Lathe Machine

INDUSTRIAL TRAINING INSTITUTE MAHESANA GUJARAT

CENTRE OF EXCELLANCE( MECHANICAL SECTOR )

BASIC TURNING AND GRINDING

INSTRUCTOR

SHRI.R.B.PATEL

DURATION

8 WEEKS

MODULE : 4

BASIC TURNING AND GRINDING

SPLIT-UP OF SYLLABUS(THEORY)

Week No.

Lesson No.

Name of the Lesson.

(Turning)

1. 1. Introduction of ITI & Manufacturing process.

2. Lathe machine – types – specification.

2. 3. Lathe Machine parts-Construction-Function.

4. Lathe Operations.

5. Work Holding devices and Accessories.

3. 6. Lathe Tools and their Angle.

7. Taper – Method – Uses – Calculation.

8. Thread – Types – uses – Calculation.

4. 9. Speeds , Feed & depth of cut of Lathe Machine.

10. Coolants - Types – Application.

Week No.

Lesson No.

Name of the Lesson.

(Grinding)

5. 11. Grinding – Principle – Process – Safety.

12. Grinding Wheels – Types – Selection.

6. 13. Grinding Wheels Mounting & Balancing – Grinding Wheels Dressing & Turning.

14. Surface Grinding Machine-Parts-Types-Uses

7. 15. Cylindrical Grinding Machine-Parts-Types-Uses.

16. Grinding Diffect and Remindes.

8. 17. Heat Treatment Process – Anealing – Normalizing – Case Hardening.

18. Steel – Classification – Alloings elements.

TYPES OF SAFETY

• General safety• Personal safety• Machine safety

• Wear a one piece overall or boiler suit.• Keep the over all buttons fastened.• Don’t use ties and scarves.• Cut the hair short. • Don’t wear a ring,watch or chain.

PERSONAL SAFETY

MACHINE SAFETY

• Switch off the machine immediately if something goes wrong.

• Keep the machine clean.• Stop the machine before changing the speed.• Check the oil level before starting the machine.

LATHE M/C INTRODUCTION & SPECIFICATION

• The length of bed.• The maximum diameter(swing)of the work that

can be turned.• The length between centers and the pitch of the

lead screw.

TYPES OF LATHES

• Speed lathes

• engine lathes

• Bench lathes

• Tool room lathes

• Capstan and turret lathes

• Special purpose lathes

• Automatic lathes

PARTS OF LATHE M/C

• Headstock • bed• Cross slide• Compound rest• Tail stock• Feed shaft• Carriage• Lead screw• Leg• Quick change gear box

HEAD STOCK

• All – Geared Headstock• Cone Pulley Drive Headstock

CARRAIGE

• Tool post• Cross – slide• Top slide• Saddle• Saddle lock• Compound rest• Apron

BED

• Vee slides• Heavily ribbed• Machined ways• Heavy construction fine grain cast iron

TAIL STOCK

• Base

• Body

• Spindle

• spindle locking lever

• Operating screw rod

• Operating nut

• Tailstock hand wheel

• Key

• Clamping unit

FEED MECHANISM

• Spindle gear• Tumbler gear unit• Fixed stud gear• Change gear unit• Quick change gearbox• Feed shaft/lead screw• Apron mechanism

TOOL POST

• American type tool post• Indexing type tool post• Quick change tool post

THREE JAW CHUCK

• Backplate• Body• Jaws• Crown wheel• Pinion

SPECIFICATION OF A CHUCK

• Type of chuck• Capacity of the chuck• Diameter of the body• Width of the body• Method of mounting to the spindle nose

FOUR JAW CHUCK

• Backplate• Body• Jaws• Square threaded screw shaft

DIFFERENCE BETWEEN 3 & 4 JAW CHUCK

• Setting up of work is easy

• Has less gripping power• Depth of cut is

comparatively less• Heavier jobs cannot be

turned• Workpieces cannot be

set for eccentric turning

• Setting up of work is difficult

• More gripping power• More depth of cut can

be given• Heavier jobs can be

turned• Workpieces can be set

for eccentric turning

TYPES OF LATHE CENTERS

• Ordinary centre • Half centre• Tipped centre• Ball centre• Pipe centre• Revolving centre• Insert type centre• Self-driving centre• Female centre• Swivel `v` centre

TYPE OF CARRIERS

• Straight tail carrier• Bent carrier• Clamp type carrier

DRIVING PLATE

• Catch plates• Driving plates• Safety driving plates

FACE PLATE

• Face-plates with only elongated radial slots• Face-plates with elongated slots and `T`slots• Face-plates with elongated radial slots and

additional parallel slots.

