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Study of LATHE machine The lathe is one of the oldest machine tools and came into existence from the early tree lathe which was then a novel device for rotating and machining a piece of work held between two adjacent trees. A rope wound round the work with its one end attached to a flexible branch of a tree and the other end being pulled by a man caused the job to rotate intermittently. Hand tools were then used. With its further development a strip of wood called “lath” was used to support the rope and that is how the machine came to be known as “lathe”. This device continued to develop through centuries and in the year 1797 Henry Maudslay, an Englishman, designed the first screw cutting lathe which is the forerunner of the present day high speed, heavy duty production lathe a machine tool which has practically given shape to our present day civilization by building machines and industries.

TYPES OF LATHE The types generally used are : 1. Speed lathe. (a) Wood working. (b) Centering. (c) Polishing. (d) Spinning. 2. Engine lathe (a) Belt drive. (b) Individual motor drive. (c) Gear head lathe. 3. Bench lathe. 4. Tool room lathe. 5. Capstan and Turret lathe. 6. Special purpose. (a) Wheel lathe. (b) Gap bed lathe. C.O.E.& T.Akola.

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(c) T-lathe. (d) Duplicating lathe. 7. Automatic lathe. DESCRIPTION AND FUNCTION OF LATHE PARTS Fig. illustrates the basic parts of a geared head lathe. Following are the principal parts: 1. Bed.

4. Carriage

2. Headstock.

5. Feed mechanism.

3. Tailstock.

6. Screw cutting mechanism.

THE BED The lathe bed forms the base of the machine. The headstock and the tailstock are located at either end of the bed and the carriage rests over the lathe bed and slides on it. The lathe bed being the main guiding member of the tool, for accurate machining work, must satisfy the following conditions : 1. It should be sufficiently rigid to prevent deflection under tremendous cutting pressure transmitted through the tool-post and carriage to the lathe bed. 2. It must be massive with sufficient depth and width to absorb vibration. 3. It must the twisting stress set up due to the resultant of two forces- the downward cutting force on the tool and the force tending to move the tool away from the 2003-04

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work in a horizontal direction. This is best done by diagonal ribbing or making box section casting shown in Fig.

Box Section Lathe Bed 4. The bed should be seasoned naturally to avoid distortion or warp that may develop when it is cooled after the bed is cast. On the top of the bed there are two sets of slides or guideways- outerways and innerways. The outer guideways provide bearing and sliding surfaces for the carriage, and the innerways for the tailstock. The guiding surfaces are accurately machined to make them parallel to the lathe axis, absolutely horizontal, and sufficiently plain. The guiding surface should also be resistant to wear.

Chilled castings are sometimes used to improve wear

resisting qualities.

Lathe Bed Diagonal Ribs 1. Diagonal rib, 2. Bedways. The guideways of the lathe bed may be flat and inverted – V having an included angle of 900. The wide flat guideways provide a large bearing surface with C.O.E.& T.Akola.

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corresponding reduction in wear. Obviously the bearing surface requires particular care and attention to keep it always clean and perfectly smooth. In this type of guideways some adjustment of saddle keep-plates is necessary after wear.

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inverted V type guideways, although expensive to machine, provide better guide for carriage and tailstock, ensure accurate alignment, and are unaffected by any wear. The shape of the V is such that the chips automatically fall through. But it has a small bearing surface which results increase in wear. This also weakens the saddle. Both V and flatways for each set of guideways are more commonly used to combine the advantages of both the types. Fig. illustrates different types of lathe bedways. Many lathes are made with a gap in the bed. This gap is used to swing extra large diameter pieces.

The bed material should have high compressive strength, should be wear resistant and absorb vibration. Cast iron alloyed with nickel and chromium forms a good material suitable for lathe bed.

THE HEADSTOCK The headstock is secured permanently on the innerways at the left hand end of the lathe bed, and if provides mechanical means of rotating the work at multiple speeds. It comprises essentially a hollow spindle and mechanism for driving and altering the spindle speed. All the parts are housed within the headstock casting.

