IV Sem Mech_mt -II Lab Manual

R.M.K. COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF MECHANICAL ENGINEERING

ME2258 - MANUFACTURING TECHNOLOGY LAB-II

LAB MANUAL

II YEAR / IV SEMESTER MECHANICAL

ME2258 - MANUFACTURING TECHNOLOGY LAB-II Page 1 of 94


ME2258 MANUFACTURING TECHNOLOGY LAB II L T P C

0 0 3 2

OBJECTIVE

To give practical hands on exposure to students in the various metal cutting operations using commonly

used machine tools

EXERCISES

1) Two or More Measurements in Metal Cutting Experiment (Example: Shear Angle, Cutting

Force, Tool Wear etc.)

2) One or More Exercises in Shaper, Slotter, Planner, Drilling, Milling Machines (Example: Round

to Square, Dovetail in shaper, Internal keyway cutting in Slotter, Round to square in Planner,

Drilling, reaming and tapping in Drilling machine, Gear Milling and Keyway milling in Milling

machine.)

3) Two or More Exercises in Grinding / Abrasive machining (Example: Surface Grinding,

Cylindrical Grinding.)

4) Two or More Exercises in Assembly of Machined Components for different fits. (Example: Parts

machined using Lathes, Shapers, Drilling, Milling, and Grinding Machines etc.)

5) One or More Exercises in Capstan or Turret Lathes

6) One or More Exercises in Gear Machining (Example: Gear Milling, Gear Hobbing etc.)

LIST OF EQUIPMENT

(For a batch of 30 students)

1. Centre Lathes - 2 Nos.

2. Turret and Capstan Lathes - 1 No.

3. Horizontal Milling Machine - 1 No.

4. Vertical Milling Machine - 1 No.

5. Surface Grinding Machine - 1 No.

6. Cylindrical Grinding Machine - 1 No.

7. Shaper - 2 Nos.

8. Slotter - 1 No.

9. Planner - 1 No.

10. Radial Drilling Machine - 1 No.

11. Tool Dynamometer - 1 No.

12. Gear Hobbing Machine - 1 No.

13. Tool Makers Microscope - 1 No.

R.M.K. COLLEGE OF ENGINEERING AND TECHNOLOGY Page 2 of 94


TOTAL: 45 PERIODS



INDEX

S.No Experiments Date Mark Signature

Lathe and Lathe Works

1. Lathe Tool Dynamometer

2. Power measure In Lathe Machine

3. Assemble Fits

Capstan & Turret Lathe Machines

4.Turning, Facing, Drilling, Threading, Reaming & Knurling using Capstan

Milling Machines (Plain & Vertical Milling Machine)

5.External Keyway By Vertical Milling Machine

6. Round to Hexagonal Mill Machine

7.Gear Cutting By Horizontal Milling Machine

Grinding Machines (Surface & Cylindrical Grinding)

8. Surface Grinding

9. Cylindrical Grinding

Shaper Machine

10. Round To Square By shaper Machine

Slotter Machine

11. Internal Keyway By Slotter Machine

Planner Machine

12. Round To Square By Planner Machine

Drilling Machine (Pillar & Radial Drilling Machines)

13. Drilling, Reaming and Tapping

Gear Hobbing Operation

14. Helical Gear By Gear Hobbing Machine



INTRODUCTION TO MANUFACTURING PROCESSES

The materials, which conic under the ambit (field) of materials science, are available either

from nature or from industry. Whether from nature or industry, these materials cannot be used in

their raw forms for any purposeful use.

The materials are generally shaped and formed into various useful components through

different manufacturing processes in order to fulfill the day-to-day needs of the industries.

Manufacturing converts the raw materials into finished products to be used for some

purposes. Manufacturing process is a fundamental area since it is of interest not only to

mechanical engineers but also to engineers from other disciplines of engineering.

There are various manufacturing processes by which a product can be made of each process,

however, has its own limitations, restrictions and owing to this reason, a particular process is

adopted to certain specified applications.

Thus, while a product can be manufactured by two or more processes, the real

problem is to select the most economical one amongst the alternatives.

CLASSIFICATION OF MANUFACTURING PROCESS:Manufacturing processes can be classified as under:

Casting, foundry or moulding processes. Joining and assembly processes

Forming or Metal working processes Surface treatments (finishing) processes

Machining (Metal removal) Processes Heat treatments.

CASTING FOUNDRY OR MOULDING PROCESSES

Casting is one the oldest manufacturing processes. Casting needs molten metal and a cavity

of a refractory material. The metal retains the desired shape of the mould cavity after solidification.

An important advantage of casting process is that, in a single step, material can be

converted from a crude form into a desired shape. In most cases, secondary advantage is that excess

or scrap material can be recycled. The process is equally suitable for the production of a very

small batch and as well as on a very large scale. Casting and moulding processes are converted in the

later part of this study material. There are two types of casting classification namely, permanent

mould (for repeated use) and non — permanent mould (for single use).

FORMING OR METAL WORKING PROCESSES

Flaming and shearing operations typically utilize material that has been previously cast or

moulded. In a forming process, metal may be heated to a temperature which is slightly below the

solidus temperature and then a large force is applied such that the material flows and takes the

desired shape. The desired shape is controlled by means of a set of tolls called dies which may be

completely or partially closed during the manufacture. These processes are used normally for large-

scale production. In case of series operations, the final form of material is the result of all prior

operations.



Thus, forming and shearing modify the shape and size and improve the mechanical

properties too. Forming and shearing operations are done on metal in both "hot" and "cold" state,

and temperature of the material during process is important with respect to its temperature of re-

crystallization.

Some of the processes are: rolling, drop forging, press forging, upset forging, extrusion, wire

drawing, sheet metal operations, etc...

MACHINING (OR) METAL REMOVING PROCESSES

Machining and processes are linked with the removal of a specific portion to get the desired shape

(or finish); the additional unwanted material is removed in the form of chips from the blank

material by a cutting tool so as to obtain the final desired shape. Chips are formed when material is

machined with a cutting tool.

The cutting tools are mounted in machine tools, which provide the movements to the tool with

respect to the job to accomplish the desired process.

Material removals are normally the most expensive methods because more energy is

consumed and also a lot of waste material is generated in these processes.

Machining is widely used because it delivers very good dimensional accuracy and accurate

surface finish. It generates accurate contours too.

Metal Removing (Machining) is the process of removing unwanted material from a work piece in

the form of chips. If the work piece is metal, the process is called metal cutting.

Different materials behave differently. The levels of strain, strain rate, temperature are high.

The process is sensitive to variation in tool geometry, tool material, temperature, the cutting

environment (cutting fluids) and process dynamics.

Special machines are used to obtain productivity, accuracy, economy with surface of better

quality. It includes semi-automates, capstan and turrets, planning, milling, surface grinding,

boring machines etc..,

All cutting process require a cutting tool harder than the work with required cutting

angles of suitable materials like FISS, high carbon steel, tool steel, coated tools (CVD,

PVD), ceramic or diamond. The tool must be strong wear resistant and should not change its

state and even at high (1000° C) temperature. (Form stability)

Machine used for machining are two types:

Conventional & Non — Conventional

Non — Conventional is EDM, ECM, LBM, USM etc..,

Conventional machines are Lathe, Shaper, Miller, Driller, Slotter, and Grinder: Machining

involves energy to create a surface required form & finish. Electrical energy is converted into

mechanical energy and while cutting, energy is lot in the form of heat. Almost all process requires

machining at some particular stage.



Classification of tool materials: -

The tool materials may be classified into three categories, namely:

Ferrous tool materials, Non — metallic tool materials & Non ferrous tool materials

Ferrous tool materials: - Ferrous tool materials have iron as their chief constituent. High

carbon steel (tool steel) and high speed steel belong to this group.

Non - ferrous tool materials: - Non - ferrous tool materials do not have iron, and cast by

alloying elements like tungsten, vanadium, molybdenum etc. satellite belongs to this group.

Carbide which is also of non ferrous tool materials manufactured by powder metallurgy

technique carbon and tungsten are the chief alloying elements in this process.

Properties of good cutting tool materials:-. At the end of this lesson you shall be able to

Qualities of good cutting tool materials.

The characteristics of cold hardness, red hardness and toughness

The factors to be noted when selecting a tool material

Finishing processes

Finishing processes are yet another class of processes typically employed for cleaning,

removing of burrs left by machining or providing protective surface layers on the work pieces.

Surface treatment includes plating, galvanizing, and anodizing, mechanical, chemical cleaning.

Heat Treatment

Heat treatment involves the heating and cooling of a metal for specific purpose of

altering its mechanical and metallurgical properties and improving the performance of the

metals.



SAFETY PRECAUTIONS

A good craftsman, having knowledge of various safety precautions, can avoid accident to

himself and to his fellow workers and protect the equipment from damage. To achieve this, it is

essential that every person should follow the safety procedures (Fig l). Safety in a workshop can be

broadly classified into 3 categories (a) General Safety, (b) Personal Safety, and (c) Machine Safety.

General safety: -

Keep the floor and gangways clean and clear.

Move with care in the workshop, do not run.

Don't leave the machine which is in motion.

Don't touch or handle any equipment / machine unless authorized to do so.

Don't walk under suspended loads.

Don't cut practical jokes while on working.

Use the correct tools for the job.

Keep the tools at their proper place.

Wipe out split oil immediately.

Replace worn out or damage tools immediately.

Never direct compressed air at yourself or at your co worker

Ensure adequate light in the workshop.

Clean the machine only when not in motion.

Sweep away the metal cuttings.

Know everything about the machine before you start it.

PERSONAL SAFETY: -

Wear a one piece overall or boiler suit.

Keep the overall buttons fastened.

Don't use ties and scarves.

Roll up the sleeves tightly above the elbow.

Wear safety shoes or boots and goggles.

Cut the hair short.

Don't wear a ring, watch and chain.

Never lean on the machine.

Don't clean your hands in the coolant fluid.

The work area is clear.

Don't use (Jacked or chipped took.

Don't start the machine until:


The work piece is securely mounted.

The feed machinery is in the neutral.

Don't remove the guards when the machine in motion.

Don't adjust damps or holding devices while the machine is in motion.

Never touch the electrical equipment with the wet hands.

Don't use any faulty electrical equipment.

Ensure that electrical connections are made by an authorized electrician only.

Concentrate on our work.

Have calm attitude. Do things in a methodical way.

Don't engage yourself in conservation with others while concentrating on your job.

Don't distract the attention of others.

Don't try to stop a miming machine with hands.

Machine Safety

Switch off the machine immediately if something goes wrong.

Keep the machine clean.

Replace any worn out or damaged accessories, holding devices, nuts, bolts etc as soon as possible.

Do not attempt operating the machine until you know how to operate it properly.

Do not adjust the stroke, tool or the work piece unless the power is off

Stop the machine before changing the speed.

Disengage the automatic feeds before switching off.

Check the oil level before starting the machine.

Before starting the machine, move the ram by hand to ensure that the ram or tool-holder does not

strikes the work piece or table.

Never start the machine unless all the safety guards are in position.

Take measurements only after stopping the machine.

Use wooden planks over the bed while loading and unloading heavy jobs.

Do not stop the machine before the finish of the cutting stroke.

Points To Be Noted When Selecting a Tool! Via trial

Condition and form of material to be machined


ME2258 - MANUFACTURING TECHNOLOGY LAB-IIMaterial to be machined

Condition of the machine tool available

The total quality of production and rate of production involved.

The dimensional accuracy required and the quality of surface finish.

The amount of coolant applied and the method of application.

The skill of the operator

TOOL MATERIALS:

Metal putting tool materials perform the function of cutting. These materials must be

stronger and harder than the material to be cut. They must be sufficiently tough to resist shock

loads that result during cutting operations. They must have good resistance to abrasion and a

reasonable tool life.

The three important basic qualities that any cutting tool material should possess are

Cold hardness, Red hardness and Toughness.

Cold hardness:

It is the amount of hardness possessed by a material at normal temperature. Hardness is the

property possessed by which if can cut other metals, and has the ability to scratch on other metals. When

hardness increases, brittleness also increases, and a material which is having too much of cold hardness is

not suitable for the manufacture of cutting tools.

Red hardness:

It is the ability of a tool material to retain most of its cold hardness even at very high temperature.

During machining, due to friction between tool and work, tool and chip, heat is generated, and the tool

losses its hardness and its efficiency even when the temperature during cutting increases, then the metal

possesses the property of red hardness.

Toughness:

The property possessed by a material to resist sudden load that results during metal cutting is

termed as 'toughness'. This will avoid the breakage of the cutting edge.


THE LATHE AND ITS PRINCIPLE OF WORKING

A bathe is one of the oldest and perhaps (possibly) most important machine tools

ever developed. The job to be machined is rotated (turned) and the cutting tool is moved

relative to the job. That is why; the lathes are also called as turning machines.

If the tool moves parallel to the axis rotation of the work piece, cylindrical surface

is produced, while, it moved perpendicular to this axis, it produces a flat surface. A

lathe was basically developed to machine cylindrical surfaces.

On the basis of their purpose, design, number of tools accommodated, degree of

mechanization and other factors, lathe-type machine tools may be classified as:

Machining is a process of reducing the given work piece into the required shape and size with

the hell) of a machine tool. In simple words, machining is a process of removing certain

material from the work piece.

The Lathe can be defined as a machine tool which holds the work between two rigid and

strong supports called centers, (or) in a chuck (or) face plate while the latter revolves. The chuck or

the face plates is mounted on the projected end of the machine spindle.

The cutting tool is rigidly held and supported in a tool post and is fed against the

revolving work.

While the work revolves about its own axis the tool is made to move either parallel to (or)

at an inclination with this axis to cut the desired material.

In doing so it produces a cylindrical surface, if it is fed parallel to the axis, (or) will

produce a tapered surface if it is fed at an inclination.