STEADY REST

• Fixed steady rest• Follower steady rest

FIXED STEADY REST

• Top portion

• Lock screw top portion

• Adjustable pads

• Work

• Hinge

• Bearing pads locking screw

• Base

• Lathe bed clamp

FOLLOWER STEADY REST

• Locking screw• Bearing pads• Adjusting screws• Frame

LATHE MACHINE OPERATION - FACING

• This is an operation of removing metal from the work-face by feeding the tool at right angles to the axis of the work.

PURPOSE OF FACING

• To have a reference plane to mark and measure the step lengths of work.

• To have a face at right angle to the axis of the work.

• To remove the rough surface on the faces of the work and have finished faces instead.

• To maintain the total length of the work.

PLAIN TURNING

• Rough turning, using roughing tool or knife tool.

• Finish turning using a finishing tool.

GROOVING

• Grooving is the process of turning a grooved form or channel on a cylindrically turned work piece. The shape of the cutting tool and depth to which it is fed determine the shape of the groove.

TYPE OF GROOVES

• Square grooves• Round groove• `V`shaped groove

CHAMFERING

• To remove burrs and sharp edges from the turned components to make their handling safe.

• To permit for easy assembly of mating components.

• To provide better appearance.

MATHOD OF CHEFERING

• Form tool method• Filling method• Compound slide method

TYPE OF KNURLING

• Diamond knurling• Straight knurling • Cross knurling• Concave knurling• Convex knurling

TYPES OF MANDRELS

• Expansion mandrel• Gang mandrel• Stepped mandrel• Screw or threaded mandrel• Taper shank mandrel• Cone mandrel

DRILLING AND BORING

• Drilling is the operation of originating circular holes. The tool employed for this purpose is a drill.

• Two different method are employed in a lathe for this operation.

• Work is clamped in the headstock in a chuck or on the faceplate. The drill is held in the tailstock and fed.

TAPER

• A Taper is uniform increase or decrease in diameter along the length of a cylinder.

TYPES OF TAPER

• Self-holding tapers• Quick releasing tapers• Morse taper• Brown and sharpe taper• Jarno taper• Metric taper• Pin taper

TAPER TURNING METHOD

• Form tool method• Compound slide method• Tailstock offset method• Taper turning method• Taper turning attachment method

SCREW THREAD

• A screw thread is a ridge of uniform section formed helically on the surface of a cylindrical body.

• An external screw thread is formed on the outer surface of a cylindrical part.

USE OF SCREW THREAD

• As fasteners to hold together and dismantle.components when needed

• To transmit motion on machine from one unit to another

• To make accurate measurements• To apply pressure

PART OF SCREW THREAD

• Crest• Root• Flank• Thread angle• Depth• Major diameter• Minor diameter• Pitch diameter• Lead• Helix angle

FORM OF SCREW THREAD

• Vee threads• Square threads• Trapezoidal threads

CUTTING TOOLS CLASSIFICATION

• Single point cutting tools• Multi point cutting tools• Form tools

TYPES OF LATHE CUTIING TOOL

• Solid type tools• Brazed type tools• Inserted bits with holders• Throw away type tools

CUTTTING TOOLS ANGLE

• Side cutting edge angle• End cutting edge angle• Top rake angle• Side rake angle• Front clearance angle• Side clearance angle

EFFECT TOOL SETTING AND TOOL ANGLES

• When tools are set above or below the centre line of the work piece, the clearance angles and rake angle will change.