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The spindle of the headstock, illustrated in Fig. is made of carbon or nickel chrome steel. This is usually of a large diameter to resist bending and it should be perfectly aligned with the lathe axis and accurately machined for producing true work surface. A hole extends through the spindle so that a long bar may be passed through the bore. The front end of the hole is appeared for holding centers and other tools having a standard Morse tape shank. A taper sleve fits into the taper hole, and a live center which supports the work and revolves with the work fits into the sleeve that acts as a bush. There are two common types of spindle

noses: the threaded design

which carries the chuck, driving plate and face plate, and the flanged nose which enable them to be directly attached. The lathe most commonly used has a threaded spindle nose.

TAIL STOCK OR LOOSE HEADSTOCK The tailstock is located on the innerways at the right hand end of the bed. This has two main uses : (1) it supports the other end of the work when it is being machined between centers, and (2) it holds a tool for performing operations such as drilling, rearing, tapping, etc. A tailstock is illustrated in Fig. To accommodate different lengths of work, the body of the tailstock can be adjusted along the ways chiefly by sliding it to the desired position where it can be clamped by bolts and plates. The upper casting of the body can be moved toward or away from the operator by means of the adjusting screws to offset the tailstock for taper turning and to realign the tailstock center for straight turning. The body is bored to act as the barrel, which carries the tailstock spindle that moves in and out of the barrel by means of a screw when the tailstock handwheel is turned. The front of the C.O.E.& T.Akola.

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spindle has a taper hole into which the dead center or other tools fit. The screw thread is left handed, so that clockwise rotation of the handwheel causes the spindle to advance, while as clockwise rotation causes the spindle to be drawn inward and ultimately the end of the screw strikes the back of the dead center or any tool that is fitted into the hole. To remove tools from the spindle, it is therefore, only necessary to back up on the handwheel until the spindle end is nearly inside the casting. The spindle has a key way in the underside which mates with a small key fitted on the barrel to prevent rotation. After the adjustment is made, the spindle is clamped in position by tightening the locking bolt on split lug.

CARRIAGE The carriage of a lathe has several parts that serve to support, move and control the cutting tool. It consists of the following parts : (1) saddle, (2) cross-slide, (3) compound slide or compound rest, (4) tool post, and (5) apron. A sectional view of the carriage is shown in Fig. Saddle : The saddle is an H-shaped casting that fits over the bed and slides along the ways. It carries the cross slide and tool post. Some means are generally provided for locking the saddle to prevent any movement when surfacing operations are carried out. The cross-slide : The cross-slide comprises a casting, machined on the underside for attachment to the saddle and carries locations on the upper face for the tool post or

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compound rest. The cross-piece of the saddle is mechanized with a dovetail way, at right angles to the center axis of the lathe, which serves to guide the cross-slide itself. In order to move the cross-slide, the feed screw is turned by rotating the handwheel. Transverse movement is obtained when the nut mounted on the feed screw is engaged with the binder screw of the cross-slide. When a taper turning attachment is used the binder screw of the cross-slide.

When a taper turning

attachment is used the binder screw is opened to disconnect the cross-slide from the cross-feed screw, and the extension of the slide is attached with the guide block shown in Fig. Automatic movement of the cross-slide is obtained when the pinion keyed to the cross-feed screw is in mesh with the apron gearing.

1. Tool post screw, 2. Tool post, 3, Rocker, 4. Tool 5. Concave ring. 6. Compound rest swivel base. 7. Crossfeed screw, 8. Binder screw, 9. Cross slide, 10. Cross-slide nut, 11. saddle, 12. Pinion on Crossfeed screw for automatic feed, 13. Cross slide hand wheel, 14. Compound slide hand wheel, Compound slide feed screw, 16. Compound rest, 17. Compound slide nut.

Usually cross-slide hand wheels are graduated on their rims, or a separate micrometer dial may be fitted on them so that a known amount of feed can be applied. One small division of the dial is equal to 0.05 mm. The compound rest : The compound rest or compound slide is mounted on the top of the cross-slide and has a circular base graduated in degrees. It is used for obtaining angular cuts and short tapers as well as convenient positioning of the tool to the work. By loosening two set-screws which fit in a V-groove around the compound-test base, C.O.E.& T.Akola.

