Centre lathe

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Centre lathe

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• 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.

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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.

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Lathe Parts

• Lathe bed
• Made from rigid cast Iron
• Accurately machined slideways
• Slideways guide carriage tailstock
• Headstock on upper end of the lathe bed

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Lathe parts

• Headstock
• Holds lathe spindle and gears
• Chuck is fitted to spindle
• Spindle is hollow for long bars

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Lathe parts

• Tailstock
• Can be moved along slideways
• Can be clamped
• in any location
• Inside tapered
• to hold drill chuck

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Lathe parts

• Carriage
• Moves along bed between tailstock and headstock
• Saddle across the lathe
• Apron hangs down in front

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Lathe parts

• Cross Slide
• Fitted on the Saddle
• Moves cutting tool at right angles to lathe bed

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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

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Lathe parts

• Feed shaft
• Used to move the Carriage automatically
• Lead screw
• Used when screw cutting on the lathe

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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

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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

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Lathe parts

• Tool holders
• Used for holding cutting tool bits
• Available in Right hand, left hand and straight

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

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Cutting Tool Angle

• Clearance angle
• Ensures only the cutting edge of the tool touches
  the work
• Too much clearance causes chatter

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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

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Cutting tool angle

• Tool bits are held in holders at an angle of
  about 15

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Cutting tools

• We can put different shapes on the High speed
  tool bits to cut different shapes on the workpiece

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Lathe operations

• Facing off
• Parallel Turning
• Parallel Turning

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Parallel Turning

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

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Parallel Turning

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

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Facing off

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

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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

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Knurling
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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.

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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

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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.

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CNC Lathes
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• 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.

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LATHE OPERATIONS    
Producing a Flat Surface
Producing a Cylindrical Surface
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Taper Turning
   
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Radius Turning Attachment
Drilling on a Lathe
Parting Off / Under Cutting