A lathe is a father of all machine tools. It is the most important machine used in any

workshop. The function of a lathe is to remove metal from a piece of work to obtain the required

shape and size. A lathe removes metal by rotating the work piece against a single point cutting tool.

Generally, lathe is used to machine cylindrical shapes. The parts to be machined can be held

between two rigid supports called live and dead centers. The tool is moved perpendicular to the work

piece axis to produces a flat surface. The tool is moved at an angle to the axis of work piece to

produce tapered surface.

The fo l lowing Opera t ions can be done by us ing la the : Fac ing, Turning,

Taper & Step Turning, Eccentric Turning, Chamfering, Drilling, Boring, Reaming,


ME2258 - MANUFACTURING TECHNOLOGY LAB-IITapping, Knurling, Forming, Grooving, Polishing, Spinning, Thread Cutting, etc..,

1. Limited or low production machines.

The lathes included in this category are:

Engine lathe (center lathe), Bench lathe, Tool room lathe and Speed lathe.

2. Medium-production machines.

Capstan end Turret lathes, and duplicating or (tracer controlled) lathes.

3. High -production machines.

Semi automatic and automatic lathes,

Cutting Speed

It is a peripheral speed of the work past the cutting tool.

It is the speed at which metal is removed by the tool from the work piece.

It is expressed in meter / minute.

C u t t i n g s p e e d = d e p t h o f c u t x Diameter x R.P.M / 1000

Feed

It is defined as the rate of tool across a surface cutting it.

It is the distance the tool advances for each revolution of the work piece.

It is expressed in an / revolution.

Cutting Tool Forces

The deformation of a work material means that enough forces have been exerted by the tool

to permanently reshape of the work material. The cutting action and the chip formation can be

more easily analyzed if the edge of the motion of the material. Cutting tool forces are three types.

They are (1) Tangential force, (2) Longitudinal force and (3) Radial force.

A. Tangential force - This Tangential force acts in a direction tangential force to the

revolving work piece and represents the resistance to the rotation of the work piece.

B. Longitudinal force - Longitudinal force acts in the direction parallel to the axis of the work

and represents the resistance to the longitudinal feed of the tool.

C. Radial force - Radial force acts in a radial direction from the center line of the

work piece. The radial force is generally the smallest of the three, of about 50 percent as large

as longitudinal force.


L A T H E D I A G R A M


ME2258 - MANUFACTURING TECHNOLOGY LAB-IIDepth of Cut:

It is the perpendicular distance measured from the machined surfaces to the uncut surface of work. It is

expressed in mm.

Depth of Cut = d1-d2 / 2

Where:

d1 ---- diameter of work before machining & d2 ---- diameter of work after machining.

TYPES OF LATHE MACHINE: -

Bench Lathe: It is a very small lathe and is mounted on a separately prepared bench (or) cabinet. It is

used for small and precision work since it is very accurate.I

Speed Lathe: These lathes may be of bench type or they may have the supporting legs cast and

fitted to the bed.

Engine Lathe: It is probably the most widely used type of lathe It is also known as Centre lathe.

Tool Room Lathe: It is nothing but the same engine lathe but equipped with some extra attachments to

make it suitable for a relatively more accurate and precision type of work carried out in a tool room.

It carries a much wider taper turning attachment, follower rest, collects, chucks etc., the most

commonly used lengths are 135 to 180cm.

Capstan and Turret Lathes: These lathes form a very important and useful group and are vastly

used in mass production. These machines are actually of semi-automatic type and a very wide range of

operations can be performed on them.

Automatic Lathe: These lathes help a long way in enhancing the quality of production. They are so

designed that all working and job handling movement of the complete manufacturing process

for a job are done automatically.

Special-Purpose Lathe: A large number of lathes are -designed to suit a definite class of work and to

perform certain specified operations only. They can be further classified according to the type of

drive they posses and their sizes, etc., According to the height of centers (above the bed) lathes can be

grouped as,


Parts of the Lathe Machine

1. BED

The bed of a lathe acts as the base on which the different fixed and operating parts of the lathe are mounted.

2. HEAD STOCK

The head stock is that part of the lathe which serves as housing for the driving pulleys

and back gears, provides bearing for the machine spindle and keeps latter in alignment with the

bed.

I) Cone pulley, H) Back gears and back gear lever, III) Main spindle (or) head stock spindle, IV)

Live centre and V) Feed reverse lever.

3. FEED MECHANISM AND CHANGE GEARS

The gear mechanism operated by means of the feed reverse lever is called the tumbler

reversing mechanism. It will be seen that the motion from the spindle to the lead screw or feed rod

is transmitted through this mechanism.

4. TAIL STOCK

It is also sometimes called the loose head-stock or puppet head. It is mounted on the bed of

the lathe such that it is capable of sliding along the latter maintaining its alignment with the head

stock.

It is a movable casting. On common type's medium size and small size of lathes it is moved

along the bed by hand, where as in heavier type of lathes, it is moved by means of a hand wheel

through a pinion which meshes with the rack provided on the front of the lathe bed.

Sleeve or barrel, b. Dead centre, c. Hand wheel, and d. Bearings and Screwed spindle(s)

5. CARRIAGE: -

The carriage serves the purpose of supporting, guide, and feeding the tool against the job during

the operation on the lathe.

Saddle: - It is part of the carriage which slides along the Bed ways and supports the Cross-

Slide, Compound Rest and Tool Post.

Apron mechanism and Swivel plate.

6. LEGS

They are supports which carry the Entire Load of the Machine over them. The prevailing

practice is to use cast legs. Both the legs are firmly secured to the flour by means of foundation

bolts in order to prevent vibrations in the machine.


ME2258 - MANUFACTURING TECHNOLOGY LAB-IIWORK HOLDING DEVICES

Lathe Accessories or Work holding devices:

The common work holding devices used for a centre lathe are discussed below: I.

1. Centers: (Live and Dead Centre)

2. Chucks: Three jaw universal chuck, tour jaw independent chuck, combination

chuck, Magnetic chuck, air or hydraulic chuck and collet chuck.

3. Face plate, 4. Angle plate, 5. Driving plate, 6. Mandrels,

7. Stead rests (fixed steady rest and follower or traveling steady rest).

8. Milling vise: Milling vise is mounted in place of the compound rest. The work is held in the

vise and an end mill or stub-arbor mounted cutter is inserted in the lathe spindle. , Work

movement is limited.

LATHE CENTERS

Used to support work.

Have two categories of centers.

Live centre fitted in the headstock spindle.

Dead centre is one which is fitted in the tailstock.

CHUCK

Device used to hold a job.

Easily fitted on the thread cut on the end of headstock spindle.

Type of Chucks are

Two jaw chuck. > Four jaw chuck. > Magnetic chuck

Three jaw chuck. > Collet chuck

FACE PLATE

A circular plate screwed to lathe spindle.

Used for mounting the type of jobs which cannot be held by chucks?

More number of holes and slots on the faces of the face plate.

CATCH PLATE

A plain disc of steel or cast iron screwed to the nose of the headstock spindle.

To drive the work piece through a carrier or dog when it is held between the centers.

LATHE CARRIERS OR DOGS

Used for transferring the motion from the rotating driving plate to the work held between the centers.

Used for connecting end of work piece to the driving plate.


Berg IS Carrier

Bent tail carrier

Types of Lathe Carriers or Dogs

Bent Tail.

Straight Tail.STEADY REST

Clamp Type.

To support long work piece between the centers or by a chuck.

Used for cylindrically long jobs.

Two types of steady rest are

Fixed Steady rest. Traveling Steady rest.

MANDREL

To hold hollow jobs.

A hardened piece of round bar for holding bored or reamed jobs.

Contains drill holes at both the ends.

Work piece is mounted over the mandrel.


FOLLOWER REST

Made of cast iron for supporting long slender work pieces against the cutting tool foredo.

Clamped to the carriage of the lathe to make it travel along the cutting tool.

Have two adjustable jaws to support the work piece.

Two Supporting jaws resist the cutting forces.

Vender Caliper Mader Setters

Salida plate

Steal Rale

Vander Hight Gauge

Four J aw Chuck

Magnetic Chucks

Collet Chuck Face Plate

Body

Three Jaw Chuck Universal

Four Jaw Chuck Universal

MARKING AND MEASURING TOOLS

The following table illustrates various marking and Measuring wok and their

characteristics and uses.

Tools CharacteristicsUses

Steel rule

It is made of tempered steel about 3/64

inch thick, 3/4 inch wide and 6 inch hang

with several styles of graduation.

It is used to take linear measurements up

to accuracy of 0.5mm.

Vernier CaliperGraduations are made on both sides of

the bar.

It is a tool for checking Inside and

Outside measurements. It is. Also used as

depth gauge.

Vernier Height

Gauge

It consists of an upright steel bar fixed to

a steel base. On the bar, there is a

Movable jaw with Vernier scale The

screw is used to adjust the Vernier scale

to a required position.

It is used to scribe lines on a work piece

to known heights.

Scriber A scriber is a sharp pointed steel tool. It

is made of carbon tool steel,

It is used to scribe or mark lines on metal

work pieces.

Try Square

It is a small, light square that has a

hardened steel blade without graduations.

It has two parts namely blade, beam.

Try square is used to check the flatness

and square ness of the work piece.

Dot Punch

It is made of Steel. The angle of the

conical point is usually along marked

lines and to 60°.

It is used to make dots along marked

lines and to provide small centre mark

for divider point etc.,

Surface PlateIt is made of grey cast iron and of solid

design (or) with ribs.

It is used for testing the flatness of work

and also used for carrying the work piece

while marking.CUTTING TOOLS ANGLES

TOP RAKE ANGLE (BACK RACK ANGLE)

If the slope is given to the face or surface of the tool and if this slope is along the tool's length

then it is called top rake angle.

Usual1y15° to 20°.

SIDE RAKE ANGLE

If the slope is given to the face or top of the tool along the tool's width then it is called side rake

angle.

Lies between 6° and 15°.

CLEARANCE ANGLE (RELIEF ANGLE)Side clearance angle-It is an angle, the side cutting edge makes with the axis of the tool.End clearance angle.It is an angle, the End cutting edge makes with the width of the tool

THIS WILL HELP YOU TO IDENTIFY A RIGHT-CUT AND A LEFT-CUT TOOL.

COMMON CUTS MADE BY DIFFERENT CUTTING TOOLS.

OPERATIONS IN

TURNING

Turning is not a single process but class of many and different operations performed on a lathe.

Turning of Cylindrical Surfaces

The lathe can be used to reduce the diameter of a part to a desired dimension The resulting machine Surface is cylindrical.

straight turning plunge turningTurning of Flat Surfaces

A lathe can be used to create a smooth, flat face very accurately perpendicular to the axis of a cylindrical part. Tool is fed radially or axially to create a flat machined surface.

Threading facing tube turning parting tasting-off}

Different possibilities are available to produce a thread on a lathe. Threads are cut using

lathes by advancing the cutting tool at a feed exactly equal to the thread pitch. The single-point

cutting tool cuts in a helical band, which is actually a thread. The procedure calls for correct settings

of the machine, and also that the helix be restarted at the same location each time if multiple passes

are required to cut the entire depth of thread. The tool point must be ground so that it has the same

profile as the thread to be cut. Another possibility is to cut threads by means of a thread die

(external threads), or a tap (internal threads). These operations are generally performed

manually for small thread diameters.

threading die threading tap threading

Form TurningCutting tool has a shape that is imparted to the work piece by plunging the tool into the

work piece. In form turning, cutting tool is complex and expensive but feed is linear and does not

require special machine tools or devices.

comingContour Turning (Profiling)T

Cutting tool has a simple shape, but the feed motion is complex; cutting tool is fed along a contour thus creating a contoured shape on the work piece. For profiling, special lathes or devices are required.

Producing tapers on a lathe is a specific task and contour turning is just one of the possible

solutions. Some other methods for turning tapers are discussed later.

Contour turning (profiling) Miscellaneous Operations

Some other operations, which do not use the single-point cutting tool, can be performed on a lathe, making turning one of the most versatile machining processes.

Knurling

plunge grooving face grooving

This is not a machining operation at all, because it does not involve material removal. Instead, it

is a metal forming operation and used to produce a regular crosshatched pattern in the work surface.

SAFETY PRECAUTIONS FOR LATHE MACHINING WORK

Job should be held tightly in the chuck.

If the job is held in between the centers, then apply grease on the nose of dead centre,

otherwise it will burn out due to excess heat.

Do not measure the job while the work piece is rotating.

Do not leave the chuck key in the chuck.

Do not try to stop the lathe chuck or job with hands.

Do not handle metal chips by hand. .

Do not give more depth of cut while the job is rotating at high speed.

Tighten the tool in the tool post.

Do not Stand close to the rotating work piece or bring your face to it.

Do not reduce or increase the speed during lathe operations.TERMINOLOGIES USED IN THREAD CUTTING OPERATION

S. No TerminologyDescription Symbol

1. Pitch Distance measured from a point on one thread

to the corresponding point on adjacent thread.

P

2. Major

Diameter

Outside diameter of the threaded part measured_

perpendicular to the axis of the work piece.

D

3.Minor

Diameter

Inner diameter of the threaded part measured

perpendicularly to the axis of the work piece.

d

4.Depth of

thread

Distance measured at right angle to the axis

of the screwed part, between the crest and

root of the thread.

T ,

(Left) Knurling operation; (Right) Knurling tool and knurlingwheal. Wheels with different patterns are easily

THREAD CUTTING

It is a process of making threads on the work piece.

Thread cutting tool is used for this operation.

Power feed is given to the carriage through lead screw and for one rotation of the job. It covers the distance equal to the pitch.

Depth of cut is small for thread cutting.

TYPES OF THREAD

RIGHT HAND THREAD:

View the screwed part of the thread in a direction normal to its axis, if the threads found

sloping downwards from top from left to right then it is right hand thread.

