclinationof2”causesbubblemovementof2mm.
Thisisthesensitivespiritlevelandisrecommendedfor
researchlaboratory.
Forhighlypreciseshopmeasurements,spiritlevelswith
scaledivisionvalueof4to10areemployed.
Forordinarypurposes,scaledivisionvaluesoforderof10
to40aresufficient.
Itshouldbenotedthatspiritlevelsareverysensitiveto
variationintemperatureoftheirsurroundings,sincethey
changethetensionoftheethervapoursinthetube.Hence,
theymustbeusedincontrolledroomtemperature.
Thisisthesensitivespiritlevelandisrecommendedfor
researchlaboratory.
Forhighlypreciseshopmeasurements,spiritlevelswith
scaledivisionvalueof4to10areemployed.
Forordinarypurposes,scaledivisionvaluesoforderof10
to40aresufficient.
Itshouldbenotedthatspiritlevelsareverysensitiveto
variationintemperatureoftheirsurroundings,sincethey
changethetensionoftheethervapoursinthetube.Hence,
theymustbeusedincontrolledroomtemperature.
Types of Spirit Levels:
Type 1: Base length from 100 to 200 mm. Made of steel,
hardened and lapped to a good surface finish at the
bottom.
Type 2: Base length from 250 to 500 mm. Made of cast
iron or steel body with a 120̊ vee groove, hardened and
lapped to a good surface finish at the bottom.
Type 3: Base length from 200 mm square block. Made of
cast iron or steel body with a 120̊ vee groove, hardened
and lapped to a good surface finish at the bottom.
Type 1: Base length from 100 to 200 mm. Made of steel,
hardened and lapped to a good surface finish at the
bottom.
Type 2: Base length from 250 to 500 mm. Made of cast
iron or steel body with a 120̊ vee groove, hardened and
lapped to a good surface finish at the bottom.
Type 3: Base length from 200 mm square block. Made of
cast iron or steel body with a 120̊ vee groove, hardened
and lapped to a good surface finish at the bottom.
Characteristic Elements of a Level
Thecharacteristicelementsofalevelaretheradiusof
curvatureofthetubewhichdecidesitssensitiveness,andthe
distancebetweenthetwoconsecutivelinesonitsscale.
Sensitivity.Itisdefinedasthedisplacementofthebubblefora
tiltof1mmin1morfor200secondsofarc.
Constantofspiritlevel.Itisthechangeintilt,expressedinmm
perm(orinsecondsofarc),whichproducesadisplacement
ofthebubblebyonedivision.Constantoflevel=lengthinmm
ofonedivisionofscale/sensitivity
Accuracyoflevel.Inorderthatspiritlevelbeaccurate,itsbase
shouldbeflatwithinprescribedlimits.Itisexpressedbythe
movementofbubblebyadivisionforagivenchangeofangle.
Usuallyitis1divisionforachangeofangleof0.05mmper
metre.
Errors.Itcouldbeduetoerrorintheviallikeradiusof
curvaturebeingnon-uniform,orvialorscalebeingpositioned
incorrectly.Errorscouldalsocreepinduetoincorrectuseof
level.Temperaturevariationalsoinfluencesreadingsandfor
this,repeatedreadingsshouldbetaken.
Thecharacteristicelementsofalevelaretheradiusof
curvatureofthetubewhichdecidesitssensitiveness,andthe
distancebetweenthetwoconsecutivelinesonitsscale.
Sensitivity.Itisdefinedasthedisplacementofthebubblefora
tiltof1mmin1morfor200secondsofarc.
Constantofspiritlevel.Itisthechangeintilt,expressedinmm
perm(orinsecondsofarc),whichproducesadisplacement
ofthebubblebyonedivision.Constantoflevel=lengthinmm
ofonedivisionofscale/sensitivity
Accuracyoflevel.Inorderthatspiritlevelbeaccurate,itsbase
shouldbeflatwithinprescribedlimits.Itisexpressedbythe
movementofbubblebyadivisionforagivenchangeofangle.
Usuallyitis1divisionforachangeofangleof0.05mmper
metre.
Errors.Itcouldbeduetoerrorintheviallikeradiusof
curvaturebeingnon-uniform,orvialorscalebeingpositioned
incorrectly.Errorscouldalsocreepinduetoincorrectuseof
level.Temperaturevariationalsoinfluencesreadingsandfor
this,repeatedreadingsshouldbetaken.
Now-a-dayselectroniclevelshavebeendeveloped
inwhichaplatehangsfromtopofinstrumentandon
horizontalplaneitliesexactlymidwaybetweentwo
fixedparallelplates.
Onevenminuteinclinedsurfacetheplatehungfrom
topwillbetiltedandgapbetweenthisplateand
othertwoplateswillchange.
Thischangeisdetectedbyelectricalcircuitsandis
calibratedintermsoftheangleofinclination.
Somedampingisalsoprovidedinmovementof
freelyhangingplatesothatitattainsequilibrium
positionquicklyanddoesnotkeeponoscillatinglike
apendulum.
inwhichaplatehangsfromtopofinstrumentandon
horizontalplaneitliesexactlymidwaybetweentwo
fixedparallelplates.
Onevenminuteinclinedsurfacetheplatehungfrom
topwillbetiltedandgapbetweenthisplateand
othertwoplateswillchange.
Thischangeisdetectedbyelectricalcircuitsandis
calibratedintermsoftheangleofinclination.
Somedampingisalsoprovidedinmovementof
freelyhangingplatesothatitattainsequilibrium
positionquicklyanddoesnotkeeponoscillatinglike
apendulum.
Clinometer:
A clinometer is a special case of the application of spirit level.
In clinometer, the spirit level is mounted on a rotary member
carried in a housing.
One face of the housing forms the base of the instrument.
On the housing, there is a circular scale.
The angle of inclination of the rotary member carrying the level
relative to its base can be measured by this circular scale.
The clinometer is mainly used to determine the included angle
of two adjacent faces of workpiece.
Thus for this purpose, the instrument base is placed on one
face and the rotary body adjusted till zero reading of the
bubble is obtained.
The angle of rotation is then noted on the circular scale
against the index.
A second reading is then taken in the similar manner on the
second face of workpiece.
The included angle between the faces is then the difference
between the two readings.
In clinometer, the spirit level is mounted on a rotary member
carried in a housing.
One face of the housing forms the base of the instrument.
On the housing, there is a circular scale.
The angle of inclination of the rotary member carrying the level
relative to its base can be measured by this circular scale.
The clinometer is mainly used to determine the included angle
of two adjacent faces of workpiece.
Thus for this purpose, the instrument base is placed on one
face and the rotary body adjusted till zero reading of the
bubble is obtained.
The angle of rotation is then noted on the circular scale
against the index.
A second reading is then taken in the similar manner on the
second face of workpiece.
The included angle between the faces is then the difference
between the two readings.
