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Machines arrangement according to

layout:1: Power Hacksaw

2: Universal Shearing

3: Tool and Cutter Grinding

4: Lathe Machine

5: Lathe Machine

6: Tool and Cutter Grinding Machine

7: Tool and Cutter Grinding Machine

8: Surface Grinding Machine

9: Plain knee and Milling Machine

10: Shaping Machine

11-15: Lathe Machine

16-20: Lathe Machine

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INTRODUCTION TO MACHINE SHOP

MACHINE SHOP:A machine shop is a room, building, or company where machining is done. In amachine shop , machinists use machine tools and cutting tools to make parts,usually of metal or plastic (but sometimes of other materials such as glass orwood).

MACHINE TOOLS:

A machine tool is a machine for shaping or machining metal or other rigidmaterials, usually by cutting, boring, grinding , shearing, or other forms ofdeformation. Machine tools employ some sort of tool that does the cutting orshaping. All machine tools have some means of constraining the workpieceand provide a guided movement of the parts of the machine.

Introduction to Machines

LATHE MACHINE:Lathe was actually the first machine tool which came into being as auseful machine for metal cutting. Lathe can be defined as a machine toolwhich holds the work between two rigid and strong supports, calledcentres, or in a chuck or Face plate while the lathe revolves. Thefollowing are some of the important Parts of lathe machine

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Parts of lathe machine

BED:

The bed of Lathe acts as the base on which the different fixed and operationsparts of the Lathe are mounted. Lathe beds are usually made as single piececasting of semi-steel (i.e., toughened cast iron),with the addition of small quantity of steel scrap to the cast iron duringmelting; the material ‘cast iron’ facilitating an easy sliding action. In case of

extremely large machines, the bed may be in two or more pieces, boltedtogether to from the desired length. Lathe Bed are heavy rigid structure whichis having high damping capacity for the vibrations generated by machinesduring machining. The rigid structure will helps to avoid deflections. The guidesand ways which are present on the top of the bed will act as rails and supportsother parts like tail stock. The bed will be designed in such a way that easilybolted to the floor of the machine shop.

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Head stock

The head stock is the part of the lathe which serves as a housing for the drivingpulleys and back gears, provides bearing for the machine spindle and keeps thelatter in alignment with the bed. It is a fixed part which will present on the leftside of the lathe bed. Head stock will consists of a hollow spindle and drives unitlike main spindle, feed reverse lever, live center cone pulley etc., The taperedbar with pointed or projected end is going to grip the work piece between twocenters of lathe bed .

Tail stockIt is also sometimes called the LOOSE HEAD- STOCK or PUPPET HEAD. It ismounted on the bed of the lathe such that it is capable of sliding along thelatter maintaining its alignment with the head stock. On common types ofmedium size or small size lathes it is moved along the bed by hand, whereas inheavier types of lathes it is moved by means of a hand wheel through a pinionwhich meshes with the rack provided on the front of the lathe bed. The main

function of the Tail stock is to provide bearing and support to the job which isbeing worked between centers.To enable this, the tail stock is made to possessa number of parts which collectively help in its successful function.

Tail stock

It is also sometimes called the LOOSE HEAD- STOCK or PUPPET HEAD. It ismounted on the bed of the lathe such that it is capable of sliding along the

latter maintaining its alignment with the head stock. On common types ofmedium size or small size lathes it is moved along the bed by hand, whereas inheavier types of lathes it is moved by means of a hand wheel through a pinionwhich meshes with the rack provided on the front of the lathe bed. The mainfunction of the Tail stock is to provide bearing and support to the job which isbeing worked between centers.To enable this, the tail stock is made to possessa number of parts which collectively help in its successful function .

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Carriage

The lathe carriage serves the purpose of supporting, guiding and feeding thetool against the job during the operation of the lathe. The carriage willpresent between head stock and tail stock which will slides on the bed waysof the lathe bed. The carriage will give feed to the tool and it holds the tool,for taper turning the feed is cross feed, for turning it is longitudinal feed. Thecarriage consists of the following parts.1. saddle2. cross-slide

3. compound Rest4. Tool post5. Aprone

Saddle

It is the part of the carriage which slides along the bed way and support theCross-slide,compound rest and Tool post.