LEFT HAND THREAD:

If the threads found sloping downwards from top from right to left, then it is called left

hand thread.

THREAD CUTTING OPERATION

PRINCIPLE: Producing helical groove on a cylindrical or conical surface by feeding the tool

longitudinally by holding the job between the centers or by a chuck.

TOOL USED: Threading tool

OPERATION

While cutting threads, the work is held between centers.

Then the job is turned to the size of the major diameter of the thread to be cut.

Change gears of correct sizes are calculated and fitted between the lathe spindle and the lead

screw. ,The speed of the job is reduced to one-third or one-fourth of the job speed used in turning

operation.

The

half nut makes the carriage to engage or disengage the lead screw and the rotation of the lead screw is

used to traverse the tool along the work to produce screw threads,

CALCULATION OF CHANGE GEARS

Longitudinal feed of the tool = Pitch of the thread to be cut per revolution of the work piece.

The definite ratio between the longitudinal feed and the rotation of the head stock spindle should be

found out so that the relative speeds of rotation of the work and the lead screw will result in the cutting

of a thread of the desired pitch.

This is affected by the change gears arranged between the spindle and the lead screw.

TOOL MATERIALS

The single point lathe cutting tools are made of high speed steel. (11SS.). The main alloying elements are 18% tungsten, 4% chromium and 1 % vanadium and 5 to 10 percent cobalt. Cobalt to improve the heat resisting properties of the tool. For general purpose, carbon steel or tool steel used. Carbide tipped tools fixed in tool holders, are mostly used in production

Specification of Lathe Machine: -(4.5 feet Lathe Machine) Precision grade I accuracy lathe

flame hardened with gap bed motorized t od el. Belt driven lathe size 4.5 feet standard accessories.

Expt. No: Lathe Tool Dynamometer Date:

MODEL MTT 632

HEIGHT OF CENTRE 165 MMSWING OVER BED 330 MMSWING OVER CARRAIGE 180 MMBED WIDTH 180 MMDISTANCE BEI_WEEN CENTRES 1000 MMSPINDLE BORE 38 MMTAPER OF SPINDLE BORE MP 5NO. OF SPINDLE SPEEDS 8RANGE OF SPINDLE SPEED 65-1810 RPMTTATL STOCK TAPER MT-3RANGE OF LONGITUDINAL FEED 0.0527-1.2912 MM/REVRANGE OF CROSS FEED 0.014-0.344 MM/REVRANGE OF METRIC THREAD 0.4- 7 MMRANGE OF INCH THREAD 4 — 60 TPIMOTOR POWER 1.511P/3PHASE

AIM: - To measure the principal cutting forces in orthogonal machining by a lathe tool dynamometer.

APPARATUS REQUIRED: - Seamless tube, Strain gauge, Lathe tool dynamometer

TOOLS REQUIRED: - Carbide tip tool with side rake angle 20 degrees, Vernier caliper, Adjustable spanner, Tool post key, Chuck key, Revolving center etc

MATERIALS REQUIRED: - A cylindrical work piece of diameter________mm and length________mm of mild steel rod.

Specifications of Apparatus Used & Centre Lathe Machine: - M O D E L M T T 6 3 2 HEIGHT OF CENTRE 165 MMSWING OVER BED• 330 MMSWING OVER CARRAIGE 180 MMBED WIDTH 180 MMDISTANCE BETWEEN CENTRES 1000 MMSPINDLE BORE 35 MMTAPER OF SPINDLE BORE MI-SNO. OF SPINDLE SPEEDS 8RANGE OF SPINDLE SPEED 65-1810 RPMTAIL STOCK TAPER MT-3RANGE OF LONGITUDINAL FEED 0.0527-1.2912 MM/REVRANGE OF CROSS FEED 0.014-0.344 MM/REVRANGE OF METRIC THREAD 0.4- 7 MMRANGE OF INCH THREAD 4 — 60 TRIMOTOR POWER 1.5HP13PHASE

LATHE TOOL DYNAMOMETER:

The lathe tool dynamometer enables to measure x, y and z at different cutting conditions. This

dynamometer consists of a tool holder held rigidly in the dynamometer body. Sensing is done using sensor

which resistance strain gauges are mounted. The dynamometer is mounted on the lathe on tool post.

Bridge balance unit: -

a) The Bridge balance unit consists of :

b) Power supply unit to supply power to both the bridges.c) Two bridge circuits for vertical and horizontal force components with the balancing ports

for initial zero setting of the bridge circuits.

Calibration: -

The dynamometer is precisely calibrated for vertical & horizontal forces and the corresponding output recorded. The calibration is done with help of proving ring and the output in direct Kgf. for all the components.

Operating instructions for bridge balance unit: -a) Place the sensing unit of dynamometer in proper position.

b) With the help of cables provided carefully connect PU1 and PU2 cables on sensing unit to PUI and PU2 sockets on force indicator unit.

c) Connect( force indicator to 230 V, single phase supply and switch 'ON' supply.d) Now instrument is ready for use.

e) Obtain balance on each channel by operating balance pot on / indicator for both channels under

specified conditions.

Procedure: -

a) Mount the dynamometer on the tool post of the lathe and clamp it rigidly as shown in fig.

b) Mount work piece in the chuck.

c) Adjust the feed and speed of the lathe machine and start the machine. Feed the tool manually

to start cutting and feed it automatically.

d) Wait to stabilize the output of the bridges and measure the maximum output for vertical and

horizontal forces.

e) The vertical and horizontal forces on the dynamometer should not exceed the limit of 500 Kgf. (for safely purpose work up to 300 Kgf.)Precautions: -a) Amphonel socket connections must be done carefully. Se that during actual use of the instrument they are not damaged or spoiled in anyway

b) Zero adjustment must be done carefully.

c) Do not apply excessive loads on the sensing unit than specified.

d) To ensure long life, the balance pots must also be operated very carefully.Table: 1

Spindle Speed - ......................... rpm

Constant feed - ............ rpm / rev.

S. NoDepth of

CutChip Thickness Fv, (Kgf.) FH (Kgf.)

Chip Thickness Ratio(r)

Shear Plane Angle (Ø)

I. 0.5 mrn

2. 1.0 mm

3. 1.5 mm

Specimen Calculation: -Chip Thickness Ratio = (r) = (t/tc) Shear Plane Angle (Ø) = tan-1(r cos α / (1 - r sin α))Shear plane forces(Fs, Ns): Where:-Fs = FH cosØ – Fv sinØ Fv = Cutting Force in kg f.Ns = Fv cosØ - FH sinØ FH = Feed Force in kg f.Tool Plane Forces (F, N): Fs = Shear Force in kg f.F = Fv cosα + FH sinα Ns = Normal to shear force in kg f.N = FH cosα + Fv sinα F = Frictional force

N = Normal to frictional forceGraph: - α = Rake angle of the tool.

a) Depth Of Cut Vs Feed Force

b) Depth Of Cut Vs Cutting Force

c) Draw Neatly the Merchants Circle.

Diagram:-

Orthogonal Cutting

Result: -

The Principle cutting forces in orthogonal machining by lathe tool dynamometer is measure successfully.

Ex. No: Assembly Fits Date:AIM: - To machine the components for interference and interference fits based on the hole basis system.TOOLS REQUIRED: - H.S.S. turning tool, Vernier caliper, Adjustable spanner, Tool post key, Chuck key, Revolving center, Shaft with key. Bearing, Pulley, Micrometer etc...MATERIALS REQUIRED: - A cylindrical work piece of diameter ...mm and length ...mm of mild steel rod.THEORY: - A machine is built by assembling all its consisting parts. During assembling

sometimes a parts may be required to be fitted into another part. In such case during the working of

the machine they may or may not be intended to have a relative motion between them. If there should

be relative motion between two parts, they must be fitted loose or tight fitting of one part into the

other; either loose or tight depends on the relationship existing between their mating surfaces, which

in turn depend on the dimensional differences between the parts. The relationship existing between the

mating surfaces of the parts, because of the differences in their dimensional, is called fit. Fits may be

classified into three different types viz:

a) Clearance fit

b) Interference fit

c) Transition fit

Clearance fit: - It is defined as the fit established when a positive clearance exists between the

dimensional of the hole and the shaft. It is obtained by selecting the maximum and minimum

limits of the shaft and the hole so that the clearance, due to the differences between the dimension

of the smallest possible and largest possible shaft, is always positive.

Basic size of the hole —

Minimum clearance —

Tolerance of the shaft

Tolerance of the hole - For hole basis system the minimum limit of the hole is equal to the basic size of the hole. Maximum limit of the shaft = lower limit of the hole — minimum clearance

Minimum limit of the shaft = maximum limit of the shaft — tolerance on shaftInterference fit: - It is defined as the fit established when a negative clearance exists between the size of the hole and the shaft. It is obtained by selecting the maximum and minimum limits of the shaft and the hole as that there is an interference of the surfaces and the clearance due to the difference between the dimensions of the largest possible hole and the smallest possible shaft is always negative.

Basic size of the hole =

Negative clearance =

Tolerance on shaft =

Tolerance on hole =

For hole basis system the minimum limit of the hole is equal to the basic size of the hole.

Maximum limit of the shaft = basic size the hole—maximum interference

Minimum limit of the shaft = maximum limit of the shaft — tolerance on shaft

Transition fit; r

It is defined as the fit established when the dimensions of the hole and the shaft are such that

there exists a positive clearance or a negative clearance when the shaft is fitted in to the hole. It is

obtained by selecting the maximum limits for the shaft and the hole such that there exists a positive

clearance when the smallest possible shaft is fitted in to the largest possible hole or as negative

clearance when the largest possible hole or a negative clearance when the largest possible shaft is

forced in to the smallest hole.

Hole basis system & shaft basis system

Hole basis system:

In this system, the different types of fits are obtained by associating shafts of various limit

dimensions with a single hole, whose lower deviation is zero. When the lower deviation of the hole

will be equal to its basic size, which is taken as the base for computing the other entire limit

dimensions the limit by selecting suitable clearances and tolerances ow the shaft and the hole

Shaft basis system:

In this system, the different types of fits are obtained by associating holes of varying limit

dimensions with single shaft, whose upper deviation is zero. When the upper deviation of the shaft

is zero the maximum limit of the shaft will be equal to its basic size, which is taken as the base for

computing all other limit dimensions

Procedure: -

1)Do the drilling operation on the given work piece with a standard size drill tool, such the diameter of

the hole is equal to the give basic size.

2)Calculate the diameter of the shaft for interference and clearance fits3) Perform the turning operations for clearance fit on one side of the shaft for a length of 50mm such that the diameter is within the minimum and maximum limit.

Diagram: -

Result: - Thus the given shaft is turned for clearance fit and interference fit.

CAPSTAN AND TURRET LATHE

The capstan or turret lathe consists of a bed, all geared headstock, and a saddle on which a

four station tool post is mounted to hold four different tools. A tool post fitted at the rear of the

carriage holds a parting tool in an inverted position. The tool post mounted on the cross-slide is

indexed by hand. In a capstan or turret lathe there is no tailstock, but in its place a hexagonal turret

is mounted on a slide which rests upon the bed. All the six faces of the turret can hold six or more

number of different tools.

The turret may be indexed automatically and each tool may be brought in line with the

lathe axis in a regular sequence.

The work pieces are held in collets or in chucks. The longitudinal and cross feed

movement of the turret saddle and cross-slide are regulated by adjustable stops.

These stops enable different tools set at different stations to move by a predetermined amount

for performing different operations on repetitive work pieces without measuring the length or

diameter of the machined surface in each case.

These special characteristics of a capstan or turret lathe enables it to perform a series of

operations such as turning, drilling, boring, thread cutting, reaming, necking, chamfering, cutting-off

and many other operations in a regular sequence to produce a large number of identical pieces in a

minimum time.

TYPES OF MACHINE'S

The two main types of horizontal lathes of this family are

1. The capstan or ram type lathe. 2. The turret or saddle type lathe.

The capstan or rain type lathes the ram type turret lathe or capstan lathe carries the hexagonal

turret on a ram or a short slide.

The ram slides longitudinally on a saddle positioned and clamped on lathe bed ways. This

type of machine is lighter in construction and is suitable, for machining bar of smaller diameter.

The tools are mounted on the square turret and six faces of the hexagonal turret. The feeding

movement is obtained when the ram moves from left to the right, and when the ram is moved backward

the turret indexes automatically and the tools mounted on the next face comes into operation

CAPSTAN AND TURRET LATHE

The standard engine lathe is versatile, but it is not a high production machine. When production requirements are high, more automated turning machines must be used. The turret lathe represents the first step from the engine lathe toward high production turning machines. The turret lathe is similar to the engine lathe except that tool-holding turrets replace the tailstock and the tool post-compound assembly. The 'skill of the worker' is built into these machines, making it possible for inexperienced operators to reproduce identical parts. In contrast, engine lathe requires a skilled operator and requires more time to produce parts that are dimensionally the same. The principal characteristic of turret lathes is that the tools for consecutive operations are set up for use in the proper sequence. Although skill is required to set and adjust the tools properly, once they are correct, less skill is required to operate the turret lathe.

Turret lathe parts. . . . .

ruvw4va, ) Neuf:anal hoot. 4, "e~ haer • a'J0114 .44k

Spindle speed selecto Square

turret Hexagonturret Turret

Ram slops

Forward and reverse

Stop rod

Longitudinal feed lever Carriage

handwheel

Cross-feed Feed selectorslever

Turnstile

Cross-slidehandwheel

Advantages of Turret Lathes

The difference between the engine and turret lathes is that the turret lathe is adapted to

quantity production work, whereas the engine lathe is used primarily for miscellaneous

jobbing, tool room, or single-operation work. The features of a turret lathe that make it a

quantity production machine are:

Tools may be set up in the turret in the proper sequence for the operation.