Precision MicropticClinometer
Theseareusedformeasurementandcheckingof:
angularfaces,gauges,reliefanglesonlargecutting
tools,angleofmillingcutterinserts,jigsandfixtures,
levelsofmachinewaysandbedplates,andforsettingof
inclinabletablesonjigboringmachines,andadjustable
angleplates,angularworkongrindingandlapping
machines.
Withtheappropriateaccessoriesthesecanbeusedfor
measuringangulardisplacementsofsmallparts,and
settingoutangles.
Thespecialfeaturesofprecisionmicropticclinometerare
directreadingovertherange0°—360°,opticalreading
system;totallyenclosedglasscirclesandeasy-to-read
scales;mainscaleandmicrometerscalevisible
simultaneouslyintheeyepieceexternalscaleforrapid
coarsesetting,slowmotionscrewforfinesetting,
eyepiecerotatabletomostconvenientviewingposition,
andhardenedgroundsteelbase.
Theseareusedformeasurementandcheckingof:
angularfaces,gauges,reliefanglesonlargecutting
tools,angleofmillingcutterinserts,jigsandfixtures,
levelsofmachinewaysandbedplates,andforsettingof
inclinabletablesonjigboringmachines,andadjustable
angleplates,angularworkongrindingandlapping
machines.
Withtheappropriateaccessoriesthesecanbeusedfor
measuringangulardisplacementsofsmallparts,and
settingoutangles.
Thespecialfeaturesofprecisionmicropticclinometerare
directreadingovertherange0°—360°,opticalreading
system;totallyenclosedglasscirclesandeasy-to-read
scales;mainscaleandmicrometerscalevisible
simultaneouslyintheeyepieceexternalscaleforrapid
coarsesetting,slowmotionscrewforfinesetting,
eyepiecerotatabletomostconvenientviewingposition,
andhardenedgroundsteelbase.
PrecisionMicropticClinometerutilisesbubbleunit
withaprismaticcoincidencereaderwhichpresents
bothendsofthebubbleasadjacentimagesinasplit
fieldofview.
Asthevialislevelled,thetwohalf-imagesmoveinto
coincidence,makingitveryeasytoseewhenthe
bubbleisexactlycentered,withoutreferencetoany
graduations.
withaprismaticcoincidencereaderwhichpresents
bothendsofthebubbleasadjacentimagesinasplit
fieldofview.
Asthevialislevelled,thetwohalf-imagesmoveinto
coincidence,makingitveryeasytoseewhenthe
bubbleisexactlycentered,withoutreferencetoany
graduations.
Todeterminetheinclinationoftheclinometer,the
bubbleunitislevelledandthescalesread.
Onlookingthroughthereadereyepiece,three
aperturescanbeseen.
Theupperaperturecontainstwopairsofdouble
linesandtwosinglelines.
Tosetthemicrometer,theknobisturneduntilthe
singlelineisbroughtexactlycentralbetweenthe
doublelines.
Thescalescanthenberead,therequiredangle
beingthesumofthereadingsofthemainscaleand
themicrometerscale.[ReferFig.8.29].
bubbleunitislevelledandthescalesread.
Onlookingthroughthereadereyepiece,three
aperturescanbeseen.
Theupperaperturecontainstwopairsofdouble
linesandtwosinglelines.
Tosetthemicrometer,theknobisturneduntilthe
singlelineisbroughtexactlycentralbetweenthe
doublelines.
Thescalescanthenberead,therequiredangle
beingthesumofthereadingsofthemainscaleand
themicrometerscale.[ReferFig.8.29].
The double lines are imaged from one side of the circle
and the single ones from a point diametrically opposite ;
by using the double lines as an index for the single line,
any residual centring error of the circle is cancelled out.
The scales are illuminated by an intergrallow voltage
lamp.
The bubble unit is daylight illuminated, but is also
provided with a lamp for alternative illumination.
A locating face on the back allows the instrument to be
used horizontally with the accessory worktable or
reflector unit.
The reference for inclination is the bubble vial. In order to
measure the inclination of a surface, the vial—to which
the circle is attached is turned—until it is approximately
level; then the slow motion screw is used for a final
adjustment to centre the bubble.
To measure the angle between two surfaces, the
clinometer is placed on each surface in turn and the
difference in angle can be calculated.
and the single ones from a point diametrically opposite ;
by using the double lines as an index for the single line,
any residual centring error of the circle is cancelled out.
The scales are illuminated by an intergrallow voltage
lamp.
The bubble unit is daylight illuminated, but is also
provided with a lamp for alternative illumination.
A locating face on the back allows the instrument to be
used horizontally with the accessory worktable or
reflector unit.
The reference for inclination is the bubble vial. In order to
measure the inclination of a surface, the vial—to which
the circle is attached is turned—until it is approximately
level; then the slow motion screw is used for a final
adjustment to centre the bubble.
To measure the angle between two surfaces, the
clinometer is placed on each surface in turn and the
difference in angle can be calculated.
The clinometer can be used as a precision setting
tool to set a tool head or table at a specific angle.
First the micrometerscale is set and then the glass
scale is rotated to bring the relevant graduation to
the index, using the slow motion screw for final
adjustment.
This sets the clinometer for the required angle.
Then the work surface it tilted until the bubble is
exactly centred.
The work surface is thus set to the specified angle
relative to a level plane.
tool to set a tool head or table at a specific angle.
First the micrometerscale is set and then the glass
scale is rotated to bring the relevant graduation to
the index, using the slow motion screw for final
adjustment.
This sets the clinometer for the required angle.
Then the work surface it tilted until the bubble is
exactly centred.
The work surface is thus set to the specified angle
relative to a level plane.
Angle Alignment Telescope:
Itisanimportantandpowerfulopticalinstrumenttocheckand
ensuregeometricalintegrityofcomponentsandassembly.
Theyhavetheadvantageofsimplicity,non-contact
measurements,versatilityandcosteffectiveness.
Itisaportableinstrumentandrequiressimplypowersupplyand
thuscanbeconvenientlyusedatsiteandineveryareaofthe
workshop/factory.
Theyareusedtomeasuredeviationinstraightness,check
alignment,squareness,flatness,parallelism,verticalityand
level.
Theyarealsousedforachievingprecisealignmentsettingson
largeengineeringcomponentsandstructuressuchasaircraft,
shipbuilding,missiles,cranes,satellitesystems,printing
presses,dieselengines,nuclearreactorsandrollingmills.
ensuregeometricalintegrityofcomponentsandassembly.
Theyhavetheadvantageofsimplicity,non-contact
measurements,versatilityandcosteffectiveness.
Itisaportableinstrumentandrequiressimplypowersupplyand
thuscanbeconvenientlyusedatsiteandineveryareaofthe
workshop/factory.
Theyareusedtomeasuredeviationinstraightness,check
alignment,squareness,flatness,parallelism,verticalityand
level.
