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 parte.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 Cylindrical Surface

Taper Turning

Producing a Flat Surface

Drilling on a Lathe

Parting Off / Under Cutting

Radius Turning Attachment