Each station is provided with a feed stop or feed trip so that each cut of a tool is the same as its previous cut. Multiple cuts can be taken from the same station at the same time, such as two or more turning and/or boring cuts.

Combined cuts can be made; tools on the cross slide can be used at the same time that tools on the turret are cutting.

Rigidity in holding work and tools is built into the machine to permit multiple and combined cuts.

Turret lathes can also have attachments for pre turning, thread chasing and duplicating, and can be made.

Differences between a Ram type or Capstan and Saddle type or a Turret lathe

The turret of a capstan lathe is mounted on a short slide or ram which slides on the saddle. The saddle is clamped on bed ways after adjusting the length of the work piece. Thus in a capstan lathe, the travel of the turret is dependent upon the length of the travel of the ram. This limits the maximum length of the work to be machined in one setting.

The turret of a turret lathe is mounted on a saddle which slides directly on the bed. This feature enables the turret to be moved on the entire length of the bed and can machine longer work.

In the case of turret lathe, the turret is mounted on the saddle which slides directly on the lathe bed ways. This type of construction provides utmost rigidity to the tool support as the entire cutting load is taken up by the lathe bed directly. In the case of a capstan lathe as the ram feeds into the work, the overhanging of the ram from the stationary saddle presents a non-rigid construction which is subjected to bending, deflection or vibration under heavy cutting load...

On a capstan lathe the hexagonal turret can be moved back and forth much more rapidly without having to move the entire saddle unit. Thus capstan lathes are particularly handy for small articles which require light and fast cuts. While operating the machine by hand, there is less fatigue to the operator, due to lightness of the ram, whereas in the case of turret lathe hand feeding is a laborious process due to the movement of the ensure saddle unit.

Some turret lathes are equipped with crosswise movement of the hexagonal turret. The crosswise movement may be effected by hand or power. This feature enables turning of large diameters, facing, contour turning and many other operation on the lathe.

Heavier turret lathes are equipped with power chucks like air operated chucks for holding , large work-pieces quickly.

In the case of a capstan lathe, the cross slide is mounted on a carriage which rests on the bedways between head stock and the ram. The carriages rests on both the front and rear ways on the top of the bed. Some turret lathe are equips with side hung type carriage. The carriage of this type does not require support from the rear bedways but slides on the top and bottom guideways provided at the front of the lathe. This construction enables larger diameter of work to be swung above the lathe bedways. There is no rear tool post on this type of machine as the carriage does not extend upto rear bedways.

Turret Indexing mechanism1. Hexagonal turret, 2. Index plate, 3. Bevel gear 4. Indexing ratchet, 5.Turret spindle. 6. Bevel Pinion, 7.

Indexing Pawl, 8. Screw stop rods, 9.Lathebed. 10. Plunger actuating tont, 11. Pinion shaft,12 Stop, 13. Plunger Pin 14. Plunger,15. Plunger Spring

The plunger 14 fitted within the housing and mounted on the saddle locks the index plate by spring pressure 15 and prevents any rotary movement of the turret as the tool feeds into the work.

A pin 13 fitted on the plunger 14 projects out of the housing.

An actuating cam 10 and indexing pawl 7 are attached to the lathe bed 9 at the desired position.

Both the cam and the pawl are spring loaded.

As the turret reaches the backward position , the actuating cam 10 lifts the plunger 14 out of the groove in the index plate due to the riding of the pin 13 on the beveled surface of the

cam 10 and thus unlocks the index plate 2.

The spring loaded pawl 7 which by this time engages with a groove on the ratchet plate 4 causes the turret to rotate as the turret head moves backward.

When the index plate or the turret rotates through one sixth of revolution, the pin 13 and plunger 14 drops out of cam 10 and the plunger locks the index plate at the next groove.

The turret is thus index by one sixth of revolution and again locked into the new position automatically.

The turret holding the next tool is now fed forward and the pawl is released from the ratchet plate by the spring pressure.

The synchronized movement of the stop rods with the indexing of the turret can also be understood from the figure above.

The bevel pinion 6 meshes with bevel gear 3 mounted on the turret spindle.

The extension of the pinion shaft carries a plate holding six adjustable stops rods 8.

As the turret rotates through one sixth of revolution the bevel gear 3 caused the plate to rotate.

The ratio of the teeth between the pinion and gear are so chosen that when the tool mounted on the face of the turret is indexed to bring it to the cutting position, the particular stop rod for controlling the longitudinal travel of the tool is aligned with stop 12

The setting of the stop rods 8 for limiting the feed of each operation may be adjusted by unscrewing the lock nuts and rotating the stop rods on the plate.

Thus six stop rods may be adjusted for controlling the longitudinal travel a the tools mounted on the six faces of the turret.

Principal parts of capstan and turret lathes

The turret has essentially the same parts as the engine lathe except the turret and the complex

mechanism incorporated in it for making it suitable for mass production work.

Different parts of capstan lathe are:

Head stock, Saddle for cross-slide. Cross-slide tool post, Hexagonal turret, Saddle for

auxiliary slide, Auxiliary slide, Lathe head, Feed rod, Cross-slide tool post,

Different parts of turret lathe are:

Hexagonal turret, Head stock, Cross-slide tool post, Feed rod Turret saddle, Saddle for cross-slide..

Bed:

The bed is a long box like casting provided with accurate guide ways upon which are

mounted the carriage and turret saddle. The bed is designed to ensure strength, rigidity and

permanency of alignment under heavy duty services. Like engine lathe precision surface finishing

methods must be applied to keep it resistant to wear during service period.

Headstock:

The headstock is a large casting located at the left hand end of the bed. The headstock of

capstan and turret lathe may be of the following types:

(i) Step cone pulley driven headstock

(i) Direct electric motor driven headstock

(ii) A l l gea r ed heads tock

(iii) Pre obtive or pre selective headstock.

Step cone pulley driven headstock:

This is the simplest type of headstock and is fitted with small capstan lathes where the lathe

is engaged in machining small and constant diameter work pieces. Three or four steps of pulleys can

cater to the needs of the machine.

Direct electric motor driven headstock:

In this type of headstock the spindle of the machine and the armature shaft are one and the same.

Any speed variation or reversal is effected by simply controlling the motor. The machine is suitable

for smaller diameter of work pieces rotated at high speeds.

All geared headstock:

On the larger lathes, the headstocks are geared and different mechanisms are

employed for sped changing by actuating levers. The speed changing may be affected without

stopping the machine.

Pre optive or pre selective headstock:

It is an all geared headstock with provisions for rapid stopping, starting and speed

changing for different operations by simply pushing a button or pulling a lever.

Different speeds are required for different operations. These speed variations are obtained by

placing the speed changing lever in the required position.

After the first operation is complete, a button or lever is simply actuated and the spindle

starts rotating at the selected speed required for the second operation without stopping the

machine.

CROSS-SLIDE & SADDLE.

In small size capstan lathes, hand operated cross-slide and saddle are used which are

clamped 'on the lathe bed at the required position. The larger capstan lathes and heavy duty

turret lathes equipped with usually two designs of carriage

(i) Conventional type carriage (ii) Side hung type carriage

Conventional type carriage bridges the gap between the front and rear bed ways and is equipped with four station type tool post at the front, and one rear tool post at the back of the cross-slide.

The side hung type carriage is generally fitted with heavy duty turret lathes where the saddle rides on the top and bottom guide ways on the front of the lathe bed

The design facilitates swinging of larger diameter of work pieces without being interfered by the cross slide. The saddle and the cross slide may be fed longitudinally or crosswise by hand or power.

The tools are mounted on the tool post and correct heights are adjusted by using rocking or packing pieces.

THE TURRET SADDLE AND AUXILLARY SLIDE.

In a capstan lathe, the turret saddle bridges the gap between two bed ways, and the top face is

accurately machined to provide bearing surface for the auxiliary slide.

The saddle may be adjusted on the lathe bed ways and clamped at required position. In a turret lathe the turret is directly mounted on the top of the saddle and any movement of the turret is effected by the movement of the saddle. The turret is the hexagonal tool holder intended for holding six or more tools. The centre line of the each

hole is perfectly aligned with the ax is of the lathe when aligned with the head stock spindle.

In addition to these holes, there are four tapped holes on each face of the turret for securing different

tool holding attachments. After one operation is completed, as the turret is brought back away from the

spindle nose, the turret index automatically by a mechanism incorporated on the bed and in turret saddle,

so that the tool mounted on the next face is aligned with the work.

CAPSTAN AND TURRET LATHE MECHANISM:The carriage, cross-slide, turret-slide, and the saddle holding the turret may be fed, in to the work by hand or power.

They are two main mechanisms

I. Turret indexing mechanism 2. Bar feeding mechanism

TURRET INDEXING MECHANISM:

A simple line sketch of the mechanism is show in figure

The turret 1 is mounted on the spindle 5, which rests on a bearing on the turret saddle. 1. The index plate 2, the bevel gear 3 and an indexing ratchet 4 are keyed to the spindle 5. The plunger 14 fitted with in the housing and mounted on the saddle locks the index plate by spring 15 pressure and prevents any rotary movement of the turret as the tool feeds in to the work.A pin 13 is fitted on the plunger 14 projects out of the housing. An actuating cam 10 and the indexing pawl 7

are attached to the lathe bed 9 at the desired position.

Both the cam and the pawl are spring loaded. As the turret reaches the backward position, the actuating carn10

lifts the plunger 14 out of the groove in the index plate due to the riding of the pin 13on the beveled surface

of the cam 10 and thus unlocks the index plate2.

The spring loaded pawl 7 which by this time engages with a groove of the ratchet plate 4, causes the ratchet to

rotate as the turret head moves backward.

When the index plate or the turret rotates through one sixth of revolution, the pin 13 and the plunger 14 drops

out of the cam 10 and the plunger locks the index plate at the next groove. The turret is thus indexed by one

sixth of revolution and again locked in to the new position automatically.

B A R F E E D I N G M E C H A N I S M :

Capstan and turret lathes while working on bar work require seine feeding mechanism for bar feeding. a simple bar feeding mechanism is illustrated as show in figure.

The bar 6 is passed through the bar chuck 3, spindle of the machine and then through the collet chuck.

The bar chuck 3 rotates in the sliding bracket body 2 which is mounted On a long slide bar. The bar chucks 3 grips the bar centrally by two set screws 5 and rotates with the bar in the sliding bracket body 2.

One end of the chain 8 is connected to the pin 9 fitted on the sliding bracket 10 and the other end supports a weight 4, the chain running over two fixed pulleys 7 and 11 mounted on the slide bar.

The weight 4 constantly exerts end thrust on the bar chuck while it revolves on the sliding bracket and forces the bar through the spindle, the moment the Collet chuck is released.

Thus the feeding may be accomplished without stopping the machine.

CAPSTAN AND TURRET LATHE SIZE

The size of a capstan or turret lathe is designated by the maximum diameter of rod that

can be passed through the head stock spindle and the swing diameter of the work that can be rotated

over the lathe bed ways. In order to specify the lathe fully, other important particulars such as

number of spindle speeds, number of feeds available to the carriage and turret saddle, net weight of

the machine, floor space and power required, etc. should also be stated.

WORK HOLDING DEVICES:

The standard practice of holding work between two centers in an engine lathe finds no

place in a capstan or turret lathe as there is dead centre to support the work at the other end. Work

is, therefore supported at the spindle end by the help of chucks and fixtures. The usual methods of

holding work in a capstan or turret lathe are

Jaw chucks,

Self centering chuck, Combination chuck, Independent chuck, Air operated chuck

Collet chucksPush out type, Dead length type, Draw in type

COLLET CHUCKS:

The collet chucks are used for gripping bars introduced through the head stick spindle of a

capstan or turret lathe and is one of the most common method of holding work.

Different sizes of spring collets having square, hexagonal, round or any other shaped bore

are fitted in the chuck body for holding different sizes of bar having different sections.

PUSH OUT TYPE:

To grip the work, the tapped portion of the spring collet is pushed in to the mating

taper of the chuck. There is a tendency of the bar to be pushed slightly outward when the collet is

pushed in to the chuck body for gripping, lithe bar is fed against a stop bar fitted on the turret head,

this slight outward movement of the bar ensures accurate setting of the length for machining.

DRAW IN TYPE:

To grip the work, the tapered portion of the spring collet is pulled back in to the mating

taper of the chuck which causes the split end of the collet to close in and grip the bar. The

machining length of the bar in this type of chuck cannot be accurately set as the collet while

closing will draw the bar slightly outward towards the spindle.

DEAD LENGTH TYPE:

For accurate positioning of the bar, both the push out and draw in type collet present some

error due to the movement of the bar along with the collet while gripping. This difficulty is

removed by using a stationary collet on the bar. A sliding sleeve closes up on the taPeCE4 collet.

which is prevented from any end movement-by the shoulder stop.

FIXTURE:

A fixture may be described as a special chuck built for the purpose of holding, locating

and machining a large number of identical pieces which cannot be easily held by conventional

gripping devices. Fixtures also serve the purpose of accurately locating the machining surface. The

main functions of a fixture are as follows

They accurately locate the work

(ii) They grip the work properly, preventing it from bending or slipping during

machining operations.

(iii) They permit rapid loading and unloading of work pieces.

MILLING MACHINE

Introduction

Milling machine is the process of removing metal by a rotating multipoint cutter. The work is fed past the cutter. The metal is removed in the form of small chips. Multipoint cutter is used to removal is very fast. It produces a good surfaces finish and accuracy is also high.

Principle of milling (cutting): -

In milling the cutter has a rotary movement, the speed of which depends upon the cutting speed required. Driving the Milling arbor at various rotational speeds makes it possible to achieve approximately the same cutting speeds [peripheral cutter] with cutters of different diameters.