Theyarealsousedforachievingprecisealignmentsettingson
largeengineeringcomponentsandstructuressuchasaircraft,
shipbuilding,missiles,cranes,satellitesystems,printing
presses,dieselengines,nuclearreactorsandrollingmills.
Theabilitytomovethefocusinglenseswithfreedomfrom
transversemovementortiltsisacriticalelementofthe
telescopedesign,determiningtheaccuracyoftheresultant
lineofsight.
Horizontalandverticaldisplacementfromatruelineof
sightaremeasuredviaatwo-axistiltingplatemicrometer
coupledtograduateddrums.
Themicro-alignmenttelescopeispresentlyavailableto
readdirectlytoµmandisabletofocusdowntozero
distancefromthefrontobjective.
Theprimaryopticalaxisisconcentricwithandparallelto
theoutsideofthetubetowithin6.4µmand3secondsof
arcrespectively.
Thetubeitselfiscylindricaltowithin5µm.
transversemovementortiltsisacriticalelementofthe
telescopedesign,determiningtheaccuracyoftheresultant
lineofsight.
Horizontalandverticaldisplacementfromatruelineof
sightaremeasuredviaatwo-axistiltingplatemicrometer
coupledtograduateddrums.
Themicro-alignmenttelescopeispresentlyavailableto
readdirectlytoµmandisabletofocusdowntozero
distancefromthefrontobjective.
Theprimaryopticalaxisisconcentricwithandparallelto
theoutsideofthetubetowithin6.4µmand3secondsof
arcrespectively.
Thetubeitselfiscylindricaltowithin5µm.
Inpracticeonecanreadilyachieveasettingaccuracyof50
µmatadistanceof30metersandproportionallyforlonger
andshorterdistancesdownto3meters.
Thismicroalignmenttelescopegeneratesastraightlineof
sightwhichisthebasicreferenceforallmeasurements.
Aprismisusedtodeviatethestraightlinetogenerate
squarenessandarotatingprismgeneratesflatness.
Thetelescopeisspeciallydesignedtofacilitate
autoreflectionandautocollimationprovidingfor
squarenessandangularmeasurementusingreflection
targetsandpolygons.
MountingAccessories:
1.Targetsandtargetholdersincludemirrortargetsforauto-
reflectionandautocollimation.
µmatadistanceof30metersandproportionallyforlonger
andshorterdistancesdownto3meters.
Thismicroalignmenttelescopegeneratesastraightlineof
sightwhichisthebasicreferenceforallmeasurements.
Aprismisusedtodeviatethestraightlinetogenerate
squarenessandarotatingprismgeneratesflatness.
Thetelescopeisspeciallydesignedtofacilitate
autoreflectionandautocollimationprovidingfor
squarenessandangularmeasurementusingreflection
targetsandpolygons.
MountingAccessories:
1.Targetsandtargetholdersincludemirrortargetsforauto-
reflectionandautocollimation.
2.Sweepopticalsquareisusedtosweepoutareferenceplane
at90̊tothetelescopeaxis,fromwhicherrorsofflatness
canbemeasured.
3.Opticalsquaresareusedtodeviatethelineofsightthrough
90̊towithin1secondofarcandtochecksquarenessof
axes.Theyarealsousedforsettingoutrightangleslinesof
sightlikecheckingthatamachinecolumnissquaretothe
bed.
4.Sphericalmountsinconicalseatingsareusedextensively
todefineafixedpointthroughwhichthetelescopelineof
sightortargetalwayspassesirrespectiveoftilt.
5.Telescopelamphouseaccessoryorseparatecollimatorunit
isusedtoachieveangularsettingandmeasurementofa
datum.
at90̊tothetelescopeaxis,fromwhicherrorsofflatness
canbemeasured.
3.Opticalsquaresareusedtodeviatethelineofsightthrough
90̊towithin1secondofarcandtochecksquarenessof
axes.Theyarealsousedforsettingoutrightangleslinesof
sightlikecheckingthatamachinecolumnissquaretothe
bed.
4.Sphericalmountsinconicalseatingsareusedextensively
todefineafixedpointthroughwhichthetelescopelineof
sightortargetalwayspassesirrespectiveoftilt.
5.Telescopelamphouseaccessoryorseparatecollimatorunit
isusedtoachieveangularsettingandmeasurementofa
datum.
Applications of Angle Alignment Telescope:
1.Measurement and setting of bearing alignment.
2.Alignment and squareness of axles, spindles and bores.
3.Straightness, flatness and squareness of bedwaysand
slides.
4.Alignment of engines with shafting, gearboxes and
compressors.
5.Parallelism and squareness of rollers and conveyors.
6.Squareness and alignment of assembly jigs.
7.Alignment to foundation blocks.
1.Measurement and setting of bearing alignment.
2.Alignment and squareness of axles, spindles and bores.
3.Straightness, flatness and squareness of bedwaysand
slides.
4.Alignment of engines with shafting, gearboxes and
compressors.
5.Parallelism and squareness of rollers and conveyors.
6.Squareness and alignment of assembly jigs.
7.Alignment to foundation blocks.
Angle Dekkor:
It is also one type of autocollimator.
It contains a small illuminated scale in the focal plane of
the objective lens(collimating lens).
This scale in normal position is
outside the view of the microscope
eyepiece.
This illuminated scale is projected as
a parallel beam by the collimating
lens which after striking a reflector
below the instrument is refocused by
the lens in the field of view of the
eyepiece.
It is also one type of autocollimator.
It contains a small illuminated scale in the focal plane of
the objective lens(collimating lens).
This scale in normal position is
outside the view of the microscope
eyepiece.
This illuminated scale is projected as
a parallel beam by the collimating
lens which after striking a reflector
below the instrument is refocused by
the lens in the field of view of the
eyepiece.
Inthefieldofviewofmicroscope,thereisanotherdatumscale
fixedacrossthecenterofscreenandthereflectedimageofthe
illuminatedscaleisreceivedatrightangletothisfixedscale
andthetwoscales,inthispositionintersecteachother.
Thereadingontheilluminatedscalemeasuresangular
deviationsfromoneaxisat90̊totheopticalaxisandthe
readingonthefixeddatumscalemeasuresthedeviationabout
anaxismutuallyperpendiculartotheothertwo.
Inotherwords,changesinangularpositionofthereflector
intwoplanesareindicatedbychangesinthepointof
intersectionofthetwoscales.
Thewholeoftheopticalsystemisenclosedinatube
whichismountedonanadjustablebracket.
fixedacrossthecenterofscreenandthereflectedimageofthe
illuminatedscaleisreceivedatrightangletothisfixedscale
andthetwoscales,inthispositionintersecteachother.
Thereadingontheilluminatedscalemeasuresangular
deviationsfromoneaxisat90̊totheopticalaxisandthe
readingonthefixeddatumscalemeasuresthedeviationabout
anaxismutuallyperpendiculartotheothertwo.
