Center_lathe.ppt chinhoyi university zimbabwe

notes

1. Centre lathe

3. •The Centre Lathe is used to manufacture cylindrical
shapes from a range of materials including; steels and
plastics.
•Components that assemble to make an car engine work
have been made using lathes.
•The Lathe may be operated by people (manual lathes)
or computer controlled lathes (CNC machines) that
have been programmed to carry out a particular task.

4. A basic manual centre lathe
•The lathe is
controlled by a
person turning
handles on the
top slideand
cross slidein
order to make a
part.

5. Lathe Parts
•Lathe bed
Made from rigid cast Iron
Accurately machined
slideways
Slidewaysguide carriage
& tailstock
Headstockon upper end
of the lathe bed

6. Lathe parts
•Headstock
Holds lathe spindle
and gears
Chuckis fitted to
spindle
Spindleis hollow for
long bars

7. Lathe parts
•Tailstock
Can be moved along
slideways
Can be clamped
in any location
Inside tapered
to hold drill chuck

8. Lathe parts
•Carriage
Moves along bed
between tailstockand
headstock
Saddle–across the
lathe
Apron–hangs down
in front

9. Lathe parts
•Cross Slide
Fitted on the Saddle
Moves cutting tool at
right angles to lathe
bed

10. Lathe parts
•Top Slide
(Compound slide)
Fitted to top of Cross slide
Carries toolpost and cutting
tool
Can rotate to any angle
Is used to turn tapers

11. Lathe parts
•Feed shaft
Used to move the
Carriage
automatically
•Lead screw
Used when screw
cutting on the lathe

12. Lathe Parts
•Three Jaw Chuck
Self centring
Holds round and
hexagonal work
3 jaws are connected
Jaws are stamped 1,2 & 3
and fitted in order
Chuck key used to open

13. Lathe parts
•Toolpost
Fitted on top slide and
carries the cutting tool
or the cutting tool
holder
Can adjust the height
on some types
Can carry 4 different
tool holders

14. Lathe parts
•Tool holders
Used for holding
cutting tool bits
Available in Right
hand, left hand and
straight

15. •Cutting Tools
Can be High Speed
Steel held in tool
holders
Can be also Ceramic
(Tungsten carbide)
bits held directly in
toolpost

16. Cutting Tool Angle
•Clearance angle
Ensures only the
cutting edge of the
tool touches the work
Too much clearance
causes chatter

17. Cutting tool angle
•Rake Angle
Allows the chip being cut
to flow out
Changing the rake
changes the power used in
cutting and the heat
generated
Large rake = soft ductile
materials
Small rake = hard brittle
materials

18. Cutting tool angle
•Tool bits are held in
holders at an angle of
about 15°

19. Cutting tools
•We can put different shapes on the High
speed tool bits to cut different shapes on the
workpiece

20. Lathe operations
Facing off
Parallel Turning
Parallel Turning

21. Parallel Turning
•The tool moved parallel to
the work and cylindrical
shapes are
formed
•Also known as sliding

22. Parallel Turning
•The student can Parallel turn the work on the
lathe manually or use the automatic traverse
option

23. Facing off
•The tool is moved at
right angles to the
work using the cross
slide
•Flat surfaces are
produced

24. Knurling
•A knurling tool is used to press a pattern onto a
round section.
•The pattern is normally used as a grip for a
handle.
•This provide a grip for the round part
e.g. Screwdriver

25. Knurling

26. Parting off
•If the student wants to cut
off the part they have
turned, they can use the
hacksaw and a vice or use
the parting off tool on the
lathe.

27. Setting the tool height
•The cutting tool on the
lathe must be set to the
exact centre of the
work-piece
•We use the centre of
the tailstock to guide
us to the correct height

28. Screw-cutting on the lathe
•Lathes are also used to
cut threads in round
bars
•These threads take up
different profiles e.g
iso (60°) ACME etc.
•These threads can be
seen on bench vices,
lathes etc.

29. CNC Lathes

30. •In Industry it is not
efficient or profitable to
make everyday products
by hand.
•On a CNC machine it is
possible to make hundreds
of the same item in a day.
•First a design is drawn
using design software,
then it is processed by the
computer and made using
the CNC machine.
•In industry, CNC
machines can be
extremely large.

31. LATHE OPERATIONS
.
Producing a
Cylindrical Surface
Taper Turning
Producing a Flat Surface

32. Drilling on a Lathe
Parting Off / Under Cutting
Radius Turning Attachment