While the milling cutter rotates at a high speed, and because of the multiple points, it removes at a very fast rate, in comparison with other machine tools.

By milling machine we can produce flat (horizontal, vertical, angular) and formed surfaces. An milling machine finds wide application in production work as the machine can hold one or more number of cutters at a time, and is good in accuracy, surface finish etc..,

Classification: -

The classification according to the general design of the milling machine is:

a) Column and Knee Type,

a. Plain milling machine

b. Universal milling machine

c. Omniversal milling machine

d. Vertical milling machine

b) Fixed Bed Type

e) Plano Miller

d) Special Type

a. Rotary table milling machine

b. Drum type milling machine

c. Planetary milling machine

d. Pantograph milling machinePla in Mi l l ing Mach ine : -

Plain milling machine is also known as hor izonta l mi l l ing machine , s ince the spindle of the machine is horizontal.

There is a vertical column on the base. The column houses the main drive and the spindle. The column as vertical dovetail guide ways on its front face. The knee can move vertically on these guide ways. This is done by rotating the elevating screw.

Universal Milling Machine: -

Universal mil l ing machine is similar in

all respects to the horizontal plain milling machine

except for table. The table is mounted on swivel

base. The swivel base has not degree graduations.

The knee at its top has horizontal dove tail guide ways perpendicular to the front face

of the column. The saddle can slide on these guide ways away from the column or towards

t h e c o l u m n . T h e t o p o f t h e s a d d l e h a s horizontal guide ways parallel to the face of

the column. The table travels longitudinally along these guide ways. The longitudinal

travel of the table is perpendicular to the axis of the spindle.

T h e t o p s u r f a c e o f t h e t a b l e i ' s accurately machined. There are T-slots along

the length of the table for holding the work.

T h e v e r t i c a l m o v e m e n t o f k n e e ,

crosswise movement of the saddle and the

longitudinal movement of the table can be

o b t a i n e d b y h a n d o r p o w e r . T h e k n e e

houses feeding mechanism.

The spindle of the machine is located in the

upper part of the column. It is rotated by an electric

motor through belts and gear.

The front end of the spindle is called nose.

The nose just projects from the column face. It has

tapered hole. Arbors or various cutting tools can

be inserted into this hole.

There is an over arm mounted on the top of the column. It acts support for the arbor.

The over arm supports the arbor by means of yokeThe table can be swivelled about a vertical axis. It can be swivelled up to a maximum of 450 on the

either side of the normal position.

Thus the universal milling machine table has the following movement:

1. Vertical movement — through the knee.

2. Cross wise movement — through the saddle.

3. Longitudinal movement of the table.

4. Angular movement of the table — by swivelling the table on the swivel base.

By swivelling the table, the work can be fed at an angle to spindle axis. This is used in helical milling operations.

Special attachments like dividing

D451 need vertical milling attachment, and , rotary table attachment are used in the universal milling machines. Using these attachments, the machine can produce spur gear, bevel gear, twist drill and reamers.

Vertical Milling Machine: -In a vertical milling machine, the spindle is vertical. The table may be plain type of universal type. The vertical column is mounted on the base. The front face of the column has vertical guide ways. The knee

moves on these vertical guide ways. The knee has horizontal guide ways on its top surface.

cot

Swint Dose

Ante

Alt-Universal Milling

Machine

The saddle can move cross wise on these guide ways perpendicular to the spindle axis (i.e.) away

from the column or towards the column. The saddle has guides ways on its top.

The table can move longitudinally along these guide ways. This movement is perpendicular to the

spindle axis.The spindle is mounted on top of the column. The spindle has swivel base. So the head can be titled at an angle. This permits machining of angular surfaces. In

some machines, the spindle can be adjusted up or down. The vertical movement of the knee, cross wise

movement of the saddle, and the longitudinal movement of the table can be obtained by hand or power. The knee houses the feeding mechanism. This machine is used for machining grooves, slots and flat surfaces. End milling cutters and face milling cutters are generally used in vertical milling machine.

Specification of Milling Machine

1. The table length and width 1120 x 280 mm

2. Number of spindle speeds and feeds 6

1. Floor space 6 x 5 feet

1. Net weight 2000 kg

3. Power of driving motor 3 H.P

4. Max. longitudinal travel, Cross travel &

Vertical travel of the table 558 x 229 x 406 mm

7. Type of Milling Machine Coloumn and Knee type

Work holding devices: -

The following work holding devices are used in milling machine.

1. Plain vice 4. Indexing head

2. Universal vice 5. Milling fixture

3. Swivel vice

Tool holding devices: -

The different tool holding devices used in milling machine are

1 . A r b o r s

a) Standard arbor b) Stub arbor

2 . Adapters 3. Spring collets

Milling cutters: -

The following milling cutters are commonly used in milling

1. Plain milling cutter 6. Angle milling cutter

2. Stab milling cutter 7. T-slot milling cutter

3. Sitting saw 8. Fly cutter

4. Side milling cutter 9. Form cutter

5. End milling cutter 10. Woodruff key slot milling cutter

Milling Processes

1. Up Milling: -

It is also called conventional

milling. Metal is removed when the

cutter teeth move upwards. Here the

cutter rotates opposite to the direction of feed of work piece. In up milling, the chip thickness is

minimum of the beginning of the cut. It reaches the maximum at the end of the cut. So the

stress on the teeth is minimum at the end of the beginning of the cut. The stress increases

gradually and is maximum at the end of the cut.. The cutting action of the teeth is upwards. So it

will try to lift the work piece form the vise. The machined surface is not very smooth. Applying

the coolant at the cutting edge is difficult. The -chips accumulate in front of the cutter at the

cutting zone. So chip removal is difficult chips interfere with the cutting action.

2. Down Milling: -

It is also called climb milling. Metal is removed when the cutter teeth move downwards.

Here the cutter rotates same direction as the feed for work piece. In down milling, the chip thickness

is maximum of the beginning of the cut. The chip decrease to the minimum at the end of the cut

Here the maximum stress acts on the teeth at the beginning of the cut. This gives shock lot

to the teeth, the cutting action of the teeth presses the work piece downwards. This helps

clamping of the work pieces. Down milling will give better surface finish. Coolant can be

effectively applied on the cutting edge. The chips accumulate at the back of the cutter away

from the cutting zone. So chip removal easy. Chips do not interfere with the cutting action.

dle

Dividing Heads: -

The following types of dividing heads are generally used.

1. Plain simple dividing head. 2. Universal dividing head.

What is meant by indexing?

It is an operation of dividing the circumference of a work piece into equally spaced divisions

for milling gears, splines, squares, cutting of flutes in reamers etc.,

The indexing head is also used to rotates the work piece at a predetermined ratio to the table

feed rate to produce cams, helical grooves etc..,

This operation is performed on a milling machine by means of an indexing attachment is called

as indexing head or the dividing head.

Gear Manufacturing: -

Gears are toothed wheels used for transmission of power or motion. There are different

types of gears used in industry. They are:

a)Spur gears are cylindrical discs on which gear teeth are cut on the periphery. The teeth are

parallel to the axis. These gears are used to transmit motion along parallel axes.

b) Helical geom.-the teeth are cut at an angle to the axis. This angle is called helix angle, helical

gears run smoothly without noise.

c)Rack and pinion gears are used to convert rotary motion into linear motion or vice versa.

Rotary motion of the pinion is convened into linear motion in the rack.

d) Worm and worm wheel are used to get heavy redaction in speed. Here the axes are

perpendicular to each other.

e)Bevel gears are used to transmit motion form one gear to another gear with their axes

inclined to one another. A set of mitre bevel gears have equal number of teeth and their axes

are at right angles to each other.

Methods of Indexing: -

The following are the different methods of indexing:

1. Direct or rapid indexing 3. Differential indexing2. Plain or simple indexing 4. Angular indexing

Plain (or) Simple Indexing: -This indexing method is used for Locking pin Body-Spindle

work divisions that could not be indexed by direct or rapid indexing. The universal dividing head is used for indexing. The dividing head spindle is rotated by turning the index crank.

One complete turn of the index crank will

make the spindle PlelfrPiY40§Iglall revolution.

This is so because, the single threaded worm drives the 40 teeth worm wheel which is

headed to the spindle. For indexing a fraction of turn, an index plates having the suitable

hole circle can be used.

The hole circ16available in standard index plates are given below:

Spur Gear Milling Procedure & Gear Calculations: -

I. Calculation of gear tooth proportions

2. Indexing calculations

3. Setting the dividing head & tail stock on machine table, mounting gear blank

4. Selection of cutter & centering of the gear blank with the cutter

5. Setting suitable cutting speed & feed and taking the cut

6. Inspection of tooth profile

The Various Elements of a Spur Gear are illustrated.Spur gear proportions as per BIS in terms of module (m) and number of teeth (Z) are

given below: pressure angle 's 20°

S. No Name of tooth Gear tooth S. No Name of tooth Gear tooth

1. Pitch diameter Z m 2. Outside diameter (Z + 2) m

3. Addendum m 4, Tooth thickness 1.5708 in

5. Duodenum 1.25 in 6. Clearance 0.25 m

7. Working depth 2 in 8. Circular pitch IT m

9. Tooth depth 2.25 m 10. Radius of fillet 0.4 m to 0.45

Plate no 1 : 15, 16, 17, 18, 19 and 20

Plate no 2 : 21, 23, 27, 29, 31 and 33

Plate no 3 : 37, 39, 41, 43, 47 and 49

Some index plate have hole circles on both sides as given below:

worm heel 40 teetharbor or work piece

index Plate "ndex crank

First side :18,19, 21, 24, 29, 35 and 39

Second side : 19,20, 26, 31, 35 and 40

Single st worm

worm shaft sector arm

PITCH CIRCLEHelical gear milling procedure & gear calculations: -

I. Calculation of blank diameter-and gear tooth details

2. Arrangement of indexing

3. Selection of cutter & centering it over the blank

4. Setting the table

5. Selection of change gears

6. Determination of speed, feed and depth of cut. Helical gear proportions as per BIS in terms of normal module (Mn) and number of teeth (Z) are given below. Pressure angle is 200

.

S. No Name of tooth element Gear tooth proportions

1. Pitch diameter Z m

2. Addendum Mn

3. Duodenum 1.25 Mn

4. Tooth depth 2.25 Mn

5. Outside diameter Z m + 2 Mn

6. Normal Tooth thickness 1.5708 Mn

Where: - Normal module (Mn) = m cos a

module and a helix angleMILLING OPERATIONS: -

I. Plain Milling

2. Form Mill ing

3. Face Milling

7. Straddle Milling

8. Gang Milling

'ACE VIOTOOTH THICKNESS ACRE WOW I 0 A s € O R a E

OUT SLOE ORK DSC NOVO CIRCLET

Pam CIRCLE - CIRCLE

NE OF ACTION TARGE ILO_ LIL CIRCLE

PRESSURE

PEITPENDICTIARTO CENTK LIVE

PITICHICITUE

CASE

PROLE

CENTRE TM

\ —ROOT VALLE

CILIA

Llf1OTTONL ALIO

Pressure angle

4. Side Mill ing

5. End Mill ing

6. T — 'Slot Milling

Expt. No: KEY WAY MILLING Date: -

Aim: - To mill a key way on the given work piece using end mill cutter

Tools required: -

End milling cutter, 'V' block, strap clamp, height gauge, brush, vernier caliper, and scriber. Materials required: - A

cylindrical work piece of diameter ...min and length ...mm of mild steel rod.

Procedure: -

a) The work piece on to which key way is to be cut punch marked for the dimension.

b) The work is placed and a drill operation say 5-10 mm is done to allow end clearance to milling cutter.

c) Work is liked on milling machine table.

d) End milling cutter is used to cut key way.

e) Start the machine and run at required speed.

1) Depth of cut is given manually by raising table through knee elevating screw.

g) Feed is given manually by rotating hand wheel.

h) Coolant oil (SAW — 20W140) is applied on the cutting area of the work piece to lubricate and carry away heat.

i) Repeat the procedure to the required depth.

j) C a u t i o n : F e e d u n i f o r m l y .

Result: - Thus a key way is milled on given work piece.

All dimensions are in mm.

Spur Gear Forming Using Universal Milling MachineExpt No: - Date: -

Aim: - To form a spur gear on the gear blank using universal milling machine

Tools required: -

H.S.S turning tool, Drill bit, Revolving center, Milling cutter, Vernier caliper, Adjustable spanner, Tool post key,

Chuck key, Micrometer dot punch, hammer, mandrel, etc...

Materials required: - A cylindrical work piece of diameter ...mm and length ...mm of cast iron rod.

Operation sequence: - Facing, Plain turning, ,Chamfering, Drilling are using lathe machine and spur gear forming

operation by milling machine.

Observatiott:' -

Milling machine:Pitch distance moved by the slide for one full rotationL.0 for vertical feed slide —

Calculation for spur gear parameter: -

S. No Name of tooth element Gear tooth proportions

1. Pitch diameter Z m

2. Addendum m

3. Dedendum 1.25m

4. Working depth 2 m

5. Tooth depth 2.25 m

6. Outside diameter (Z + 2) m

7. Tooth thickness 1.5708 m

8 Clearance 0.25 m

9. Circular pitch it M

9. Radius of fillet 0.4 m to 0.45 m

Calculation for simple indexing: -

Indexing crank movement = No. of holes in index plate / No. of divisions required = 40 / N

Where: N (Z) number of divisions or sides required

Example: I.C.M = 40 / N = 40/20= 2

Hence index crank pin is inserted in every 2" hole of the 18" hole circle

No.of graduations on the micrometer

Procedure: -

I. The dimensions of the given work piece is measured by Vernier caliper.

2. Correct the length and diameter of the work piece to the given dimensions by facing and turning operations by using

lathe machine.