Inotherwords,changesinangularpositionofthereflector
intwoplanesareindicatedbychangesinthepointof
intersectionofthetwoscales.
Thewholeoftheopticalsystemisenclosedinatube
whichismountedonanadjustablebracket.
Uses:
Measuring angle of a component
To obtain precise angular setting for machining operations
Checking the sloping angle of a V-Block
To measure the angle of a cone or taper gauge.
Measuring angle of a component
To obtain precise angular setting for machining operations
Checking the sloping angle of a V-Block
To measure the angle of a cone or taper gauge.
Gauges:
Exact theoretical size derived from design calculations is
called Basic size.
While manufacturing a component, it is impossible to
manufacture exactly to the basic size.
Hence tolerance is specified for a basic size.
Ex: If 30 mm is the basic size, and if ±0.01 is the
tolerance,
Upper Limit = 30 + 0.01 = 30.01mm
Lower Limit = 30 –0.01 = 29.99mm
Hence the actual size of the part manufactured must lie
between the upper limit and lower limit.
When the actual size of a component is within the upper
and lower limit, it is accepted or else it is rejected.
Exact theoretical size derived from design calculations is
called Basic size.
While manufacturing a component, it is impossible to
manufacture exactly to the basic size.
Hence tolerance is specified for a basic size.
Ex: If 30 mm is the basic size, and if ±0.01 is the
tolerance,
Upper Limit = 30 + 0.01 = 30.01mm
Lower Limit = 30 –0.01 = 29.99mm
Hence the actual size of the part manufactured must lie
between the upper limit and lower limit.
When the actual size of a component is within the upper
and lower limit, it is accepted or else it is rejected.
Gauges: They do not indicate the actual value of the
inspected part of the component. They are used to
determine whether the part is made within the specified
limit.
Types: They are mainly classified as:
According to their type:
a)Standard Gauges: Made as an exact copy of the opposed
part.
b)Limit Gauges: Made to the limits of the dimensions.
According to their purposes:
a)Workshop Gauges: To check the dimension after
manufacturing.
b)Inspection Gauges: To check the part before final
acceptance.
inspected part of the component. They are used to
determine whether the part is made within the specified
limit.
Types: They are mainly classified as:
According to their type:
a)Standard Gauges: Made as an exact copy of the opposed
part.
b)Limit Gauges: Made to the limits of the dimensions.
According to their purposes:
a)Workshop Gauges: To check the dimension after
manufacturing.
b)Inspection Gauges: To check the part before final
acceptance.
c) Purchase Inspection Gauges: To check the part of other
factory.
d) Reference or Master Gauges: To check the dimensions of
the Gauges.
According to the form of the tested surface:
a)Plug Gauges: For checking the dimensions of the holes.
b)Snap and Ring Gauges: For checking the dimensions of
the shaft.
According to their Design:
a)Single Limit and Double Limit Gauges
b)Single Ended and Double Ended Gauges
c)Fixed and Adjustable Gauges
factory.
d) Reference or Master Gauges: To check the dimensions of
the Gauges.
According to the form of the tested surface:
a)Plug Gauges: For checking the dimensions of the holes.
b)Snap and Ring Gauges: For checking the dimensions of
the shaft.
According to their Design:
a)Single Limit and Double Limit Gauges
b)Single Ended and Double Ended Gauges
c)Fixed and Adjustable Gauges
Limit Gauges:
Limitgaugesaremadetothelimitsofthedimensionsof
theparttobetested.Therearetwolimitofdimensions,so
weneedtwolimitgauges.Theyare:
‘GOGauge’whichshouldpassthroughoroverapart.
‘NOGOGauge’whichshouldnotpassthroughorover
thepart.
Limitgaugesaremadetothelimitsofthedimensionsof
theparttobetested.Therearetwolimitofdimensions,so
weneedtwolimitgauges.Theyare:
‘GOGauge’whichshouldpassthroughoroverapart.
‘NOGOGauge’whichshouldnotpassthroughorover
thepart.
Plug Gauges:
UsedforGO/NO-GOassessmentofholeandslot
dimensionsorlocationscomparedtospecifiedtolerances.
Endsarehardenedandaccuratelyfinishedbygrinding.
OneendisGOendandtheotherendisNOGOend.
UsuallytheGOendwillbeequaltothelowerlimitsizeof
theholeandtheNOGOendwillbeequaltotheupper
limitsizeofthehole.
Ifthesizeoftheholeiswithinthelimits,thenGOend
shouldgoinsidetheholeandNOGOendshouldnotgo.
IftheGOenddoesnotgo,theholeisundersizeandalso
iftheNOGOendgoes,theholeisoversize.Hence,the
componentsarerejectedinboththecases.
dimensionsorlocationscomparedtospecifiedtolerances.
Endsarehardenedandaccuratelyfinishedbygrinding.
OneendisGOendandtheotherendisNOGOend.
UsuallytheGOendwillbeequaltothelowerlimitsizeof
theholeandtheNOGOendwillbeequaltotheupper
limitsizeofthehole.
Ifthesizeoftheholeiswithinthelimits,thenGOend
shouldgoinsidetheholeandNOGOendshouldnotgo.
IftheGOenddoesnotgo,theholeisundersizeandalso
iftheNOGOendgoes,theholeisoversize.Hence,the
componentsarerejectedinboththecases.
Types:
a)Double ended Plug gauges or wire gauges:In this type,
the GO end and NOGO end are arranged on both the
ends of the plug. This type has the advantage of easy
handling.
b)Progressive type Plug gauges or Stepped plug gauge: In
this type, both GO end and NOGO end are arranged in
the same side of the plug. Usually GO end is longer than
the NOGO end.
a)Double ended Plug gauges or wire gauges:In this type,
the GO end and NOGO end are arranged on both the
ends of the plug. This type has the advantage of easy
handling.
b)Progressive type Plug gauges or Stepped plug gauge: In
this type, both GO end and NOGO end are arranged in
the same side of the plug. Usually GO end is longer than
the NOGO end.
Ring Gauges:
Theyaremainlyusedtocheckthediameterofshafts
havingacentralhole.
Holeisaccuratelyfinishedbygrindingandlappingafter
hardeningprocess.
Theperipheryoftheringgaugesareusuallyknurledto
providegripwhilehandlingthem.
Wehavetomaketworinggaugesseparatelytocheckthe
shaftsuchasGOringgaugeandNOGOringgauge.
HereholeoftheGOringismadetotheupperlimitsizeof
theshaft.
HoleoftheNOGOringgaugeismadetolowerlimitsize
oftheshaft.
Theyaremainlyusedtocheckthediameterofshafts
havingacentralhole.
Holeisaccuratelyfinishedbygrindingandlappingafter
hardeningprocess.
Theperipheryoftheringgaugesareusuallyknurledto
providegripwhilehandlingthem.
Wehavetomaketworinggaugesseparatelytocheckthe
shaftsuchasGOringgaugeandNOGOringgauge.
