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The Centre lathe. Damian Keenan. 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.
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The Centre lathe Damian Keenan
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 • This type of lathe is controlled by a person turning the various handles on the top slide and cross slide in order to make a product / 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 of the Crossslide 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 • Turning • Facing off
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
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 lather must be set to the exact centre of the workpiece • We use the center 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.
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