3. Perform the chamfering operation in order to avoid the shaper edges.

4. Fix the drill bit in the tailstock sleeve and do the drilling operation for the entire length of the work piece.

5. Do the turning operation to bring the diameter to------------------mm.

6. Remove the job from the chuck and it is mounted in the mandrel. The mandrel is held on the chuck and the other

end is supported by the revolving center.

7. Depending' upon the number of teeth to be cut and the module required on the gear blank, the corresponding gear

cutter is selected and fixed in the arbor of the milling machine.

8. Position the lever to obtain the required spindle speed depending upon the diameter of the work piece.

9. Position the cutter with respect to the cutter of the work piece. This is done by moving the vertical feed lead screw and

the cross feed lead screw handle.

10. Do the skins cut by touching the top surface of the work with the plain milling cutter? This is done by placing the

wet paper on the top surface of the gear blank and the work piece is lifted against the rotating cutter.

The movement when the cutter touches the paper, it makes the paper to slide away. This indicates that cutter is having

surface contact with the gear blank. Now adjust the micrometer dial of the vertical feed lead screw to zero.

11. Lower the table and by rotating the longitudinal slide hand wheel, the work piece is made from the cutter.

12. Set the depth of cut by raising the table and the tooth spaced is formed by moving the work piece against the

rotating cutter.(Note: - The depth of cut is given in several steps)

13. Remaining tooth is formed by indexing the work piece (N-1) number of items.

14. The above two steps are repeated till the required depth of------------------------- mm is given in the

vertical feed slide.

WORK SHEET FOR CALCULATION

MILL A 20 TEETH SPUR GEAR OF PROPER POROPORTIONS

Result: -

Thus the spur gear operation is performed inmm module on the given work piece.

--Coning

T W O d e

NOWNCIAtURE OF PLAIN 11ILLING cLIME

INTRODUCTION TO GRINDING PROCESS

Grinding Machines

Grinding is a metal cutting operation by a rotating abrasive wheel. By grinding, verygood surface finish is obtained on the work piece.

High dimensional accuracy is obtained in the work piece. Mostly grinding is used as a

finishing operation.

Very hard surfaces can be finished in grinding.

Grinding wheel is made of small abrasive particles held together by a

bonding material. The abrasive particles are very hard. These hard abrasive particles or

grains project „ on the surface of the wheel. The abrasive particles form multiple cutting edges. While grinding, the

wheel is rotated and the work is fed against the wheel. The abrasive particles move with high velocity and shear of

small metal particles from the work piece. While machining, the blunt abrasive grains will be released from the wheel

surfaces. In their place, new abrasive grains project from the surface of the wheel. This is called the self sharpening of

the grinding wheel.

Classification of grinding machines: -

The grinding machines are classified as follows:

1. Rough Grinders:

Floor stand grinders • Abrasive belt grinders

Bench grinders • Swing frame grinders

Portable grinders

2. Precision Grinders

Cylindrical grinders • Centre type universal grinders

Centre type plain grinders • Centre less grinders

3. Internal Grinders

Chucking type grinders • Centre less grinders

Planetary type grinders

4. Surface Grinders

R e c i p r o c a t i n g t a b l e - H o r i z o n t a l 4• Rotary table - Vertical spindle

spindle

Rotary table - Horizontal spindle

Reciprocating table - Vertical spindleSurface Grinder Machine

Surface grinders are mainly used to grind fiat and plane surfaces. They arc also used to grind to irregular, curved,

tapered and other formed surfaces.

Machine guide ways, piston rings, valves, dies, surface plate etc are some the pads which are finished by surface

grinding.

SADDLE

SADDLE CROSS FEED HANDLESADDLE FEEDSADDLE SPEED CHANGEADJUSTING SADDLE HYDRAULICLEVER SYSTEM START PUSH

BUTTON

BASE

Horizontal Spindle Reciprocating 'fiber Surface Grinder

Base: - The base is a rectangular boxlike casting. It houses the driving

mechanism inside. It has a vertical column mounted at the back. The base

has machined horizontal guide ways at the top. The guide ways are

perpendicular to the column.

9 Saddle: - The saddle is mounted over the base. It can move along with

guide ways on the perpendicular to the column. This gives cross feed to the

work.

•l• Table: - The table slides on the horizontal guides on the saddle.

This movement is parallel to the face of the column. This gives the

longitudinal feed to the work. There are T-slots on the top of the table

for clamping work piece or fixtures.

Wheel Head: - The wheel head is mounted on the column. It has an

independent motor for driving the wheel. The wheel head can slide up and

down along the vertical guide ways of the column. This vertical adjustment of the wheel head is done manually. This is to

accommodate the work piece of different heights and to give depth of cut.

Operation: - The work piece clamped on the table reciprocates under the rotating grinding wheel. The work piece

may be held by means of a magnetic chuck or fixture. Trip dogs at the side of the table are adjusted for getting the correct

stroke length for the table. The periphery of the grinding wheel does the grinding. Cross feed is given to the work piece after

every stroke. After the full width of work piece is ground, the wheel head is lowered downwards to give depth of cut.

Cylindrical Grinder: -

A plain centre type cylindrical grinder, the main parts of grinder are:;Nark Piece

4 Base or bedGrinding Wheel

Tables Head StockTail Stock

Head stock and tail stock

Wheel head

STOP LEVEL OPERATION BOARD

Base or bed:

The base or bed rests on the floor and supports all the other parts. It is of box like construction. It houses table

drive mechanism. On the top of the bed there are length wise machined guide ways.

T a b l e s :

There are two tables — lower and upper table. The lower table slides over the guide ways of the bed. This

sliding movement gives the traverse feed or longitudinal feed to the work piece. This movement can be obtained by

hand or power. Adjustable trip dogs are clamped in the longitudinal slots at the side of the lower table. These trip

dogs actuate the table reversing lever. Thus the reciprocating movement for the table is obtained. The upper table is

pivoted over the lower table. A maximum angle of swivel is 100 on either side. The swiveling is used for grinding tapers.

The upper table has length wise T-slots for fitting the head stock and tail stock.

4• Head stock and Tail stock:

The head stock and tail stock are mounted on the upper table. They have centers. The work piece is held between the

head stock and tail stock.

The work piece is driven b y the head stock through dog and driving pin. The tail stock can be adjusted a clamped in

various position. This is to hold different lengths of the work piece. Work piece can also be held using a chuck in the head

stock.

4• Wheel head

The wheel head carries a grinding wheel and the wheel driving motor. The wheel head is placed over the bed at its

back side. The wheel head is mounted on a slide. It can be moved perpendicular to the table guide ways. This movement is the

cross feed. This cross feed can be given either by hand or power.

Centre type universal grinder:

GrhelhgWheelHeed

StocToil Stock

Wheel Heed

ei Table cLower Table —

Universal Grinder Has The Following Additional Features:

I. The centre of the head stock spindle can be used live or dead. The work can be held and revolved by a chuck. It can also

be held between centers and revolved.

2. The wheel head can be swiveled in a horizontal plane in any angle The wheel head can be fed in the inclined

direction also.

3. The head stock can be swiveled to any angle in the horizontal plane.

4. There is an auxiliary wheel head for doing internal grinding.

Grinding wheel: - Grinding wheels are made up of small abrasive particles held in together by bonding material.

Abrasives: - Abrasives are held substances which are used as cutting edges in the grinding wheel. Small abrasive

particles are used in grinding wheels. They are called abrasive grains. There are two types' abrasives: (i) Natural

abrasives and (ii) Artificial abrasives.

Bonds: - Bond is an adhesive used to hold abrasive grains together in the grinding wheel. The following

are the various types of bonds used.

Grinding allowance: - Machine parts are processed in different machines such as lathes, milling machines,

shaping machines, etc.., in such a way that their final dimensions have some stock left, which is finished during

the grinding operation. The amount of this stock left is called the 'grinding allowance'. No definite value of the

grinding allowance can be given as a general rule because this depends upon too many variable factors. In

general it varies from 0.2mm to 0.5 mm. The grinding allowance is given in microns. Closely spaced, fine

abrasive grinding wheels generally give better finishes than coarse ground, widely-spaced abrasive wheels, and

hence less grinding allowance may be sufficient. Keeping more grinding, allowance than necessary ultimately increases

the cost of the grinding operation.

Identifying Grinding Wheels

> Standard Marking System for Aluminum-Oxide and Silicon-Carbide Bonded Abrasives


Expt. No: - Surface Grinding Date: -

Aim: - To grind a plane surfaces (M.S fiat work piece) to the required dimensions using surface grinding

machine.

Tools required:- Vernier caliper, Adjustable spanner, Micrometer, dot punch, hammer, diamond wheel

dresser, try square, etc..,

Materials required: - A Rectangular work piece mm, length rum and thickness Observation: -

L. C for vertical feed slide

No.of graduations on the micrometer 50Procedure: -

I. The dimension on the given work piece is checked with the micrometer and Vennei. Caliper. The work

piece is fixed rigidly in the bench vise and the sides are filled with the help of flat file to bring the sides of the flat

pieces to 90°.

2. The flat piece is placed on the surface grinding machine magnetic table and t he magnet is activated by turning

the lever.

3. The work piece is made to touch the grinding wheel. This is done by raising the table against the rotating

grinding wheel.

4. The gaduation is set to zero in the micrometer of the vertical slide.

5. A depth of cut is 0.1min is given by rotating the hand wheel of vertical slide and the work piece is fed against

the rotating wheel to and fro.

6. Simultaneously give the cross wise feed movement to the table, to grind the entire width of the workpiece.

Coolant can be used to cool the work and protect its surface.

Result: - The flat surface grinding operation is done by surface grinder.

Expt. No: - Cylindrical Grinding Date: -

Aim: - To grind the external surface of a cylindrical work piece on a cylindrical grinding machine.

Tools required:- Vernier caliper, Adjustable spanner, Micrometer, dot punch, hammer, diamond wheel dresser, try

square, flat file, centre bit, H.S.S cutting tool, etc.., _

Materials required: - A cylindrical work piece of diameter is...mm, length _ram of mild steel.

Observation. -Pitch distance moved by the slide for one full rotation _ 0.1

Pitch distance moved by the slide for one full rotation

1.25

Grinding 'wheel

Doplh ol cul

Wockplaco on Wilk

- - - CLononodinol feed

Fowl view

L.0 for feed lead screw —No.of graduations on the micrometer 20

Procedure:

1. Hold the work piece in the three jaws and do the facing operation in order to correct the length to ..-... mm.

2. Do the centre drilling operation on the end face in order to hold the work piece in between the centers.

3. Do the turning operation to reduce the diameter to .... mm for a length is .... mm.4. Do the step turning operation to bring the diameter to ... ram for a length .... mm.

5. Remove the work piece from the chuck, apply grease to the center drilled holes and hold the work piece in between

centers of the cylindrical grinding machine.

6. Give the depth of cut by moving the cross feed lead screw. The depth of cut should not exceed ... mm.

7. Set the trip dogs for given grinding length in order to control the longitudinal feed movement.

8. Switch ON the machine, grinding wheel, coolant and longitudinal feed movement motor.

9. The longitudinal feed movement motor driver the table and it reverse after being hit by the stop dog.

10. The depth of cut is given gradually till the required dimension of ....mm is obtained.

11. Finally check the dimensions of the work piece with the micrometer.

Result: - Thus the grinding operation is performed on the turned work piece using cylindrical grinding machine.



Gear Hobbing MachineHobbing is a process of generating a gear by means of a rotating cutter called hob. The hob has helical

threads. Grooves are cut in the threads parallel to the axes. This will provide the cutting edges. Proper rake and

clearance angles are ground on these cutting edges. The rotating hob acts like a continuously moving rack as its cuts.

The gear blank is mounted on a vertical arbor. The hob is mounted in a fotating arbor. The hob axis is tilted

through the hob lead angle 'a' so that its teeth parallel to the axis of the gear blank.

Then 'a' = (90° — a))

Where a i helix angle of the hob thread.

The hob axis cs inclined at 'a' with the horizontal as shown in fig.PCCO(Note: hob lead angle = 900 — hob helix angle) Or MOS

The hob is rotated at suitable cutting speed. h is fed across the blank face. The

hob and blank are made to rotate in correct relation ship to each other i.e., they

rotate like a worm and worm gear in mesh. For one rotation of the hob, the

blank rotates by one tooth. (hi case of single start hob.) For cutting helical

gears, the axis of the hob is inclined to horizontal by 'a' Where

a 0 + (90°— a )) (if the helix of the hob and the helix of the gear to be cut are

different i.e., one is right handed and another is left handed)

a 0 - (90° — a 0 (if the helix of the hob and the helix of the gear to be cut are

both right handed or both left handed)

Where: - a I — Helix angle of the hob

0— Helix angle of the helical gear to be cut

Application: - Hobbing is used for generating spur, helical and worm gears.

Limitations: -

(i) Internal gears cannot be generated.

(ii) fobbing cannot be used for producing gear teeth. Hence high rate of to shoulders

Hobbing is a process of generating a gear by means of a rotating cutter called hob.

S.- The hob has helical threads.

Grooves are cut in the threads parallel to the axis.

This will provide the cutting edges.

Proper rake and clearance angles are ground on these cutting edges.

The rotating hob acts like a continuously moving rack as it cuts.

