438387577-Presentation-on-Micrometer.pptx

micrometer

1. PRESENTATION ON :- MICROMETER

2. CONTENTS :- INTRODUCTION HISTORY PARTS OF MICROMETER TYPES OF MICROMETER PRINCIPLE OF MICROMETER HOW TO USE AND READ THE MICROMETER APPLICATION OF MICROMETER

3. INTRODUCTION :- A micrometer is a precision measuring instrument, used to obtain very fine measurements and available in metric and imperial versions . Metric micrometers typically measure in 0.01mm increments and imperial versions in 0.001 inches.  The measurements they provide can be more accurate than those given by other measuring devices such as dial calipers or vernier calipers, but depend very much on the user's care.   They are widely used in mechanical engineering for precisely measuring components.  Micrometers have two scales: a primary scale, on the barrel or sleeve, and a secondary scale, on the thimble .   Values are taken from each of these scales and combined to make the total measurement.        

4. A micrometer uses a calibrated screw or thread (found internally on the spindle) for measurement. Every time the spindle makes a complete revolution, the space between the measuring faces of the instrument (the spindle and the anvil) is adjusted by 0.5mm for metric versions and by 0.025 inch for imperial micrometers.  These are the smallest values that can be represented on the primary sleeve scale.  Although micrometers are highly accurate measuring devices, they are limited in their range. Micrometers typically have a measuring range of 25mm and 1 inch. For instance, metric versions measure 0-25mm, 25-50mm, 50-75mm etc, and imperial versions measure 0-1 inches, 1-2 inches, 2-3 inches etc.

5. HISTORY :- The word  micrometer  is a  neoclassical coinage  from Greek  micros , meaning 'small', and  metron , meaning 'measure '. The first ever micrometric screw was invented by William Gascoigne in the 17th century, as an enhancement of the  vernier ; it was used in a telescope to measure angular distances between stars and the relative sizes of celestial objects. Henry Maudslay  built a bench micrometer in the early 19th century that was jocularly nicknamed "the Lord Chancellor" among his staff because it was the final judge on measurement accuracy and precision in the firm's work. In 1844, details of Whitworth's workshop micrometer were published.This was described as having a strong frame of cast iron, the opposite ends of which were two highly finished steel cylinders, which traversed longitudinally by action of screws. The ends of the cylinders where they met was of hemispherical shape. One screw was fitted with a.

6. wheel graduated to measure to the ten thousandth of an inch. His object was  to furnish ordinary mechanics with an instrument which, while it afforded very accurate indications, was yet not very liable to be deranged by the rough handling of the workshop . The first documented development of handheld micrometer screw  calipers was by Jean Laurent Palmer of Paris in 1848 ;  the device is therefore often called  palmer  in French,  tornilol de Palmer  ("Palmer screw") in Spanish, and  calibro Palmer  ("Palmer caliper") in Italian. (Those languages also use the  micrometer  cognates:  micromètre The micrometer caliper was introduced to the mass market in anglophone countries by Brown & Sharpe in 1867 ,  allowing the penetration of the instrument's use into the average machine shop. Brown & Sharpe were inspired by several earlier devices, one of them being Palmer's design. In 1888, Edward W. Morley added to the precision of micrometric measurements and proved their accuracy in a complex series of experiments

7. PARTS OF MICROMETER :-

8. Micrometer measuring faces   Objects to be measured are placed between the measuring faces; the anvil and the spindle.   The anvil is the stationary measuring face against which parts are held until the spindle makes contact with the work.  The threaded spindle is the moving measuring face of the micrometer.    Micrometer sleeve scale    The scale on the sleeve of the micrometer is the instrument's primary measuring scale.  Together with the thimble scale, the sleeve scale displays the measurement taken.    The first significant figure of a measurement is taken from this scale. This part of the measurement is the first value immediately to the left of the thimble.      

9.   Micrometer thimble scale The secondary measuring scale, the thimble scale, provides the two remaining significant figures of a measurement.   This part of the measurement is the value on the scale that aligns with the index line on the sleeve scale.  Micrometer index line   The index line, which runs along the sleeve of the micrometer, is used to indicate the value shown on the thimble scale.    Micrometer thimble   When the thimble is turned, the spindle rotates and alters the distance between the measuring faces of the micrometer.   Some micrometer thimbles incorporate a friction drive. This allows for a more accurate reading particularly when used by the inexperienced user.

10.   Micrometer ratchet speeder  The ratchet speeder increases the speed at which the spindle rotates, so the space between the anvil and the spindle is reduced more quickly than it would be if the thimble were used.   Using the ratchet speeder reduces the time it takes to use the micrometer.   The ratchet incorporates a slipping clutch mechanism that prevents over tightening and aids the user to apply a constant measuring force to the spindle, helping to ensure reliable measurements.           Micrometer locking device   The locking device secures the spindle and preserves the measurement so that the micrometer can be removed from the workpiece before taking the reading.  Some micrometers have a lock nut , whilst others may have a locking lever

11. TYPES OF MICROMETER :-

12. Outside micrometer   The outside micrometer is the most commonly used type of micrometer . It is used to measure external dimensions such as the outside diameter of an object.

13.    Inside micrometer Inside micrometers are used to measure inside dimensions like the inside diameter of a hole or tube. There are two types of inside micrometer: caliper-type inside micrometers and tubular and rod inside micrometers.    

14. Depth Micrometer   Depth micrometers are used to measure the depths of holes, slots and steps.  They come with a variety of interchangeable rods of different lengths so that they can be used to measure a range of depths. 

15. PRINCIPLE OF MICROMETER:- The amount of rotation of an accurately made screw can be directly and precisely correlated to a certain amount of axial movement (and vice versa), through the constant known as the screw's  lead   . A screw's  lead  is the distance it moves forward axially with one complete turn (360 ° ). (In most threads [that is, in all single-start threads],  lead  and  pitch  refer to essentially the same concept.) With an appropriate lead and major diameter of the screw, a given amount of axial movement will be  amplified  in the resulting circumferential movement.

16. HOW TO USE AND READ THE MICROMETER :- Familiarize yourself with the anatomy of a micrometer Clean the anvil and spindle before beginning Hold the object in your left hand and place it against the anvil Hold the micrometer with your right hand.   Spin the ratchet counter clockwise.   Twist until the spindle is against the object Set the thimble lock while the micrometer is still on the object Slide out the object carefully.   Write down the measurements before unlocking the spindle

17. APPLICATION OF MICROMETER :-

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