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the rest or the slide may be swiveled to any angle within a circle. There is no power feed to the compound rest and it is hand operated. The compound-rest handle is also equipped with a micrometer dial to assist in determining the depth of the cut. After necessary setting the compound slide is locked solid with its base. The tool post : This is located on the top of the compound rest to hold the tool and to enable it to be adjusted to a convenient working position. The type and mounting of the tool post depends upon the class of work for which it is to be used. The rigidity of the tool holder and effective method of securing are the essential factors in designing a tool post. Following are the common types of tool post : 1. Single screw tool post

3. Open side tool post.

2. Four bolt tool post

4. Four way tool post.

1. Toolpost screw, 2. Toolpost body, 3. Tool, 4. Convex rocker, 5. Concave ring.

FEED MECHANISM The moment of the tool relative to the work is termed as “feed”. A lathe tool may have three types of feed-longitudinal, cross, and angular. When the tool moves parallel to the lathe axis, the movement is termed as longitudinal feed and is effected by the movement of the carriage. When the tool moves at right angle to the lathe axis with the help of the cross slide the movement is termed as cross feed, while the movement of the tool by compound slide when it is swivelled at an angle to the lathe axis is termed as angular feed. Cross and longitudinal feed are both hand and power operated, but angular feed is only hand operated.

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The feed mechanism has different units through which motion is transmitted from the headstock spindle to the carriage. Following are the units : 1. End of bed gearing. 2. Feed gear box. 3. Feed rod and lead screw. 4. Apron mechanism. THREAD CUTTING MECHANISM The rotation of the lead screw is used to transverse the tool along the work to produce screw thread. The half-nut mechanism illustrated in Fig. makes the carriage to engage or disengage with the lead screw. It comprises a pair of half nuts 7 capable of moving in or out of mesh with the lead screw. The two halves of the nut are connected in the cam slots 1 in a circular disc 6 by two pins 5. When the disc is rotated by a hand lever 4 attached to it, the pins being guided in the cam slots serve to open or close the split nuts and thus engages or disengages with the lead screw. The half nuts slide within the guide or frame 2. Closing the half nuts causes the carriage to move a fixed distance for each revolution of the spindle. The direction in which it moves depends upon the position of the feed reverse level on the headstock. The split nut is used only for thread cutting and never for any other operation.

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THE BACK GEAR The back gear is an additional feature of a belt driven lathe and this is used to obtain wider range of spindle speeds, for the number of speeds obtained from “direct speeds” is limited to the number of steps only. When the back gear is engaged, the spindle speed reduces considerably. So it is also used when it is necessary to have a slow speed of the spindle that cannot otherwise be obtained by direct speed. A slow speed is necessary in the following cases : 1. In turning jobs of large diameter within the available cutting speed of the material. 2. In turning jobs of tough or hard material. When the material is hard it becomes necessary to apply greater cutting force by the tool to shear out the metal. This increase in cutting force will require greater turning torque necessitating slower spindle speed. 3. In operations like thread cutting, reaming, etc. 4. In taking deep cut as in rough turning.

LATHE OPERATIONS Operations which are performed in a lathe either by holding the workpiece between centres or by a chuck are : 1. Straight turning.

8. Taper turning.

2. Shoulder turning.

9. Eccentric turning.

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4. Thread cutting.

11. Grooving.

5. Facing.

12. Spinning.

6. Knurling.

13. Spring winding.

7. Filing.

14. Forming.

Operation which are performed by holding the work by a chuck or a faceplate or an angle plate are : 1. Drilling