Cross-slide

The cross-slide function is to provide cutting action to the tool and the actionof cutting tool will be perpendicular to center line of lathe.It can either beoperated by hand, by means of the cross-feed screw, or may be given powerfeed through the Apron Mechanism.

Compound Rest

The compound Rest will be placed over the cross slide and it consists of agraduated circular base which is having swiveling nature.

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Tool post

It is the top most part of the carriage and is used for holding the tool or toolholder in position.

Aprone

Aprone houses the feed mechanism, clutch mechanism split half nut, gears,leavers, The apron wheel can be rotated by hand for longitudinal motion ofthe carriage.

Legs

They are the supports which carry the entire load of the machine overthem.The prevailing practice is to use cast legs. Both the legs are firmlysecured to the floor by means of foundation blots in order to preventvibrations in the machine. One of these legs, usually the one on the left handside of the operator, serves as a housing for the electric motor andcountershaft etc., Both these legs should be of robust construction.

Operations on lathe machine

1. Plain Turning and Step Turning

2. Facing

3. Parting

4. Drilling

5. Reaming

6. Boring

7. Knurling

8. Grooving

9. Threading

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L th ’s Operations

The general operations done with the lathe are grooving, turning, cutting,

sanding and etc. if anyone wants to operate the lathe machine then he mustfirst know about the feeds, cutting speed, depth of the cut and usage of toolshould be considered. Each lathe operation has got its own factors that needto be considered before doing the work. The factors should be used properlyso that one can avoid from mishandling and mishaps while performing anykind of lathe operation. With every cut desired the speed, depth and feed ofthe lathe machine is changed for precision.

Types of Lathe OperationThe working of the lathe machine changes with every operation and cutdesired. There are a lot of operations used for using the lathe machine. Someof the common lathe operations are:

Facing

This is usually the first step of any lathe operation on the lathe machine. Themetal is cut from the end to make it fit in the right angle of the axis andremove the marks .

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Facing :

Facing is the operation of machining the ends of a piece of work to produce aflat surface square with the axis. This is also used to cut the work to therequired length. The operation involves feeding the tool perpendicular to theaxis of rotation of the work piece. A properly ground facing tool is mountedin a tool holder in the tool post. A regular turning tool may also be used forfacing a large work piece. The cutting edge should be set at the same heightas the centre of the work piece. The selection of hand-feed or power feeddepends upon the length of the cut. The surface is finished to the size bygiving usual roughing and finishing cuts. For roughing, the average value of

the cross feed is from 0.3 to 0.7 mm per revolution and the depth of cut isfrom 2 to 5 mm. For finishing, the feed ranges from 0.1 to 0.3 mm per rev.and the depth of cut is from 0.7 to 1 mm.

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Knurling :Knurling is the process of embossing a diamond shape pattern on the surface

of a work piece. The purpose of knurling is to provide an effective grippingsurface on a work piece, to prevent it from slipping when operated by hand.In some press fit work knurling is done to increase the diameter of a shaft.The operation is performed by a special knurling tool which consists of a setof hardened steel rollers in a holder with the teeth cut on their surface in adefinite pattern. Knurls are available in coarse, medium and fine pitches.

Recessing : Recessing can also be called as grooving or necking. So the recessing toolsare sometimes called necking tools. Recessing tools may be either straight orbent shank types. As the recess is usually narrow, the cutting edge is keptnarrow. It is relieved by 1 o to 2 oon each side towards the shank. The sides arerelieved to make the tool free cutting. The rake angle should be decreased or

the face should be made hollow to the radius. The tool should be set exactlyin centre. If tool is set below or above the centre, it will break.

Shoulder Turning :When a workpiece having different diameters is turned, the surface formingthe step from one diameter to the other is called the shoulder, andmachining this part of the workpiece is called shoulder turning.

Thread Cutting :Thread cutting is one of the most important operations performed in a lathe.The principle of thread cutting is to produce a helical groove on a cylindricalor conical surface by feeding the tool longitudinally when the job is revolvedbetween centres or by a chuck. The longitudinal feed should be equal to thepitch of the thread to be cut per revolution of the workpiece.