CUTTING TOOL MATERIALS

• Ferrous tool materials • Non-ferrous tool materials• Carbides• Non-metallic materials

TYPE OF BORING TOOL

• Solid forged tools• Boring bars with inserted bits

CUTTING SPEED OF LATHE MCHINE

• The finished required• Depth of cut• Tool geometry• Properties and rigidity of the cutting tool and

its mounting• Properties of the workpiece material• Rigidity of the workpiece• The type of cutting fluid used• Rigidity of the machine tool

FEED

• Tool geometry• Surface finish required on work• Rigidity of the tool • Coolant used

CUTTING SPEEDS AND FEEDS FOR H.S.S TOOL

Material being turned Feed mm/rev Cutting speed m/min.

Aluminium 0.2-1.00 70/100

Brass (alpha)-ductile 0.2-1.00 50-80

Brass (free cutting) 0.2-1.5 70-100

Bronze (phosphor) 0.2-1.00 35-70

Cast iron (grey) 0.15-0.7 25-40

Copper 0.2-1.00 35-70

Steel (mild) 0.2-1.00 35-50

Steel (medium carbon) 0.15-0.7 30-35

Steel (alloy-high tensile) 0.08-0.3 5-10

Thermosetting plastics 0.2-1.00 35-50

CUTTTING FLUIDS

• Application of the cutting fluid is very important in a grinding operation. The cutting fluid should be applied in adequate quantity and at very low pressure. The cutting fluid should be directed on the work just above the point where it make contact with the wheel ie.contact zone.

ADVANTAGE OF CUTTING FLUIDS

• It removes the heat general.• It improves the surface finish of the workpiece.• It maintains the hardness of the heat-treated

works.• It removes burn marks on the ground surface.• It keeps the grinding wheel face clean.

IMPORTANT POINTS TO BE NOTED WHILE USING CUTTING FLUIDS

• Always add pure water to soluble oils.• Do not allow soluble oil to mix with other oils.• Always mix water to the oil in correct

proportion and not oil to the water.• It should be kept cool under normal

temperature.

INTRODUCTION TO GRINDING PROCESS

• It is the only economical method of cutting hard material like hardened steel.

• It produces very smooth surface up to N4, suitable for bearing surface.

• Surface pressure is minimum in grinding. It is suitable for light work,which will spring away from the cutting tool in the other machining processes.

GENERAL SAFETY

• Keep the floor and gangways clean and clear.• Don’t touch or handle any equipment/machine

unless authorized to do so.• Don’t walk under suspended .• Use the correct tools for the job.• Keep the tools at their proper palace.• Wipe out split oil immediately.• Ensure adequate light in the workshop.

CONSTRUCTION OF A GRINDING WHEEL

• In order make the grinding wheel suitable for different work situations,the features such as abrasive, grain size, grade, structure and bonding materials can be varied.

• A grinding wheel consists of an abrasive that does the cutting, and a bond that holds the abrasive particles together.

ABRASIVES

• There are two types of abrasives.• Natural abrasives• Artificial abrasives

GRAIN SIZE

• The number indicating the size of the grit represents the number of openings in the sieve used to size the grain. The larger the grit size number , the finer the grit.

GRADE

• Grade indicates the strength of the bond and, therefore, the `hardness` of the wheel. In a hard wheel the bond is strong and it securely anchor the grit in place, and therefore, reduces the rate of wear. In a soft wheel, the bond is weak and the grit is easily detached resulting in a high rate of wear.

STRUCTURE

• This indicates the amount of bond present between the individual abrasive grains, and the closeness of the individual grain to each other. An open structured wheel will cut more freely. That is, it will remove more metal. In a given time and produce less heat.

BOND

• Vitrified bond (V)• Silicate bond (S)• Shellac bond (E)• Rubber bond (R)• Resinoid bond (B)

STANDARD SHAPES OF GRINDING WHEELS

• Straight wheel• Cylinder• Tapered• Recessed one side• Straight cup• Recessed both sides• Flaring cup• Dish• Saucer• Mounted wheels

SPECIFICATION OF GRINDING WHEELS

• Standard wheel markings• Diameter of the wheel• Bore diameter of the wheel • Thickness of the wheel• Type of the wheel

SELECTION OF GRINDING WHEEL

For grinding a job the right grinding wheel is to be selected. The selection of a grinding wheel will depend on the following factors.