Schematic representation of gear trains in a gear hobbing mic.

arrangement

(90 — HEW ANGLE OF HOB)Frzeo

OF HOB

ARBOR

R BLANK

HOB

Gar

— )

ir re

Cutter/

Soca sib. Wier Positions

NOM Genorded

Generation of involutes profile

-Advantages: -

1. A single hob with the given modulo can be used for generating gear with any number of teeth of the same module.

2. The same hob can be used for spur and helical gears

3. Operation is continuous. So very fast of production.

4. Perfect tooth space is obtained.

5. Process is automatic and so less skilled operator is sufficient.

6. Worm gears are generated only hobbing.

7. Multiple blanks tan be cut-at-a time, Hence high rate of production.

Setting the Angle of Rob Slide for Cutting Spur Gear: - The slide is rotated the clockwise. (The fly wheel mover

downward through an angle equal to the helix angle of hob) -

For Right Hand Helical Gear: - The slide is rotated the rough and equal to the difference of helix angle of gear and helix

angle of hob in anti-clockwise direction. (The fly wheel going upward)

For Left Hand Helical Gear: - The slide is rotated through an angle to the sum of helix angle of gear and helix

angle of hob. (The fly wheel moving downward)

After setting the angle of hob slide the slide is clamped by means of four bolts provided. Formula for gears:

1-Jobbing is used for generating Spur, Helical and Worm Gears.

INo. of Teeth l‘r ' Diametrical Pitch - DP

No. of Pinion Teeth Outside Diameter OD

No. of Gear Teeth - ng Pitch Diameter - PD

‘ Angle of Helix a Centre Distance CIAddendum a

FOR SPUR GEARS

To Read English System D P Metric System Module

Circular Pitch 3.1416xPD cp _ 3.1416xPD

Centre Distance CD — tip x ng CD _ (np + ng) module

Diametrical Pitch DP = N _

Module PD Module=

Pitch Diameter PD = N PD = N x Module

Outside Diameter N + 9 -

•

[ FOR HELICAL GEARS

P i t c h D i a m e t e r__________________________ 1 ) —

Outside Diameter r OD = ______________ N

Centre Distance CD = PI) gear + PD pinion

L OD =

(Secent

a x N + 2) module

CDPD gear + PD pinion —

Specifications of Gear Robbing Machine, Capacity:

Smm Module - 500mm (Maximum)

SPECIFICATIONS

MAXIMUM MODULE/D.P. CUT

MAXIMUM VIA. OF GEARMAXIMUM WIDTH CUT OF SPUR GEARMAXIMUM WIDTH CUT OF HELICAL GEAR

HELIX ANGLE 15° HELIX ANGLE 300 HELIX ANGLE 45°DISTANCE BETWEEN HOB SPINDLE & SURFACE OF TABLE MIN. WITH BELLOWS

MAX. WITHOUT BELLOWSAXIAL DISTANCE BETWEEN TABLE & HOB SPINDLEHOB SPEED RANGE (RPM)RANGE AXIAL FEEDS OF HOB SLIDE MACHINE DIMENSION LXWXH WEIGHT OF MACHINEMAIN DRIVE MOTORRAPID MOTORCOOLANT PUMPSTANDARD EQUIPMENT: INDEXING GEAR SET

1 DIFFERENTIAL GEAR SETHOB ARBOR ONE

' WORK ARBOR ONE

PD = Secent a x N x module

2.5 MODULE350 MM250 MM

200 MM175 MM150 MM

327 MM 350 MM0 TO 175 MM35/50/60/90/115/14002 MM TO 4 MM1500 X 1000 X 1555 MM 1500 KGS.(APP-20X.)1.1 KW

0.36 KW0.11 KW

40 PCS. 40 PCS. 01 PCS. 01 PCS.



Expt. No: - Generating Helical gear on a Gear Blank Date: -

Aim: - To machine on given blank a helical gear profile using gemihobbing machine.

Tools required: - Verifier caliper, spanner, dot punch, hammer, centre bit, H.S.S cutting tool, dial gauge, etc..,

Materials required: - A cyl indr ica l work piece of d iameter s . . . inm, length mm of

cast iron rod.

Calculations: -

Number of Teeth Tooth Depth =

Module of Gear Circular Pitch =

Blank Diameter = Formula's: - Refer Page No

Procedure: -

I. The gear blank is fixed on mandrel and tightened by bolted.

2. The gear blank is checked for oval shape by dial gauge.

3. The hobbing cutter is made to just touch the gear blank.

4. The machine is started and cut is given by rotating tool on to the rotating blank.

5. The depth of cut is fed after I revolution and the operation is repeated until the finished gear shape is

achieved.

6. Apply coolant oil to carry away heat, and preventing wear on tool and rest on work.

7. Stop the machine and with draw the work and remove from mandrel. Now the machine is ready for next

machining.

8. Check the gear for pitch and gear teeth profile.

Result: - Thus the helical gear is generated on the gear blank using gear hobbing machine.

Shaper MachineShaping among the oldest techniques

D Shaping is where the work piece is fed at right angles to the cutting motion between successive strokes of

the tool.

These processes require skilled operators and for the most part have been replaced by

other processes.

Classification of Shapers Machine S>

Horizontal-push cut

Plain (Production work) Universal (Tool

room work)

Horizontal-draw cut St. Vertical S l o t t e r Key seater

S. Special purpose-as for gear cutting

Horizontal Push Cut Shaper

The shaper is a relatively simple machine. It is used fairly often in the tool room or for machining one or two pieces

for prototype work. Tooling is simple, and shapers do not always require operator attention while cutting. The

horizontal shaper is the most common type, and its principal components are shown below, and described as follows:

C. Ram: The ram slides back and forth in dovetail or square ways to transmit power to the cutter. The starting

point and the length of the stroke can be adjusted.

Tool head: The tool head is fastened to the ram on a circular plate so that it can be rotated for making

angular cuts. The tool bead can also be moved up or down by its hand crank for precise depth adjustments.

Clapper Box: The clapper box is needed because the cutter drags over the work on the

return stroke. The clapper box is hinged so that the cutting tool will not dig in. Often this clapper box is automatically

raised by mechanical, air, or hydraulic action.

C. Table: The table is moved left and right, usually by hand, to position the work under the curter wlig.n setting up.

Then, either by hand or more often automatically, the table moved sideways to feed the work under the cutter at

the end or beginning of each stroke.

Saddle: The saddle moves up and down (Y axis), usually manually, to set the rough

position of the depth of cut. Final depth can be set by the hand crank on the tool head.

Column: The column supports the ram and the rails for the saddle. The mechanism for moving the ram and table is

housed inside the column.

Tool holders: Tool holders are the same as the ones used on at engine lathe, though often larger in size. The cutter is

sharpened with rake and clearance angles similar to lathe tools though the angles are smaller because the work surface

is usually flat. These cutters are fastened into the tool holder. Just as in the lathe, but in a vertical plane.

4. Work holding...Work holding is frequently done in a vise. The vise is specially designed for use in. shapers and has

long ways which allow the jaws to open up to 14" or more, therefore quite large work pieces can be held. The vise

may also have a swivel base so that cuts may be made at an angle. Work that cannot be held in the vise (due to

size or shape) is clamped directly to the shaper table in much the same way as parts are secured on milling

machine tables.

Shaper Size: The size of a shaper is the maximum length of stroke which it can take. Horizontal shapers are most often

made with strokes from 16- to 24" long, though some smaller and larger sizes are available. These shapers use from 2- to

5-hp motors to drive the head and the automatic feed.

Shaper Width: The maximum width which can be cut depends on the available movement of the table. Most shapers

have a width capacity equal to or greater than the length of the stroke. The maximum vertical height available is about

12" to 15".

-

Types of Work: The tool post and the tool slide can be angled as seen below. This allows the shaper to be used for

different types of work.

(I)

(i) The tool post has been turned at an angle so that side of the material can be machined.

(ii) The tool post is not angled so that the tool can be used to level a surface.

(iii) The top slide is slowly feed into the material so that a 'rack' can be machined for a rack and pinion gear system.

Quick Return Mechanism

THE SHAPING MACHINE metal surfaces especially where a large

amount ot metal has to be removed. Other machines such as milling machines are much

ToolFeed

Cutting Tool

Stroke

StrokPave arc Aston*

Return Stroke

shaping machine is used to machine fit-

more expensive and are more suited to removing smaller amounts of metal, very accurately.

C.• The reciprocating motion of the mechanism inside the shaping machine can be seen in the diagram. As the disc

rotates the top of the machine moves forwards and backwards, pushing a cutting tool. The cutting tool

removes the metal from work which is carefully bolted down.

Ex. No:

Round to Square Using Shaper Machine

Aim: - To make the square shape from the cylindrical work piece on a shaper machine. Tools required: -

Single Point Tool (H.S.S), Vernier caliper, Adjustable spanner, key, hammer, etc... Materials required: A

cylindrical work piece of diameter ...mm and length of cast

iron rod.

Procedure:

1. The single point cutting tool is clamped in the tool post.

2. The surface of the material to be machined is marked.

3. The work piece is fixed in the machine vice, ensuring that it is parallel to the stroke of the ram. By elevating screw it is

brought to the required height.

4. The ram stroke is adjusted depending on the length of the work piece to account for speed variation.

5. Ram stroke = length of job + length of approach + length of over travel.

6. The table and the clapper box are moved so that the tip of the tool just touches the work piece.

7. Start the machine and the let the ram reciprocates, cutting during the forward stroke. During the return stroke

depth of cut is set by rotating the handle. Feed is also set simultaneously by cranking table feed screw. Feeding

can be automated if required.

8. After machining a groove on the work piece the "V" tool is removed and the parting tool is fixed. '

9. Finishing cut is given on the Square Shape and 4 sides.

10. Procedure is repeated for required size and shape.

Result: Thus a square shape from the cylindrical work piece on a shaper machine


- - i


PLANER MACHINE:

The planer like a shaper is a machine tool primarily intended to produce plane and fiat surfaces by a single point

cutting too).

A planer is very large and massive compared to a shaper and capable of machining heavy work pieces which

cannot be accommodated on a shaper table.

The fundamental difference between a shaper and a planer is that in a planer the work which is supported on the

table reciprocates past the stationary cutting tool and the feed is supplied by the lateral movement of the tool, whereas

in a shaper the tool which is mounted upon the ram reciprocates and the feed is given by the crosswise movement of the

table.

TYPES OF PLANING MACHINE

Different classes of work-necessitate designing of different types of planing machine to suit to various

requirements of our present day industry. The different types of planer which are most commonly used are:

I. Double housing planer. 4. Edge or plate planer.

2.Open side planer. 5. Divided table planer.

3.Pit planer

STANDARD OR DOUBLE HOUSING PLANER:

The standard or double housing planer is most widely used in workshops. A double housing planer has a long

heavy base on which a table reciprocates on accurate guide ways.

The length of the bed is little over twice the length of the table. Two massive vertical housings or uprights are

mounted near the middle of the base, one on each side of the bed. OPEN SIDE PLANER:

An open side planer has housing only on one side of the base and the cross rail is suspended from the

housing as a cantilever.

This feature of the machine allows large and wide jobs to be clamped on the table and reciprocated past the cutting

tool. One side of the planer being opened, large and wide out of the table and reciprocate without being interfered by the

housing.

In a double housing planer, the maximum width of the job which can be machined is limited by the distance

between the two housings

PIT PLANER:

A pit type planer is massive in construction. It differs from an ordinary planer in that the table is stationary

and the column carrying the cross rail reciprocates on massive horizontal rails mounted on both sides of the table.

This type of planner is suitable for machining a very large work which cannot be accommodated on a

standard planer and the design saves much of floor space.

The length of the bed required in a pit type planer is little over the length of the table, whereas in a standard

planer the length of the bed is nearly twice the length of the table.

The uprights and the cross rail are made sufficiently rigid to take up the forces while

cutting.

EDGE OR PLATE PLANER:

The design of a plate or edge planer is totally unlike that of an ordinary planer.

It is specially intended for squaring and beveling the edges of steel plates used for different pressore

vessels and ship-building works. One end of a long plate which remains stationary is clamped with the machine

frame by a large number of air operated clamps.

The cutting tool is attached to a carriage which is supported on two horizontal ways of the planer on its front

end. The operator can stand on a platform extending from the carriage.

The carriage holding the tool reciprocates past the edge of the plate. The feed and depth of cut is

adjusted by the tool holder which can be operated from the platform. DIVIDED TABLE PLANER:

This type of planner has two tables on the bed which may be reciprocated separately or together. This type of

design saves much of idle time while setting the work. The setting up of a large number of identical work pieces on

the planning machine table takes quite a long time. It may require as much time for setting up as may be necessary for

machining. To have a continuous production one of the tables is used for setting up the work, while the other

reciprocates past the cutting tool finishing the work. When the work on the second table is finished, it is stopped and

finished jobs are removed. Fresh jobs are now set up on this table while the first table holding the jobs now reciprocates

past the tool. When a heavy and large job has to be machined, both the tables are clamped together and are given

reciprocating movement under the tool.

PLANER MECHANISMS

The two important mechanisms of a planer are:

1. Table drives mechanism. 2. Feeding mechanism.

The different mechanisms used to drive the table are:

1. Open and cross belt drive. 2. Reversible motor drive. 3. Hydraulic drive.

OPEN AND CROSS BELT DRIVE: The open and cross belt drive of the table is used in a planer of smaller size where

the table width is less than 900 mm.


Ex. No: Round to Square Using PlannerAim: - To make the square shape from the cylindrical work piece on a planner machine. Tools required: -

Single Point Tool (H.S.S). Vernier caliper, Adjustable spanner, key, hammer, etc.. Materials required: - A

cylindrical work piece of diameter ...ram and length ...mm of cast iron rod.

Procedure:

1. The single point cutting tool is clamped in the tool holder.

2. The surface of the material to be machined is marked.

3. The work piece is fixed in the machine vice, ensuring that it is parallel to table travel.

4. Table travd1 is set by using trip dogs.

5. Distance = Approach + Key Length + Over Length.

6. Table and clapper box is moved such that tip of tool just touches maximum height of work.

7. Start the machine. As the table reciprocates, tool is fed, depth of cut set, machining operation starts during

rearward movement of table.

8. The over arm is used to set width of square shape and is achieved in proper gradual setup per stroke.

9. After machining with "V" tool. Parting off tool is set on tool holder after removing "V" tool.

10. With parting tool get required depth and width of square shape now enlarging cut made by "V" tool.

Check the dimension for accuracy.