HereholeoftheGOringismadetotheupperlimitsizeof
theshaft.
HoleoftheNOGOringgaugeismadetolowerlimitsize
oftheshaft.
TheNOGOringgaugeisidentifiedbyagroovecutonits
peripheryoraredmarkonit.
peripheryoraredmarkonit.
Snap Gauges/Gap Gauges:
Used to check external dimensions such as diameter or
thickness measurement.
They are similar to micrometer, Vernier, etc.,
They are available in fixed and variable forms.
Used to check external dimensions such as diameter or
thickness measurement.
They are similar to micrometer, Vernier, etc.,
They are available in fixed and variable forms.
Types:
a)Double ended Snap Gauges:
Have two ends in the form of anvils.
Here GO anvil is made to lower limit and NOGO anvil is
made to upper limit of shaft.
Also known as Solid Snap Gauges.
a)Double ended Snap Gauges:
Have two ends in the form of anvils.
Here GO anvil is made to lower limit and NOGO anvil is
made to upper limit of shaft.
Also known as Solid Snap Gauges.
b) Progressive Snap Gauges:
Also called Caliper Gauge.
Mainly used for checking large diameters upto100mm.
Both GO and NOGO anvils are at the same side.
GO anvil should be at the front and NOGO anvil at the
rear.
This type is made of horse shoe shaped frame with I
section to reduce the weight.
Also called Caliper Gauge.
Mainly used for checking large diameters upto100mm.
Both GO and NOGO anvils are at the same side.
GO anvil should be at the front and NOGO anvil at the
rear.
This type is made of horse shoe shaped frame with I
section to reduce the weight.
c) Adjustable Snap Gauge:
1.Usedforcheckinglargesizeshaftsmadewithhorse
shoeshapedframeof‘I’section.
2.Hasonefixedanvilandtwosmalladjustableanvils.
3.Thedistancebetweenthetwoanvilsisadjustedby
adjustingtheadjustableanvilsbymeansofsetscrews.
4.Adjustmentcanbemadewiththehelpofslipgaugesfor
specifiedlimitsofsize.
1.Usedforcheckinglargesizeshaftsmadewithhorse
shoeshapedframeof‘I’section.
2.Hasonefixedanvilandtwosmalladjustableanvils.
3.Thedistancebetweenthetwoanvilsisadjustedby
adjustingtheadjustableanvilsbymeansofsetscrews.
4.Adjustmentcanbemadewiththehelpofslipgaugesfor
specifiedlimitsofsize.
d) Plate type double ended Snap Gauges:
1.Used for sizes from 2mm to 100mm.
e) Plate type single ended Progressive Snap Gauges:
1.Used for sizes from 100mm to 250 mm.
1.Used for sizes from 2mm to 100mm.
e) Plate type single ended Progressive Snap Gauges:
1.Used for sizes from 100mm to 250 mm.
Taper plug Gauges:
Taper plug gauges are used to check tapered holes.
It has two check lines.
One is a GO line and another is a NOGO line.
During the checking of work, NOGO line remains outside
the hole and GO line remains inside the hole.
There are various types of taper plug gauges available:
1. Taper plug gauge -plain
2. Taper plug gauge -tanged
3. Taper ring gauge -plain
4. Taper ring gauge -tanged
Taper plug gauges are used to check tapered holes.
It has two check lines.
One is a GO line and another is a NOGO line.
During the checking of work, NOGO line remains outside
the hole and GO line remains inside the hole.
There are various types of taper plug gauges available:
1. Taper plug gauge -plain
2. Taper plug gauge -tanged
3. Taper ring gauge -plain
4. Taper ring gauge -tanged
Applications of Limit gauges
Limitgaugesareusedformeasuringthedifferent
parameters.Accordingtothemeasurementofparameters
involved,thegaugesare
(i)Threadgauges
(ii) Form gauges
(iii) Screw pitch gauges
(iv) Radius and fillet gauges
(v) Feeler gauges
(vi) Plate gauge and Wire gauge
(vii) Indicating gauges, and
(viii) Air gauges
Limitgaugesareusedformeasuringthedifferent
parameters.Accordingtothemeasurementofparameters
involved,thegaugesare
(i)Threadgauges
(ii) Form gauges
(iii) Screw pitch gauges
(iv) Radius and fillet gauges
(v) Feeler gauges
(vi) Plate gauge and Wire gauge
(vii) Indicating gauges, and
(viii) Air gauges
Thread gauge
Threadsarecheckedwiththehelpofthreadsgauges.
Forcheckinginternalthreads,(nuts,bushes)plugthread
gaugesareused.
Similarly,ringthreadgaugesareusedforchecking
externalthreads(bolts,screws).
Threadsarecheckedwiththehelpofthreadsgauges.
Forcheckinginternalthreads,(nuts,bushes)plugthread
gaugesareused.
Similarly,ringthreadgaugesareusedforchecking
externalthreads(bolts,screws).
Form gauge
Form gauges may be used to check the contour of a profile
of a work piece.
Form gauges are nothing but template gauges made of
sheet steel.
A profile gauges may contain two outlines which indicate
the limits of a profile.
Form gauges may be used to check the contour of a profile
of a work piece.
Form gauges are nothing but template gauges made of
sheet steel.
A profile gauges may contain two outlines which indicate
the limits of a profile.
Screw pitch gauge
Screwpitchgaugesareusedtocheckthepitchofthe
threadimmediately.
Itisverymuchineverydaytoolusedtopickouta
requiredscrew.
Thenumberofflatbladeswithdifferentpitchesispivoted
inaholder.
Thepitchvalueismarkedoneachblade.
Screwpitchgaugesareusedtocheckthepitchofthe
threadimmediately.
Itisverymuchineverydaytoolusedtopickouta
requiredscrew.
Thenumberofflatbladeswithdifferentpitchesispivoted
inaholder.
Thepitchvalueismarkedoneachblade.
Radius and Fillet gauge
Theradiusofcurvaturecanbemeasuredbyusingthese
gauges.
Theradiusmaybeeitherouterorinnerradius.
Accordingtothetypeofradiustobemeasured,theendof
thebladeismadetoeitherconcaveorconvexprofile.
Forcheckingouterradius,theprofileismadetoashapeof
concaveandconvexforinnerradius.
Theradiusofcurvaturecanbemeasuredbyusingthese
gauges.
Theradiusmaybeeitherouterorinnerradius.
Accordingtothetypeofradiustobemeasured,theendof
thebladeismadetoeitherconcaveorconvexprofile.
Forcheckingouterradius,theprofileismadetoashapeof
concaveandconvexforinnerradius.
Feeler gauge
Feelergaugesareusedforcheckingtheclearancebetween
matingsurfaces.
Theyaremainlyusedinadjustingthevalveclearancein
automobiles.
Theyaremadefrom0.03to1.0mmthickof100mmlong.
Thebladesarepivotedinaholder.
