Centre lathe
• 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.
A basic manual centre lathe
• The lathe is
controlled by a
person turning
handles on the
top slide and
cross slide in
order to make a
part.
Lathe Parts
• Lathe bed
 Made from rigid cast Iron
 Accurately machined
slideways
 Slideways guide carriage
& tailstock
 Headstock on upper end
of the lathe bed
Lathe parts
• Headstock
 Holds lathe spindle
and gears
 Chuck is fitted to
spindle
 Spindle is hollow for
long bars
Lathe parts
• Tailstock
 Can be moved along
slideways
 Can be clamped
in any location
 Inside tapered
to hold drill chuck
Lathe parts
• Carriage
 Moves along bed
between tailstock and
headstock
 Saddle – across the
lathe
 Apron – hangs down
in front
Lathe parts
• Cross Slide
 Fitted on the Saddle
 Moves cutting tool at
right angles to lathe
bed
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
Lathe parts
• Feed shaft
 Used to move the
Carriage
automatically
• Lead screw
 Used when screw
cutting on the lathe
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
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
Lathe parts
• Tool holders
 Used for holding
cutting tool bits
 Available in Right
hand, left hand and
straight
• Cutting Tools
 Can be High Speed
Steel held in tool
holders
 Can be also Ceramic
(Tungsten carbide)
bits held directly in
toolpost
Cutting Tool Angle
• Clearance angle
 Ensures only the
cutting edge of the
tool touches the work
 Too much clearance
causes chatter
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
Cutting tool angle
• Tool bits are held in
holders at an angle of
about 15°
Cutting tools
• We can put different shapes on the High
speed tool bits to cut different shapes on the
workpiece
Lathe operations
Facing off
Parallel Turning
Parallel Turning
Parallel Turning
• The tool moved parallel to
the work and cylindrical
shapes are
formed
• Also known as sliding
Parallel Turning
• The student can Parallel turn the work on the
lathe manually or use the automatic traverse
option
Facing off
• The tool is moved at
right angles to the
work using the cross
slide
• Flat surfaces are
produced
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
Knurling
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.
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
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.
CNC Lathes
• 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.
LATHE OPERATIONS
Producing a Flat Surface
Producing a
Cylindrical Surface
.
Taper Turning
Radius Turning Attachment
Drilling on a Lathe
Parting Off / Under Cutting
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Center lathe - Summerhill College