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The depth of cut, which usually varies from 0.05 to 0.2 mm, is applied byadvancing the tool perpendicular to the axis of the work. After the tool hasproduced a helical groove upto the end of the work, it is quickly withdrawnby the use of the cross slide, the half nut disengaged, and the tool is broughtback to the starting position to give a fresh cut. Before re-engaging the halfnut, it is necessary to ensure that the tool will follow the same path it hastraversed in the previous cut, otherwise the job will be spoiled. Several cutsare necessary before the full depth of thread is reached.

Internal Threadcutting:

The principle of cutting internal threads is similar to that of an

external thread, the only difference being in the tool used. The toolis similar to a boring tool with cutting edges ground to the shapeconforming to the type of thread to be cut. The hole is first boredto the root diameter of the thread. The tool is fixed on the tool postor on the boring bar after setting it at right angles to the lathe axis,using a thread gauge/angle gauge.

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The depth of cut is given by the compound slide and the thread isfinished in the usual manner.

Boring : Boring is the operation of enlarging and truing a hole produced by drilling,

punching, casting or forging. Boring cannot originate a hole. Boring is similarto the external turning operation and can be performed in a lathe.

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Counter Boring:

Counter Boring is the operation of enlarging a hole through a certaindistance from one end instead of enlarging the whole drilled surface. Itis similar to a shoulder turning operation in external turning.

Taper Boring:

The principle of turning a taper hole is similar to the external taperturning operation and is accomplished by rotating the work on a chuckand feeding the tool at an angle to the axis of rotation of the work piece.

Plain or Straight Turning:

Plain Turning or Straight Turning. The work is turned straight when it is madeto rotate about the lathe axis, and the tool is fed parallel to the lathe axis. Thestraight turning produces a cylindrical surface by removing excess metal fromthe work piece. After facing the ends and drilling the centre, the job is carefullymounted between the centres using a lathe dog attached to the work piece. A

properly ground right hand turning tool is used for this purpose. Tool isclamped on the tool post with the minimum overhang and is set with itscutting edge approximately at the lathe axis or slightly above it. For light cutsthe tool may be inclined towards the headstock, but for heavy cuts the toolmust be inclined towards the tailstock. The automatic feed is engaged to movethe carriage to the desired length, then the feed is disengaged and the carriageis brought back to the starting position. The process is repeated until the jobis finally finished.

There are two kinds of cuts that can be given onto a work piece: Rough Turning& Finish Turning

Rough Turning: The rough turning is the process of removal of excessmaterial from the work piece in a minimum time by applying high rate of feedand heavy depth

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of cut. The roughing cut should be so made that the machine, the tool, andthe work piece can bear the load. The depth of cut for roughing operations inaverage machine shop work is from 2 to 5mm and the rate of feed is from 0.3to 1.5 mm per revolution of the work. Rough turning operations are carriedout by rough turning tool.

Finish Turning:

The finish turning operation requires high cutting speed, small feed, and avery small depth of cut to generate a smooth surface. A finish turning toolhaving sharp cutting edge is held securely on the tool post for this purpose. Infinish turning operation, the depth of cut ranges from 0.5 to 1 mm and feedfrom 0.1 to 0.3 mm per revolution of the work piece. The cross feed dial isused to set an accurate depth of cut. After measuring the diameter of roughturned surface, the depth of cut to be given is determined by subtracting thefinished diameter from the measured value. The tool is then made to advanceby half of the above value by rotating the cross slide hand-wheel throughrequired number of divisions on the dial. The machine is started and a trial cutis made from the end of the work to 5 or 6 mm by applying hand feed and the

finished diameter is checked by a micrometer. Once the correct diameter ismade, the rest is finished by the automatic feed.

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Chamfering:

Chamfering is the operation of beveling the extreme end of a workpiece. This

is done to remove the burrs, to protect the end of the workpiece from beingdamaged and to have a better look. The operation may be performed afterknurling, rough turning, boring, drilling. Chamfering is an essential operationbefore thread cutting so that the nut may pass freely on the threadedworkpiece.