Result:

Thus a quare shape from the cylindrical work piece on a planner machine

DRILLING MACHINE

INTRODUCTION

The drilling machine is one of the most important machines In workshop in a drilling machine holes may be

derived quickly and at a low cost.

The hole is generated by the rotating edge of a cutting tool known as the drill which exerts large force on the

work clamped on the table.

TYPES OF DRILLING MACHINE

Drilling machines are made in many different types and sizes, each designed to handle a 'class of work or

specific job to the best advantage. The different types of drilling machines are

1. Portable drilling machine.

2. Sensitive drilling machine. (a) Bench mounting,

3. Upright drilling machine. (a) Round column section,

4. Radial drilling machine. (a) Plain (c) Universal

5. Gang drilling machine.

6. Multiple spindle drilling machine.

7. Automatic drilling machine.

8. Deep hole drilling machine.

(a) Vertical, (b) Flour mounting

GANG DRILLING MACHINE

When a number of single spindle drilling machine columns are placed side by side on a common base and have

a common worktable, the machine is known as the gang drilling machine.

In a gang drilling machine four to six spindles may be mounted side by side. MULTIPLE SPINDLE

DRILLING MACHINE

The function of a multiple spindle drilling machine is to drill a number of holes in a piece of work

simultaneously and to reproduce the same pattern of holes in a number of identical pieces in a mass production work.

Once the work is loaded at the first machine, the work will move from one machine to the other where different

operations can be performed and the finished work comes out from the last unit without any manual handling.

This type of machine is intended purely for production purposes and may be used for milling, honing and similar

operations in addition to drilling and tapping.

DEEP HOLE DRILLING MACHINE

The machine is operated at high speed and low feed. Sufficient quantity of lubricant is pumped to the

cutting points for removal of chips and cooling the cutting edges of the drill.

A long job is usually supported at several points to prevent any deflection. The work is usually rotated while

the drill is fed into the work.

This helps in feeding the drill in a straight path. In some machines both4he work and the drill are rotated for

accurate location.

The machine may be horizontal or vertical type. In some machines step feed is applied. The drill is

withdrawn automatically each time when it penetrates into the work to a depth equal to its diameter. This process permits

the chip to Clear out from the work.

THE SIZE OF A DRILLING MACHINE

The size of a drilling machine varies with the type of machine being considered the sensitive and upright

drilling machines are specified by the diameter of the largest piece that can be centered under the spindle..

Thus in the case of a 600 nun size upright drilling machine, the spindle placed at a distance is slightly greater

than 300 mm from the front face of the column.

UPRIGHT DRILLING MACHINE PARTS

The different parts of an upright drilling machine are as follows:

Base • Table

Head s „ • Spindle drive and feed mechanism

C o l u m n

Spindle, quill and drill head assembly

Base: The base is that part of the machine on which vertical column is mounted.

Column: The column is the vertical member of the machine which supports the table and the head containing all the

driving mechanism.

Table: The table is mounted on the column and is provided with T-slots for clamping the work directly on its face

Spindle drive mechanism:

The spindle drive mechanism of a drilling machine incorporates an arrangement for obtaining multiple speed

of the spindle similar to lathe to suit to various machining conditions. Multiple speed of the spindle may be

obtained as follows:

4. By step cone pulley drive. 4 By gearing.

By step cone pulley drive with one or more back gears.

Step Cone Pulley Drive

Illustrates a spindle driving mechanism incorporating a step cone pulley. The motion is transmitted from an overhead line

shaft to the countershaft mounted on the base of the machine...

Step cone pulley drive with back gear In order to obtain larger number of spindle speeds back gears are incorporated in

the machine in addition to the step cone pulley.

With back gears "out" the speed of the spindle is increased and the machine is used for drilling smaller boles. For

drilling larger diameter holes or for tapping, the spindle speed is reduced by engaging the back gears.

Spindle drive by gearing:

Modem heavy duty drilling machines are driven by individual motor mounted on the frame of the machine. The

multiple speeds may be obtained by sliding gear or sliding clutch mechanism or by the combination of the above

two methods.

4. The sliding gear and sliding clutch mechanism in drilling is similar to that described in Art. 3/1.

Feed Mechanism:

In a drilling machine, the feed is affected by the vertical movement of the drill into the work. The feed movement of the

drill may be controlled by hand or power.

The hand feed may be applied by two methods:

Quick traverse hand feed Sensitive hand feed

Radial Drilling Machine Parts

1) The different parts of a radial drilling machine have been illustrated in Fig.5.3. They are as follows:

1. Base

2. Drill head

3. Column

4. speed and feed mechanism

5. Radial arm

Base:

The base of a radial drilling machine is a large rectangular casting that is finished on its top to

support a column on its one end and to hold the work table at the other end

Column:

The column is a cylindrical casting that is mounted vertically at one end of the base Radial arm:

The radial arm that is mounted on the column extends horizontally over the base. Drill head:

The drill head is mounted on the radial ann and drives the drill spindle. It encloses all the mechanism for

driving the drill at multiple speeds and at different feed.

Spindle drift 'and feed mechanism:

There are two common methods of driving the spindle. A constant speed motor is mounted at the

extreme end of the radial aim which balances partially the weight of the overhanging arm.

Work Holding Devices

Before performing any operation in a drilling machine it is absolutely necessary to secure the work firmly

on the

d

rilling machine table. The work should never be held by hand, because the drill while revolving exerts so much of

torque on the work piece that it starts revolving along with the tool and may cause injuries to the operator.

The devices commonly used for holding the work in a drilling machine are

I. T-bolt and clamps.

2. Dril l press vise .

3. S t e p b l o c k y

4. V - b l o c k .

5. A n g l e p l a t e .

6. D r i l l j i g s

Drilling Machine Operations

The different operations that can be performed in a drilling machine are:

1. Drill ing.

2. Reaming.

3. Boring.

4. Counter boring.

5. Counters inking.

6. Spot facing.

7. Tapping.

8. Lapping.

9. Grinding.

1. Trepanning.

Drilling:

Drilling is the operation of producing a cylindrical hole by removing metal by the rotating edge of a cutting

tool called the drill.

Reaming:

Reaming is an accurate way of sizing and finishing a hole which has previously drilled. In order to finish a hole and to

bring it to the accurate size, the hole is drilled slightly undersize. Boring:

HIA pressurecoolant

Boring is performed in a drilling machine for reasons stated below

1. To enlarge a hole by means of an adjustable cutting tool with only one cutting edge. This is necessary

where suitable sized drill is not available or where hole diameter is so large that it cannot be ordinarily

drilled.

2. Jo finish a hole accurately and to bring it to the required size.

3. To machine the internal surface of a hole already produced in casting.

4. To correct out of roundness of the hole.

5. To correct the location of the hole as the boring tool follows an independent path with respect to the

hole.

Lapping:

Lapping is the operation of sizing and finishing a small diameter hole already hardened by removing a

very small amount of material by using a lap. There are many kinds of lapping tools.

(ii) The copper head laps are commonly used. The lap fits in the hole and is moved down

while it revolves.

Grinding:

Grinding operation may be performed in a drilling machine to finish a hardened hole.

Preparing:

It is the operation of producing a hole by removing metal along the circumference of a hollow cutting

tool.

Nomenclature of Drill Tool

The following are the twist drill elements.

Axis: The longitudinal centre line of the drill. -

Body: That portion of the drill extending from its extreme point to the commencement of the neck, if present, otherwise

extending to the commencement of the shank.

Body clearance: That portico. Of the body surface which is reduced in diameter to provide diametric clearance.

Chisel edge:

S The edge formed by the intersection of the flanks. The chisel edge is also sometimes called- dead centre. The

dead centre or the chisel edge acts as a flat drill and cuts its own hole in the work piece.

Si A great amount of axial thrust is required to cut a hole by the chisel edge. In some drills

Chisel edge is made spiral instead of a straight one. This reduces the axial thrust and

Improves the hole location. Chances of production of oversize holes are also reduced. Chisel edge corner: The

'comer formed by the intersection of a lip and the chisel edge.

Face: The portion of the flute surface adjacent to the upon which the chip impinges as it is cut from the work.

Flank: That surface on a drill point which extends behind the lip to the following flute. Hates: The groove in the

body of the drill. Which provides lip

The functions of the flutes are:

I. To form the cutting edges on the point.

2.To allow the chips to escape.

3.To cause the chips to curl.

4.To permit the cutting fluid to reach the cutting edges.

Heel:

The edge formed by the intersection of the flute surface and the body clearance.

Lands:

The cylindrically ground surface on the leading edges of the drill flutes. The width of the land is measured at

right angles to the flute helix. The drill is MI size only across the lands at the point end. Land keeps the drill aligned.

Lip (cutting edge):

The edge formed by i he intersections of the flank and face. The requirements of the drill lips are:

1. Both lips should be at the same angle of inclinatory with the drill axis,

2. Both lips should be of equal length.

3. Both lips should be provided with the correct clearance.

Neck: The diametrically undercut portion between the body and the shank of the drill. Diameter and other

particulars of the drill are engraved at the neck.

DRILL MATERIAL

The materials for the manufacture of twist drills are as follows

I. One piece construction : High speed steel or carbon steel.

2. Two piece construction

Cutting portion — High speed steel

Shank portion — Carbon steel with a minimum tensile strength of 70 kg per sq mm

High speed drills are more widely used due to its greater cutting efficiency. Cemented carbide tipped drills is also

used in mass production work.

Ex. No: Dril l ing, Reaming and Tapping

- To perform drilling, reaming and tapping operation on the given work piece. Tools required: -

Drill Bit (required sizes), Drill chuck, Chuck key, Table key, Drill sleeve, Vernier caliper, Adjustable

spanner, Hammer, Center drill bit, reaming tool, tapping set, steel rule, Oil can, etc...

Materials required: - A rectangular plate work piece of length mm, width . . .mm,

thickness ....mm, of Mild steel (MS) Plate.

Procedure:

Drilling:

L. The layout of the holes to be drilled is done from a sketch.

2. The surface of the material to be drilled is first coated layout die.

3. The center lines of the holes are then scribed on the surface according to dimensions.

4. The intersection of the lines is then marked with a center punch.

5. A combined drill and a counter sink is used to center drill the holes.

6. Fix the required size of drill bit in the drill chuck and drill the component.

7. Coolant oil is applied a drill point. Coolant oils are used to carry heat away from the drill point.

Drilling:

Reaming is the operation of finishing the drilled hole. A finished hole has the specific diameter size, is perfectly

round. The diameter is the same size from end to end and it has a smooth "finished surface. A drilled hole is seldcim

accurate enough in size or sufficiently smooth to be called a precision hole. When greater accuracy is required the

hole must be drilled under size by certain amount and finished in the drill chuck.

I. The reamer tool is fixed in the drill chuck.

2. The drilled hole is reamed by giving feed.

3. Reamer tool removes very small amount of material and machine the whole precision. Tapping:

A tap is a cylindrical bar of steel with threads formed around it and grooves or flutes running length wise in it,

intersecting with the threads to form cutting edges. It is used to cut internal threads.

A set of tap consists of three taps known as taper, plug and bottoming taps. The taper tap is used to start the

cutting of the threads and of the hole is blind than a plug tap is used to

Complete the cutting of the threads near the bottom of the hole. When it is necessary for the threads at the bottom of

a hole to be fully cut then a bottoming tap is used.

1. The taper tap is hold in the tap wrench. (A tap wrench is a hand tool for gripping and holding the tap securely

size of taps a "T" handle type is used.)

2. The location of the hole is properly laid out and a hole is drilled.

3. The taper tap is inserted in to the drilled hole. When starting the tap in to the whole care must be taken to keep the

tap perpendicular to the work.

4. The tap should be revolved only one half a rotation at a time after which it should be reversed in order to break the

chips of metal before revolving forward again. Coolant is applied at the hole during operation.

5. The above procedure is repeated until the .full length of the hole is tapered.

Result:

Thus the drilling, reaming and tapping operation are performed on the given

workpiece.



SLOTTER MACHINE -

Slotting machines can simply be considered as vertical' shaping machine where the single point

(straight or formed) reciprocates vertically (but without quick return effect) and the workpiece, being mounted

on the table, is given slow longitudinal and / or rotary feed as can be seen in Fig. 4.4.4. In this machine also

the length and position of stroke can be adjusted. Only light cuts are taken due to lack of rigidity of the

tool holding ram for cantilever mode of action. Unlike shaping and planing machines, slotting machines

are generally used to machine internal surfaces '(flm, formed grooves and cylindrical).

Shaping machines and slotting machines, for their low productivity, are generally used, instead of

;general production, for piece production required for repair and maintenance,' Like shaping kslotting machines,

planing machines, as such are also becoming obsolete t, and •getting replaced by piano-millers where instead of

single point tools a large number of large size and high speed milling cutters are used.

ROTATING TABLE

Ex. No: Make internal Key way by using slotter

Aim: - To perform an internal keyway operation on the given work piece by using slotter machine.

Tools required: - Cutting tool, steel rule, vernier caliper, spanners, center punch, hammer etc...

Materials required: - A cylindrical work piece of diameter ....................................mm and length .mm of

cast iron rod.

• Procedure:

1. The given job dimensions are checked.

2. Marking produced on the work piece as per required dimensions using centre punch. t,

3. Fix the work piece on the slotter machine table.

4. Fix the tool on the vertical tool head of the slotter machine.

5. The tool is fed against the work piece to produce keyway on the work piece.

6. The' finished work piece is taken out from the machine and again checked for its dimensions.

Result:

Thus the required size and shape of the work piece obtained using stutter machine.

IN JOB

4._ I 4 I 25

_______________50

GIVEN JOB


i


Documents

IV Sem Mech_mt -II Lab Manual