• Material to be ground• Amount of stock to be removed• Finish required • Area of contact• Wheel speed• Work speed• Personal factor• Method of cooling

GRINDING WHEEL DRESSING &TRUING

• Dressing refers to the removing of clogs and blunt abrasive grains from the surface of the grinding wheel. Dressing exposes the cutting edges which restore the correct cutting action of the wheel. Dressing is done on a glazed or loaded wheel to recondition it.

• Truing refers to the shaping of the wheel to make it run concentric with the axis. When a new grinding wheel is mounted, it must be trued before use to remove the run out.

GLAZING & LOADING

• When the surface of a grinding wheel develops a smooth and shining appearance, it is said to be glazed. This indicate the abrasive particles on the wheel face are not sharp. These are worked down to bond level.

• When soft materials like aluminium, copper, lead, etc. are ground the metal particles get clogged between the abrasive particles. This condition is called loading.

GRINDING SPEED

TYPE OF GRINDING

WHEEL SPEED m/sec.

Rough grinding wheel with vitrified bond 25

Rough grinding wheels with resinoid bond 45

Surface grinding wheels with vitrified bond 20-25

Internal grinding wheels with vitrified bond 20-35

Centreless grinding wheels with vitrified bond 30-80

Cylindrical grinding wheels with vitrified bond 30-35

Cutting off wheels with resinoid bond 45-80

Hand grinding of tools 20-25

Automatic grinding of tools 25-35

Hand grinding of carbide tools 18-25

WORK SPEED

CLASS OF WORK ROUGH GRIND m/min.

FINISH GRIND m/min.

Soft steel 10-20 20-25

Hardened steel 25-30 30-40

Cast iron 35-55 45-65

Aluminium and fine brass

50-65 50-65

DEPTH OF CUT

• It is the thickness of the material removed in surface grinding for one cut.

• Depth of cut in grinding depend on the:• Cutting load• Power of the machine• Finish required

SURFACE GRINDING MACHINE

• It is precision grinding machine to produce flat surface on a workpiece. It is a more economical and more practical method of accurately finishing flat surface than filling and scraping.

PRECISION SURFACE GRINDER

SPECIFICATION OF A SURFACE GRINDER

• Maximum dia. of the wheel that can be held on the spindle.

• Maximum size of the job that can be ground.(length*width*height)(150*150*400).

• The type of drive of the work table:hydraulic/electrical.

TYPES OF SURFACE GRINDERS

• Horizonal spindle reciprocating table• Horizontal spindle rotary table• Vertical spindle reciprocating table• Vertical spindle rotary table

HORIZONTAL TYPE GRINDER

• Base• Saddle• Table• Wheel head

WORK HOLDING DEVICES

The work holding devices used in grinding are:• Magnetic chuck• Vice• Angle plates• `V`blocks• clamps

MAGNETIC CHUCK

Magnetic chucks are of two types• Electromagnetic chuck• Permanent magnetic chuck

The magnetic power of the electro magnetic chuck can be varied according to the size of the work. But not so in the case of a permanent magnetic chuck.

TILTING TYPE VICE

• A tilting vice is used to hold the workpiece while grinding angular surfaces. If required the tilting base can be removed and it can be mounted on the magnetic chuck as a plain vice.

SURFACE GRINDING OPERATIONS

• Grinding flat surface • Grinding vertical surface • Grinding slot• Grinding angular surface• Grinding a radius• Cutting off

CYLINDRICAL GRINDERS

• Cylindrical grinders are used to grind the external of internal surface of a cylindrical workpiece. By cylindrical grinding the diameter of a workpiece can be maintained to a close tolerance (up to 0.0025 mm), and a high quality surface finish can be obtained (up to N4).

TYPES OF CYLINDRICAL GRINDERS

• External cylindrical grinders• Internal cylindrical grinders• Universal cylindrical grinders• Centreless grinders

GRINDING ALLOWANCE

• Machine parts are processed in different machine such as lathes, shaping machines, etc. in such a way that their final dimension have some stock left, which is finished during the grinding operation. The amount of this stock left is called the `grinding` allowance.