6. Internal thread cutting

2. Reaming

7. Tapping

3. Boring

8. Undercutting

4. Counterboring

9. Parting-off

5. Taperboring Operations which are performed by using special attachments are: 1. Grinding

2. Milling

CENTERING Where the work is required to be turned between centres or between a chuck and a centre, conical shaped holes must be provided at the ends of the work piece to provide bearing surface for lathe centres. Centering is the operation of producing conical holes in work pieces. To prepare a cylindrical work piece for centering, it is first necessary to locate the centre hole by marking off. This is done by rubbing the end with a chalk and the centre may be located by any one of the following instruments : (1) using a centre head and steel rule of a combination set, (2) using a hermaphrodite caliper, (3) using a divider and surface plate, (4) using a surface gauge, and (5) using a bell centre punch. After the centre has been located, a centre punch and a hammer are used to make a deep indentation to produce the hole to hold and to revolve the work on lathe centres. Centre holes are produced by using a combined drill and countersink tool. This is held on a drill chuck and may be mounted on the headstock or on the tailstock spindle to produce a conical hole on the ends of the work piece. The included angle of the hole should be exactly 600 to fit with the 600 point angle of the lathe centres. The straight hole projected beyond the conical

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hole serves as a small reservoir for lubricating oil and relieves the tip of the dead centre from rubbing with the work piece. TURNING 1) Straight turning : The work is turned straight when it is made to rotate about the lathe axis, and the tool is fed parallel to the lathe axis. The straight turning produces a cylindrical surface by removing excess metal from the work piece. After facing the ends and drilling the centre, the job is carefully mounted between the centres using a lathe dog attached to the work piece, the bent tail of the dog fitting into the slot provided on the catch plate. If the work piece is mounted on a chuck or a face plate, care should be taken to centre it accurately with the lathe axis. The trueness of the work piece held on a chuck is tested by holding a chalk or a scriber or a dial indicator against the rotating work piece. 2) Rough turning : The rough turning is the process of removal of excess material from the work piece in a minimum time by applying high rate of feed and heavy depth of cut. The roughing cut should be so made that the machine, the tool, and the work piece can bear the load and it does not make too rough a surface and spoil the centres. The depth of cut for roughing operations in average machine shop work is form 2 to 5 mm and the rate of feed is from 0.3 to 1.5 mm per revolution of the work. In rough turning operations shown in Fig. a rough turning tool is used.

TAPERS AND TAPER TURNING A taper may be defined as a uniform increase or decrease in diameter of a piece of work measured along its length. In a lathe, taper turning means to produce a conical surface by gradual reduction in diameter from a cylindrical work piece. This

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tapering of a part has wide applications in the construction of machines. Almost all machine spindles have taper holes which receive taper shank of various tools and work holding devices. CHAMFERING Chamfering, illustrated in Fig. is, the operation of bevelling the extreme end of a work piece. This is done to remove the burrs, to protect the end of the work piece from being damaged and to have a better look. The operation may be performed after knurling, rough turning, boring, drilling or thread cutting. Chamfering is an essential operation after thread cutting so that the nut may pass freely on the threaded work piece.

Chamfering Operation THREAD CUTTING The principle of thread cutting is to produce a helical groove on a cylindrical or conical surface by feeding the tool longitudinally when the job is revolved between centres or by a chuck. The longitudinal feed should be equal to the pitch of the thread to be cut per revolution of the work piece. The lead screw of the lathe, through which the saddle receives its traversing motion, has a definite pitch. A definite ratio between the longitudinal feed and rotation of the headstock spindle should therefore be found out so that the relative speeds of rotation of the work and the lead screw will result in the cutting of a screw of the desired pitch. This is effected by change gears arranged between the spindle and the lead screw or by the change gear mechanism or feed box used in a modern lathe where it provides a wider range of feed and the speed ratio can be easily and quickly changed. Fig. illustrates the principle of thread cutting.

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FACING Facing is the operation of machining the ends of a piece of work to produce a flat surface square with the axis. This is also used to cut the work to the required length. The operation involves feeding the tool perpendicular to the axis of rotation of the work piece. a properly ground facing tool is mounted in a tool holder in the tool post. A regular turning tool may also be used for facing a large work piece. The cutting edge should be set at the same height as the centre of the work piece.