Feelergaugesareusedforcheckingtheclearancebetween
matingsurfaces.
Theyaremainlyusedinadjustingthevalveclearancein
automobiles.
Theyaremadefrom0.03to1.0mmthickof100mmlong.
Thebladesarepivotedinaholder.
Plate gauge and wire gauge
The thickness of sheet metal is checked by means of plate
gauges and wire diameters by means of wire gauges.
The plate gauge is made from 0.25 to 5.0mm and the wire
gauge from 0.1 to 10mm.
The thickness of sheet metal is checked by means of plate
gauges and wire diameters by means of wire gauges.
The plate gauge is made from 0.25 to 5.0mm and the wire
gauge from 0.1 to 10mm.
Indicating gauge
Theyaremainlydesignedformeasuringerrorsin
geometricalformandsize,andfortestingsurfaces
fortheirtruepositionwithrespecttooneanother.
Itcanbeusedforcheckingtherunoutoftoothed
wheel,pulleys,spindlesandvariousotherrevolving
partsofmachines.
Itcanbeeitheradialorlevertype.
Butdialtypesofindicatinggaugesarewidelyused.
Theyaremainlydesignedformeasuringerrorsin
geometricalformandsize,andfortestingsurfaces
fortheirtruepositionwithrespecttooneanother.
Itcanbeusedforcheckingtherunoutoftoothed
wheel,pulleys,spindlesandvariousotherrevolving
partsofmachines.
Itcanbeeitheradialorlevertype.
Butdialtypesofindicatinggaugesarewidelyused.
Air Gauges
Airgaugesareusedprimarilyfordeterminingtheinside
characteristicsofaholebymeansofcompressedair.
Therearetwotypesofairgauges.Theyareflow-typeand
pressure-typegauge.
Intheflow-type,theprincipleofvaryingairvelocitiesat
constantpressureandtheprincipleofairescapingthrough
onorificearesameasthatofthepressuretype.
Airgaugesareusedprimarilyfordeterminingtheinside
characteristicsofaholebymeansofcompressedair.
Therearetwotypesofairgauges.Theyareflow-typeand
pressure-typegauge.
Intheflow-type,theprincipleofvaryingairvelocitiesat
constantpressureandtheprincipleofairescapingthrough
onorificearesameasthatofthepressuretype.
Taylor’s Principle of Gauge Design:
Taylor’sprinciplestatesthatGOgaugeshouldcheckallthe
possibleelementsofdimensionsatatime(roundness,size,
location,etc.,)whereasNOGOgaugeshouldcheckonlyone
elementofthedimensionatatime.
TheotherstatementsofTaylor’sPrinciplearelisted:
1.GOgaugeshouldcheckthemaximummetalconditionand
NOGOgaugeshouldchecktheminimummetalcondition.
2.Asfaraspossible,theGOgaugeshouldassumethe
geometricalshapeofthecomponent.
3.Forcircularholes,theGOgaugeshouldbeapluggaugeand
theNOGOgaugeshouldbeapingauge.
4.Forcircularshafts,theGOgaugeshouldbearinggaugeand
theNOGOgaugeshouldbeasnapgauge.
Taylor’sprinciplestatesthatGOgaugeshouldcheckallthe
possibleelementsofdimensionsatatime(roundness,size,
location,etc.,)whereasNOGOgaugeshouldcheckonlyone
elementofthedimensionatatime.
TheotherstatementsofTaylor’sPrinciplearelisted:
1.GOgaugeshouldcheckthemaximummetalconditionand
NOGOgaugeshouldchecktheminimummetalcondition.
2.Asfaraspossible,theGOgaugeshouldassumethe
geometricalshapeofthecomponent.
3.Forcircularholes,theGOgaugeshouldbeapluggaugeand
theNOGOgaugeshouldbeapingauge.
4.Forcircularshafts,theGOgaugeshouldbearinggaugeand
theNOGOgaugeshouldbeasnapgauge.
Maximum Metal Condition:It refers to the condition of
hole or shaft when maximum material is left on. i.e., high
limit of shaft and low limit of hole.
Minimum Metal Condition: It refers to the condition of
hole or shaft when minimum material is left on such as
low limit of shaft and high limit of hole.
Plug Gauge Snap Gauge
hole or shaft when maximum material is left on. i.e., high
limit of shaft and low limit of hole.
Minimum Metal Condition: It refers to the condition of
hole or shaft when minimum material is left on such as
low limit of shaft and high limit of hole.
Plug Gauge Snap Gauge
GaugeTolerance:Theyaremanufacturedbysome
processes,whichrequiremanufacturingtolerance.After
knowingthemaximumandminimummetalconditionsof
thejobdimensionsunderinspection,thesizeofthegauge
toleranceonthegaugeisallowed.Thistolerance,to
anticipatetheimperfectionintheworkmanshipofthe
gauge-makeriscalledgaugemaker’stolerance.
Technicallytheyshouldbeassmallaspossible.
Limitgaugesareusuallyprovidedwiththegauge
toleranceof1/10
th
ofworktolerance.
Tolerancesoninspectiongaugesaregenerally5%ofthe
worktoleranceandthatonareferenceormastergaugeis
generally10%ofthegaugetolerance.
processes,whichrequiremanufacturingtolerance.After
knowingthemaximumandminimummetalconditionsof
thejobdimensionsunderinspection,thesizeofthegauge
toleranceonthegaugeisallowed.Thistolerance,to
anticipatetheimperfectionintheworkmanshipofthe
gauge-makeriscalledgaugemaker’stolerance.
Technicallytheyshouldbeassmallaspossible.
Limitgaugesareusuallyprovidedwiththegauge
toleranceof1/10
th
ofworktolerance.
Tolerancesoninspectiongaugesaregenerally5%ofthe
worktoleranceandthatonareferenceormastergaugeis
generally10%ofthegaugetolerance.
WearAllowance:Assoonasthegaugeisputintoservice,its
measuringsurfacerubsconstantlyagainstthesurfaceofthe
workpiece.Thisresultsintowearingofthemeasuringsurfaces
ofthegauge.Hence,itlosesitinitialdimensions.
Forthereasonofgaugeeconomy,itiscustomarytoprovidea
certainamountofwearallowancewhiledimensioningthe
gauge.
ItisprovidedforaGOgaugeandnotneededforNOGO
gauge.
Wearallowanceisusuallytakenas10%ofgaugetolerance.
Whenworktoleranceislessthan0.09mm,thereisnoneedof
givingallowanceforwear.
Ifworktoleranceismorethan0.09mm,then10%gauge
toleranceisgivenonlyon‘Go’gaugeforwear.
measuringsurfacerubsconstantlyagainstthesurfaceofthe
workpiece.Thisresultsintowearingofthemeasuringsurfaces
ofthegauge.Hence,itlosesitinitialdimensions.
Forthereasonofgaugeeconomy,itiscustomarytoprovidea
certainamountofwearallowancewhiledimensioningthe
gauge.