Parting Off : Parting-off is the operation of cutting a workpiece after it has been machined

to the desired size and shape. The process involves rotating the workpiece ona chuck or faceplate at half the speed to that of turning and feeding by anarrow parting off tool perpendicular to the lathe axis by rotating the crossslide screw by hand. Before the operation starts, the carriage is locked inposition on the lathe bed and the cutting tool is held rigidly on the tool post

with the compound slide set parallel to the lathe axis. The tool should be fedvery slowly to prevent chatter. The feed varies from 0.07 to 0.15 mm perrevolution and the depth of cut is equal to the width of the tool. In parting off,a work of very large diameter, cuts are made in stages. The parting off tool isfirst fed through a certain depth, then withdrawn and two more cuts are madeat the two sides of the central groove. The tool is next fed into the centralgroove until the work is cut off in two parts.

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General Lathe OperationsLATHE SPEEDS, FEEDS, AND DEPTH OF CUTS

General operations on the lathe include straight and shoulder turning, facing,grooving, parting, turning tapers, and cutting various screw threads. Before theseoperations can be done, a thorough knowledge of the variable factors of lathespeeds, feeds, and depth of cut must be understood. These factors differ for eachlathe operation, and failure to use these factors properly will result in machine failure

or work damage. The kind of material being worked, the type of tool bit, the diameterand length of the workpiece, the type of cut desired (roughing or finishing), and theworking condition of the lathe will determine which speed, feed, or depth of cut isbest for any particular operation. The guidelines which follow for selecting speed,feed, and depth of cut are general in nature and may need to be changed asconditions dictate.

Cutting Speeds.

The cutting speed of a tool bit is defined as the number of feet of workpiece surface,measured at the circumference, that passes the tool bit in one minute. The cuttingspeed, expressed in FPM, must not be confused with the spindle speed of the lathewhich is expressed in RPM. To obtain uniform cutting speed, the lathe spindle must berevolved faster for workplaces of small diameter and slower for workplaces of largediameter. The proper cutting speed for a given job depends upon the hardness of thematerial being machined, the material of the tool bit, and how much feed and depth ofcut is required . Cutting speeds for metal are usually expressed in surface feet perminute measured on the circumference of the work. S indle revolutions er minute

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are determined by using the formula:

12 X SFM = RPM

3.1416 X D

Which is simplified to:

4 X SFM = RPM

D

Where SFM is the rated surface feet per minute, also expressed as cutting speed.

RPM is the spindle speed in revolutions per minute

D is the diameter of the work in inches.

In order to use the formula simply insert the cutting speed of the metal andthe diameter of the workpiece into the formula and you will have the RPM.

Feed

Feed is the term applied to the distance the tool bit advances along the

work for each revolution of the lathe spindle. Feed is measured in inches ormillimeters per revolution, depending on the lathe used and the operator'ssystem of measurement. Table 3-3 in Appendix A is a guide that can be usedto select feed for general roughing and finishing operations. A light feed mustbe used on slender and small workplaces to avoid damage. If an irregularfinish or chatter marks develop while turning. reduce the feed and check thetool bit for alignment and sharpness. Regardless of how the work is held inthe lathe, the tool should feed toward the headstock. This results in most of

the pressure of the cut being put on the work holding device. If the cut mustbe fed toward the tailstock. use light feeds and light cuts to avoid pulling theworkpiece loose.

Depth of Cut

Depth of cut is the distance that the tool bit moves into the work. usually

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measured in thousandths of an inch or in millimeters. General machine practiceis to use a depth of cut up to five times the rate of feed, such as rough cuttingstainless steel using a feed of 0.020 inch per revolution and a depth of cut of

0.100 inch. which would reduce the diameter by 0.200 inch. If chatter marks ormachine noise develops. reduce the depth of cut. T urning a one-half inch pieceof aluminum. cutting speed of 200 SFM. would result in the following:

4 x 200 = 1600 RPM

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Things To Remember:

Materials that are machined dry without coolant. require a slower cuttingspeed than operations using coolant. Lathes that are worn and in poorcondition will require slower speeds than machines that are in good shape. Ifcarbide-tipped tool bits are being used, speeds can be increased two to threetimes the speed used for high speed tool bits.

References

http://www.smithy.com/machining-handbook/chapter-3/page/21 , retrieved 21 st January,2016.

http://www.engineeringarticles.org/lathe-lathe-operations-types-and-cutting-tools/ , reterived 21 st January, 2016.

http://www.educationportals.net/lathe-machine-operations-chamfering-parting-off/ , retrieved 21 st Janauary, 2016