KNURLING Knurling is the process of embossing a diamond shaped pattern on the surface of a work piece. The purpose of knurling is to provide an effective gripping surface 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 1 set of hardened steel rollers in a holder with the teeth cut on their surface in a definite pattern. The tool is held 2003-04

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rigidly on the tool post and the rollers are pressed against the revolving work piece to sequeeze the metal against the multiple cutting edges, producing depressions in a regular pattern on the surface of the work piece. When a single roller is used to generate parallel grooves, the tool should be set at the centre height and perpendicular to the lathe axis. But when two rollers are used, one right hand and the other left hand, to generate crossed or diamond shaped pattern, the rollers are set at equal distance from the centre. Knurls are available in coarse, medium and fine pitches. Fig. illustrates a revolving holder with three sets of knurls. Any one set or pair may be brought into operation by revolving the unit. Knurling is done at the slowest speed available in a lathe.

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Study of DRILLING MACHINE SENSITIVE DRILLING MACHINE The sensitive drilling machine is a small machine designed for drilling small holes at high-speed in light jobs. The base of the machine may be mounted on a bench or on the floor. It consists of a vertical column, a horizontal table, a head supporting the motor and driving mechanism, and a vertical spindle for driving and rotating the drill. There is no arrangement for any automatic feed of the drill spindle. The drill is fed into the work by purely hand control. High speed and hand speed are necessary for drilling small holes. High speeds are necessary to attain required cutting speed by small diameter drill. Hand feed permits the operator to feel or sense the progress of the drill into the work, so that if the drill becomes worn out or jams on any account, the pressure on the drill maybe released immediately to prevent it from breaking. As the operator senses the cutting action, at any instant, it is called sensitive drilling machine. Sensitive drilling machines are capable of rotating drills of diameter from 1.5 to 15.5 mm. Super sensitive drilling machines are designed to drill holes as small as 0.35 mm in diameter and the machine is rotated at a high speed of 20,00 r.p.m. or above. Figure illustrates a sensitive drilling machine.

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RADIAL DRILLING MACHINE The radial drilling machine is intended for drilling medium to large and heavy workpieces. The machine consists of a heavy workpieces. The machine consist of a heavy, round, vertical column mounted on a large base. The column supports a radial arm which can be raised and lowered to accommodate workpieces of different heights. The arm may be swung around to any position over the work bed. The drill head containing mechanism for rotating and feeding the drill is mounted on a radial arm and can be moved horizontally on the guide-ways and clamped at any desired position. These three movements in a radial drilling machine when combined together permit the drill to be located at any desired point on a large workpiece for drilling the hole. When several holes are drilled on a large workpiece, the position of the arm and the drill head is altered so that the drill spindle may be moved from one position to the other after drilling the hole without altering the setting of the work. This versatility of the machine allows it to work on large workpieces. The work may be mounted on the table or when the work is very large it may be placed on the floor or in a pit. Figure illustrates a radial drilling machine.

1. Base, 2. Column, 3. Radial arm, 4. Motor for elevating the arm, 5. Elevating screw, 6. Guide ways, 7. Motor for driving the drill spindle, 8. Drill head, 9. Drill spindle, 10. Table

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study of SHAPER INTRODUCTION : The shaper is a reciprocating type of machine tool intended primarily to produce flat surfaces. These surfaces may be horizontal, vertical, or inclined. In general, the shaper can produce any surface composed of straight line elements. Modern shapers can generate contoured surface. TYPES OF SHAPERS : Shapers are classified in a number of ways depending upon the general features of design or the purpose for which they are intended. Shapers are classified under the following headings. 1. According to the type of mechanism used for giving reciprocating motion to the ram : (a) Crank type (b) Geared type (c) Hydraulic type. 2. According to the position and travel of ram : (a) Horizontal type (b) Vertical type (c) Travelling head type. 3. According to the type of design of the table : (a) Standard shaper (b) Universal shaper. 4. According to the type of cutting stroke : (a) Push type (b) Draw type. PRINCIPAL PARTS Fig. illustrates different parts of a standard shaper. Base : The base is the necessary bed or support required for all machine tools. The base may be rigidly bolted to the floor of the shop or on the bench according to the size of the machine. It is so designed that it can take up the entire load of the machine and the forces set up by the cutting tool over the work. It is made of cast iron to resist vibration and take up high compressive load.