ItisprovidedforaGOgaugeandnotneededforNOGO
gauge.
Wearallowanceisusuallytakenas10%ofgaugetolerance.
Whenworktoleranceislessthan0.09mm,thereisnoneedof
givingallowanceforwear.
Ifworktoleranceismorethan0.09mm,then10%gauge
toleranceisgivenonlyon‘Go’gaugeforwear.
Problem:
Concept of Interchangeability:
Aninterchangeablepartisonewhichcanbesubstituted
forsimilarpartmanufacturedtothesamedrawing.
Whenonecomponentassemblesproperly(andwhich
satisfiesthefunctionalityaspectoftheassembly)withany
matingcomponent,bothchosenatrandom,thenitis
knownasinterchangeability.
Or
Thepartsmanufacturedundersimilarconditionsbyany
companyorindustryatanycorneroftheworldcanbe
interchangeable
Aninterchangeablepartisonewhichcanbesubstituted
forsimilarpartmanufacturedtothesamedrawing.
Whenonecomponentassemblesproperly(andwhich
satisfiesthefunctionalityaspectoftheassembly)withany
matingcomponent,bothchosenatrandom,thenitis
knownasinterchangeability.
Or
Thepartsmanufacturedundersimilarconditionsbyany
companyorindustryatanycorneroftheworldcanbe
interchangeable
Before the 18th century production used to be confined to
small number of units and the same operator could adjust the
mating components to obtain desired fit.
Devices such as guns were made one at a time by gunsmith.
If single component of a firearm needed a replacement, the
entire firearm either had to be sent to an expert gunsmith for
custom repairs, or discarded and replaced by another firearm.
HistoricalBackground
small number of units and the same operator could adjust the
mating components to obtain desired fit.
Devices such as guns were made one at a time by gunsmith.
If single component of a firearm needed a replacement, the
entire firearm either had to be sent to an expert gunsmith for
custom repairs, or discarded and replaced by another firearm.
HistoricalBackground
Eli Whitney and an early attempt
Eli Whitneyunderstood that developing "interchangeable
parts" for the firearms of the United Statesmilitary is
important.
In July 1801 he built ten guns, all containing the same
exact parts and mechanisms, then disassembled them
before the United States congress. He placed the parts in a
mixed pile and, with help, reassembled all of the firearms
right in front of Congress.
Eli Whitneyunderstood that developing "interchangeable
parts" for the firearms of the United Statesmilitary is
important.
In July 1801 he built ten guns, all containing the same
exact parts and mechanisms, then disassembled them
before the United States congress. He placed the parts in a
mixed pile and, with help, reassembled all of the firearms
right in front of Congress.
Interchangeabilityofpartsareachievedbycombininga
numberofinnovationsandimprovementsinmachining
operationssothatwewillableproducecomponentswith
accuracy.
Modernmachinetoolslikenumericalcontrol(NC)which
evolvedintoCNC.Jigsandfixtures.
Gaugestochecktheaccuracyofthefinishedparts.These
helpsinmanufacturingthecomponentswithinitsspecified
limits.
7/27/2017Interchangeability and Selective assembly151
numberofinnovationsandimprovementsinmachining
operationssothatwewillableproducecomponentswith
accuracy.
Modernmachinetoolslikenumericalcontrol(NC)which
evolvedintoCNC.Jigsandfixtures.
Gaugestochecktheaccuracyofthefinishedparts.These
helpsinmanufacturingthecomponentswithinitsspecified
limits.
7/27/2017Interchangeability and Selective assembly151
Ifaplotisdrawnoftheactualdimensionsofthe
similarcomponentsproducedbyawell-controlled
machine,itisfoundtofollowNormaldistribution.
σ=Standarddeviation
x̄=meanΣX/N,f=frequency
similarcomponentsproducedbyawell-controlled
machine,itisfoundtofollowNormaldistribution.
σ=Standarddeviation
x̄=meanΣX/N,f=frequency
Examplewehave100partseachwithaholeand100
shaftswhichhavetofitintotheseholes.
Ifwehaveinterchangeabilitythenwecanmakeanyone
ofthe100shaft&fititintoanyhole&besurethatthe
requiredfitcanbeobtained.
AnyM6boltwillfittoanyM6nutrandomlyselected.
Advantagesofinterchangeability:
1.Theassemblyofmatingpartsiseasier.Sinceany
componentpickedupfromitslotwillassemblewith
anyothermatingpartfromanotherlotwithout
additionalfittingandmachining.
2.Itenhancestheproductionrate.
3.Itbringsdowntheassemblingcostdrastically.
7/27/2017Interchangeability and Selective
assembly
153
shaftswhichhavetofitintotheseholes.
Ifwehaveinterchangeabilitythenwecanmakeanyone
ofthe100shaft&fititintoanyhole&besurethatthe
requiredfitcanbeobtained.
AnyM6boltwillfittoanyM6nutrandomlyselected.
Advantagesofinterchangeability:
1.Theassemblyofmatingpartsiseasier.Sinceany
componentpickedupfromitslotwillassemblewith
anyothermatingpartfromanotherlotwithout
additionalfittingandmachining.
2.Itenhancestheproductionrate.
3.Itbringsdowntheassemblingcostdrastically.
7/27/2017Interchangeability and Selective
assembly
153
4.Repairingofexistingmachinesorproductsis
simplifiedbecausecomponentpartscanbeeasily
replaced.
5.Replacementofwornoutpartsiseasy.
6.Withoutinterchangeabilitymassproductionisnot
possible.
Examples:
1.Keys
2.Couplings
3.Pin Joints
4.Screwed Fasteners
5.Gears
6.Clutches
simplifiedbecausecomponentpartscanbeeasily
replaced.
5.Replacementofwornoutpartsiseasy.
6.Withoutinterchangeabilitymassproductionisnot
possible.
Examples:
1.Keys
2.Couplings
3.Pin Joints
4.Screwed Fasteners
5.Gears
6.Clutches
Selective assembly
Thediscussionsofarhasbeeninconnectionwithfull
interchangeabilityorrandomassemblyinwhichany
componentassembleswithanyothercomponent.
Oftenspecialcasesofaccuracyanduniformityarises
whichmightnotbesatisfiedbycertainofthefitsgiven
underafullyinterchangeablesystem.
Forexampleifapartatitslowlimitisassembledwiththe
matingpartahighlimit,thefitsoobtainedmaynotfully
satisfythefunctionalrequirementsoftheassembly.
Alsomachinecapabilitiesaresometimesnotcompatible
withtherequirementsofinterchangeableassembly.
Thediscussionsofarhasbeeninconnectionwithfull
interchangeabilityorrandomassemblyinwhichany
componentassembleswithanyothercomponent.
Oftenspecialcasesofaccuracyanduniformityarises
whichmightnotbesatisfiedbycertainofthefitsgiven
underafullyinterchangeablesystem.
