Oriental University, Indore (M.P.)
Transcript of Oriental University, Indore (M.P.)
Oriental University, Indore (M.P.)
LATHE MACHINE
S N DUBEY Assistant Professor
Department of Mechanical Engineering
Centre 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
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
• 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
Tool Holders
Cutting Tool Materials• Carbon Steels
• High Speed Steel (HSS)
• Stellite
• Carbides
• Diamond
Carbon Steels• Carbon steels start to soften at a
temperature of about 180oC. This limitation means that such tools are rarely used for metal cutting operations. widely used for woodworking and they can be used in a router to machine aluminum sheet up to about 3mm thick.
High Speed Steel (HSS)
• HSS tools are so named because they were developed to cut at higher speeds. They are tough and suitable for interrupted cutting and are used to manufacture tools of complex shape such as drills, reamers, taps, dies and gear cutters. Tools may also be coated to improve wear resistance.
Stellite
• A non-ferrous alloy of chromium and cobalt, so hard that it cannot be forged or machined except by grinding, it is usually used in the form of a tipped tool.
Carbides
• Also known as cemented carbides or sintered carbides .Have high hardness over a wide range of temperatures and high thermal conductivity. Can be shaped only by special grinding wheels and is always used in the form of a tipped tool.
Diamond• The hardest known substance is diamond. It
is most suited for light uninterrupted finishing cuts at almost any speed and is mainly used for very high speed machining of aluminum - silicon alloys, composites and other non - metallic materials.
Tool Forms
• Solid ToolsMade throughout in one material. Normally
HSS or carbon
Butt-Brazed
• Tools made by brazing or welding a piece of HSS to a high tensile steel shank.
Tipped Tool
• Have a tip of cemented carbide, etc, brazed to a blank of high tensile steel.
Tool Bit and Holder
• Tool bits are held in holders at an angle of about 15°
• 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
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.
Boring
Boring Tools
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
Tool shape
• The shape of the tool and the angles of its ground faces will depends on:
The operation to be performedThe material which has to be machinedThe power & rigidity of the latheThe amount of material to be removedThe quality of finish desired.
Cutting tools
• We can put different shapes on the High speed tool bits to cut different shapes on the workpiece
Home work• Sketch and explain the following
1. Solid tools
2. Butt brazed
3. Tipped tools
Sketch and explain the following tool shape• Fine finishing• Round nose rougher
• Round nose• Internal screw cutting tool• Parting off tool• Knife tool• Form tool