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Parts of a standard shaper 1. Table support, 2. Table, 3.Clapper box, 4.Apron clamping bolts, 5. Downfeed hand wheel, 6. Swivel base degrre graduations, 7. Position of stroke adjustment handwheel, 8. Ram block locking handle, 9. Ram, 10. Column, 11. Driving pulley, 12. Base, 13. Feed disc, 14. Pawl mechanism, 15.. Elevating screw.

Column : The column is a box like casting mounted upon the base. It encloses the ram driving mechanism. Two accurately machined guideways are provided on the top of the column on which the ram reciprocates. The front vertical face of the column which serves as the guideways for the crossrail is also accurately machined. The lid on the left side of the column may be opened for inspection and oiling of the internal mechanism with the column. The other side of the column contains levers, handles, etc. for operating the machine. Crossrail : The crossrail is mounted on the front vertical guideways of the column. It has two parallel guideways on its top in the vertical plane that are perpendicular to the ram axis. The table may be raised or lowered to accommodate different sizes of jobs by rotating an elevating screw which causes the crossrail to slide up and down on the vertical face of the column. A horizontal cross feed screw which is fitted within the crossrail and parallel to the top guideways of the crossrail actuates the table to move in a crosswise direction. Saddle : The saddle is mounted on the crossrail which holds the table firmly on its top. Crosswise movement of the saddle by rotating the cross feed screw by hand or power causes the table to move sideways. C.O.E.& T.Akola.

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Table : The table which is bolted to the saddle receives crosswise and vertical movements from the saddle and crossrail. It is a box like casting having T-slots both on the top and sides for clamping the work. In a universal shaper the table may be swiveled on a horizontal axis and the upper part of the table may be titled up or down. In a heavier type shaper, the front face of the table is clamped with a table support to make it more rigid. Ram : The ram is the reciprocating member of the shaper. This is semi-cylindrical in form and heavily ribbed inside to make it more rigid. It slides on the accurately machined dovetail guideways on the top of the column and is connected to the reciprocating mechanism contained within the column. It houses a screwed shaft for altering the position of the ram with respect to the work and holds the tool head at the extreme forward end. Toolhead : The toolhead of a shaper holds the tool rigidly, provides vertical and angular feed movement of the tool and allows the tool to have an automatic relief during its return stroke. The vertical slide of the toolhead has a swivel base which is held on a circular seat on the ram. The swivel base is graduated in degrees, so that the vertical slide may be set perpendicular to the work surface or at any desired angle. By rotating the downfeed screw handle, the vertical slide carrying the tool executes down feed or angular feed movement while machining vertical or angular surface. The amount of feed or depth of cut may be adjusted by a micrometer dial on the top of the downfeed screw. Apron consisting of clapper box, clapper block and tool post is clamped upon the vertical slide by a screw. By releasing the clamping screw, the apron may be swiveled upon the apron swivel pin either towards left or towards right with respect to the vertical slide. This arrangement is necessary to provide relief to the tool while making vertical or angular cuts. The two vertical walls on the apron called clapper box houses the clapper block which is connected to it by means of a hinge pin. The tool post is mounted upon the clapper block. On the forward cutting stroke the clapper block fits securely to the clapper box to make a rigid tool support. On the return stroke a slight frictional drag of the tool on the work lifts the block out of the clapper box a sufficient amount preventing the tool cutting edge from dragging and

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consequent wear.

The work surface is also prevented from any damage due to

dragging. Fig. illustrates the tool head of a shaper.

CRANK AND SLOTTED LINK MECHANISM: Crank and slotted link mechanism is shown in figure. The motion or power is transmitted to the bull gear 14 through a pinion 1 which receives its motion from an individual motor of overhead line shaft through speed control mechanism. Speed of the bull gear may be changed by different combination of getting or by simply shifting the bait on this step cone pulley. The bull gear 14 is a large gear mounted within the column. Bolted to the center of the bull gear is a radial slide 16 which carries a sliding block 10 into which the crank pin 11 is fitted. Rotation of the bull gear will cause the crank pin 11 to revolve at a uniform speed. Sliding block 12 which is mounted upon the crank pin 11 is fitted within the slotted link 9. The slotted link 9 which is also known as the rocker arm is pivoted at 15 at its bottom end attached to the frame of the column. The upper end of the rocker arm is forked and connected to the ram block 8 by a pin. As the bull gear rotates causing the crank pin to rotate, the sliding block 12 fastened to the crank pin 11 will rotate on the crank pin circle, and at the same time will move up and down the slot in the slotted link 9 giving it a rocking movement which is communicated to the ram. Thus the rotory motion of the bull gear is converted to reciprocating movement of the ram.