Forexampleifapartatitslowlimitisassembledwiththe
matingpartahighlimit,thefitsoobtainedmaynotfully
satisfythefunctionalrequirementsoftheassembly.
Alsomachinecapabilitiesaresometimesnotcompatible
withtherequirementsofinterchangeableassembly.
Forselectiveassembly,componentsaremeasuredand
sortedintogroupsbydimension,priortotheassembly
process.Thisisdoneforbothmatingparts.
Considerabearingassembly
Holewith25
+0⋅02
−0⋅02
,Shaft25
−0⋅14
−0⋅10
Clearanceshouldbe
0.14mm
Randomlyifwetake25
−0⋅02
and25
−0⋅10
clearancewillbe
0.08mm
HoleandShaftpairingrespctivelywhichgives0.14mm
clearance
24.97and24.83,25.0and24.86,25.02and24.88
sortedintogroupsbydimension,priortotheassembly
process.Thisisdoneforbothmatingparts.
Considerabearingassembly
Holewith25
+0⋅02
−0⋅02
,Shaft25
−0⋅14
−0⋅10
Clearanceshouldbe
0.14mm
Randomlyifwetake25
−0⋅02
and25
−0⋅10
clearancewillbe
0.08mm
HoleandShaftpairingrespctivelywhichgives0.14mm
clearance
24.97and24.83,25.0and24.86,25.02and24.88
Ifextremelytight(narrow)tolerancerangesarerequired,
itmaynotpossiblewithmachiningoperations.Insuch
caseweuseselectiveassembly
PinandHolewithslidingfit.
Holewith2??????
+0⋅0
+0⋅01
,Pinwith2??????
−0⋅01
+0⋅0
Ifpinscomingwithoversize20.003neednotbescrap,
theycanbematedwithHoles20.013
Sameforcomponentswithundersized.
itmaynotpossiblewithmachiningoperations.Insuch
caseweuseselectiveassembly
PinandHolewithslidingfit.
Holewith2??????
+0⋅0
+0⋅01
,Pinwith2??????
−0⋅01
+0⋅0
Ifpinscomingwithoversize20.003neednotbescrap,
theycanbematedwithHoles20.013
Sameforcomponentswithundersized.
Process capability
Theminimumtolerancedcomponentswhichcanbe
producedonamachinewithmorethan99%of
acceptabilitycalledasprocesscapability
80
±0.1
680/1000accuracy.
80
±0.2
910/1000
80
±0.3
991/1000(99%)
80
±0.4
993/1000
80
±0.6
1000/1000(100%)
Theminimumtolerancedcomponentswhichcanbe
producedonamachinewithmorethan99%of
acceptabilitycalledasprocesscapability
80
±0.1
680/1000accuracy.
80
±0.2
910/1000
80
±0.3
991/1000(99%)
80
±0.4
993/1000
80
±0.6
1000/1000(100%)
Problem-1
ForClearanceFit
Hole=2??????
+0⋅0
+0⋅1
Shaft=2??????
−0⋅15
−0⋅05
Toleranceforboth=0.1mm
Maximumclearance=H.Lofhole-L.Lofshaft=20.1-(19.85)=0.25mm
Minimumclearance=L.Lofhole-H.Lofshaft=20.0-(19.95)=0.05mm
Processcapability=0.3
Numberofgroups=(processcapability)/Tolerance=0.3/0.1=3
LetthosegroupsbedenotedbyA,B,C
TypeHole (mm)Shaft (mm)
A 2??????
+0⋅0
+0⋅1
2??????
−0⋅15
−0⋅05
B 2??????
+0⋅1
+0⋅2
2??????
−0⋅05
+0⋅05
C 2??????
+0⋅2
+0⋅3
2??????
+0⋅05
+0⋅15
ForClearanceFit
Hole=2??????
+0⋅0
+0⋅1
Shaft=2??????
−0⋅15
−0⋅05
Toleranceforboth=0.1mm
Maximumclearance=H.Lofhole-L.Lofshaft=20.1-(19.85)=0.25mm
Minimumclearance=L.Lofhole-H.Lofshaft=20.0-(19.95)=0.05mm
Processcapability=0.3
Numberofgroups=(processcapability)/Tolerance=0.3/0.1=3
LetthosegroupsbedenotedbyA,B,C
TypeHole (mm)Shaft (mm)
A 2??????
+0⋅0
+0⋅1
2??????
−0⋅15
−0⋅05
B 2??????
+0⋅1
+0⋅2
2??????
−0⋅05
+0⋅05
C 2??????
+0⋅2
+0⋅3
2??????
+0⋅05
+0⋅15
Group C holes with, Group C shaft
Hole Tolerance =0.1mm
Shaft Tolerance =0.1mm
Type of fit required is clearance.
Maximum clearance = H.L of hole -L.L of shaft
= 20.3-20.05
= 0.25mm
Minimum clearance = L.L of hole -H.L of shaft
= 20.2-20.15
= 0.05mm
Hole Tolerance =0.1mm
Shaft Tolerance =0.1mm
Type of fit required is clearance.
Maximum clearance = H.L of hole -L.L of shaft
= 20.3-20.05
= 0.25mm
Minimum clearance = L.L of hole -H.L of shaft
= 20.2-20.15
= 0.05mm
Advantages
Thereisalargernumberofacceptablepartsasoriginal
tolerancesaregreater
Thisinturnallowsthemanufactureofcheaperpartsas
lesswillbeconsignedtothewastebin.
SelectiveAssemblyassuresbetterandmoreaccurate
assemblyofpartsbyinsuringclosertolerancesbetween
thematingparts.
Risethequalityandlowermanufacturingcostsby
avoidingtighttolerances.
Reducestherejectionrate(scraprate)
Thereisalargernumberofacceptablepartsasoriginal
tolerancesaregreater
Thisinturnallowsthemanufactureofcheaperpartsas
lesswillbeconsignedtothewastebin.
SelectiveAssemblyassuresbetterandmoreaccurate
assemblyofpartsbyinsuringclosertolerancesbetween
thematingparts.
Risethequalityandlowermanufacturingcostsby
avoidingtighttolerances.
Reducestherejectionrate(scraprate)
Limitations
Duringusageoftheassemblyifonecomponentfails,first
weneedmanualofassemblyandidentifythegroupto
whichfailurecomponentbelongstoandsearchthe
componentinspareparts.
Byfocusingonthefitbetweenmatingparts,ratherthan
theabsolutesizeofeachcomponentsotherewillsmall
deviationinsizeofcomponent.
Duringusageoftheassemblyifonecomponentfails,first
weneedmanualofassemblyandidentifythegroupto
whichfailurecomponentbelongstoandsearchthe
componentinspareparts.
Byfocusingonthefitbetweenmatingparts,ratherthan
theabsolutesizeofeachcomponentsotherewillsmall
deviationinsizeofcomponent.
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