IMPORTANT FACTORE OF GRINDING ALLOWANCE

• Harness of material to be ground• Whether the part has to be heat – treated• Case depth of case hardened workpiece• Grint and grade of grinding wheel• Whether grinding is done wet or dry grinding

HEAT TREATMENT PURPOSE

• The properties of steel depend upon its composition and its structure. These properties can be changed to a considerable extent, by changing either its composition or its structure. The structure of steel can be changed by heating it to a particular temperature, and then, allowing it to cool at a definite rate. The process of changing the structure and thus changing the properties of steel, by heating and cooling, is called `heat treatment of steel`.

TYPES OF STRUCTURE OF STEEL

• The structure of steel become visible when a piece of the metals broken. The exact grain size and structure can be seen through a microscope. Steel is classified according to its structure.

HEAT TREATMENT PROCESS & PURPOSE

• Hardening :- To add cutting ability• Tempering :- To induce toughness and shock

resistance.• Annealing :- To relive toughness and stress.• Normalizing:- To refine the grain structure of

the steel.

• Steel is an alloy of iron and carbon. But the carbon content in steel does not exceed 1.7%.

HARDENING

• Hardening is a heat treatment process in which steel is heated to 30-50.C above the critical range. Soaking time is allowed to enable the steel to obtain a uniform temperature throughout its cross section. Then the steel is rapidly cooled through a cooling medium.

TEMPERING

• Tempering is a heat-treatment process consisting of reheating the hardened steel to a temperature below 400.C, followed by cooling.

• Purpose of tempering the steel:-1. To relieve the internal stresses2. To regulate the hardness and toughness3. To restore some ductility • Process of tempering the steel:- The tempering process consists of

heating the hardened steel to the appropriate tempering temperature and soaking at this tempering, for a definite period.

ANNELING

• Definition:- The annealing process is carried out by heating the steel above the critical range, soaking it for sufficient time to allow the necessary changes to occur, and cooling at a predetermined rate, usually very slowly witching the farness.

• Purpose :- 1. To soften the steel.2. Ti improve the machinebility.3. To increase the ductility.4. To relieve the internal stresses.

• Process:- Annealing consists of heating of hypo eutectoid

steels to 30t50’c above the upper critical temperature and 50’c above the lover critical temperature for hypereutectoid steels.

NORMALISING

Definition:-The process of removing the internal defecate or to refine the structure of steel components is cold normalizing.

Purpose:- • To produce fine grain size in the metal.• To reduce ductility.• To prevent warping.

SURFACE HARDENING OF STEEL

• Most of the components must have a hard, wear resisting surface supported by a tough, shock resisting core for better service condition and longer life. This combination of different properties can be obtained in a single piece of steel by surface hardening.

TYPES OF SURFACE HARDENING

• Case hardening • Nitriding• Flame hardening• Induction hardening

CASE HARDENING

• Parts to be hardened by this process are made from a steel with a carbon contact of 0.15% so that they will not respond to direct hardening.

• The steel is subjected to treatment in which the carbon contact of the surface layer is increased to about o.9%.

CARBURISING

• In this operation the steel is heated to a suitable temperature in a carbonaceous atmosphere, and kept at that temperature untill the carbon has penetrated to the depth required.

• The carbon can be supplied as a solid, liquid or gas.

NITRIDING

• Gas nitriding • Nitriding in salt bath • Process• Advantages

FLAME HARDENING

• In This type of hardening, the heat is applied to the surface of the work piece by specially constructed burner.the heat is applied to the surface very rapidly and the work is quenched immediately by spraying it with water.

ADVENTAGE OF FLAM HARDNING

• The hardening devices are brought to the work piece.

• Short hardening time.• Great depth of hardening.• Easily controlled.• Small Distortion.• Low fuel consumption.

INTRODUCTION HARDNING

• This a production method of surface – hardening in which the part to be surface – hardened is pleased within an inductor coil through which a high frequency current is passed. The depth of hardening for high frequency current o.7 to 1.0mm.the depth of hardening for medium frequency current is 1.5to2.0mm. Special steel and unalloyed steels with a carbon content of 0.35t00.75% are used.