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1. Driving pinion, 2. Ram, 3. Screwed shaft, 4. Clamping lever, 5. Handwheel for position of stroke adjustment 6,7. Bevel gears, 8. Ram block, 9. Slotted link or rocker arm, 10. Bull gear sliding block, 11. Crank pin, 12. Rocker arm sliding block, 13. Lead screw, 14. Bull gear, 15. Rocker arm pivot, 16. Bull gear slide, 17,18. Bevel gears.

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STUDY OF MILLING MACHINE INTRODUCTION: A milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter. The cutter rotates at a high speed and because of the multiple cutting edges it removes metal at a very fast rate. The machine can also hold one or more number of cutters at a time. This is why a milling machine finds wide application in production work. This is superior to other machines as regards accuracy and better surface finish, and is designed for machining a variety of tool room work.

TYPES OF MILLING MACHINE: The usual classifications according to the general design of the milling machine are: 1. Column and knee type. (a) hand milling machine. (b) Plain milling machine. (c) universal milling machine. (d) Omniversal milling machine. (e) vertical milling machine. 2. Manufacturing of fixed bed type. (a) Simplex milling machine. (b) duplex milling machine. (c) Triplex milling machine. 3. Planer type. 4. Special type. (a) rotary table milling machine. (b) drum milling machine. (c) Planetary milling machine. (d) Pantograph, profiling and tracer controlled millling machine.

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VERTICAL MILLING MACHINE: A vertical milling machine can be distinguished from a horizontal milling machine by the position of its spindle which is vertical are perpendicular to the work table.

The machine may be of plain or universal type and has all the movements of the table for proper setting and feeding the work. The spindle head which is clamped to the vertical column may be swiveled at an angle, permitting the milling cutter mounted on the spindle to work on angular surfaces. In some machines, the spindle can also be adjusted up or down relative to the work. The machine is adapted for machining grooves, slots, and flat surfaces. The end mills and face milling cutters are the usual tools mounted on the spindle. The figure illustrates a vertical milling machine.

COLUMN AND KNEE TYPE : For general shopwork the most commonly used is the column and knee type where the table is mounted on the knee casting which in turn is mounted on the vertical slides of the main column. The knee is vertically adjustable on the column so that the table can be moved up and down to accommodate work of various heights. The column and knee type milling machines are classified according to the various methods of supplying power to the table, different movements of the table and different axis of rotation of the main spindle. Figure illustrates a column and knee type milling machine.

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1. Base, 2. Elevating screw, 3. Knee, 4. Knee elevating handle, 5. Crossfeed handle, 6.Saddle, Table, 8. Front brace, 9. Arbor support, 10. Conepulley, 15. Telescopic feed shaft.

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STUDY OF GRINDING MACHINE Grinding is metal cutting operation performed by means of a rotating abrasive wheel that acts as a tool. This is used to finish work pieces, which must show a high surface quality, accuracy of shape and dimension. GRINDING MACHINES Grinding machines, according to the quality of surface finish, may be classified as: 1. Rough grinders. 2. Precision grinders. Rough grinders: Rough grinders are those grinding machines whose chief work is the removal of stock without any reference to the accuracy of the results. They are mainly of the following types: 1. Floor stands and bench grinders. 2. Portable and flexible shaft grinders. 3. Swing frame grinders. 4. Abrasive belt grinders. Precision grinders: Precision grinders are those that finish parts to very accurate dimensions. According to the type of surface generated or work done they may be classified as follows: 1. Cylindrical grinders (a) Centre-type (Plain) (b) Centre-type (Universal) (c) Centreless 2. Internal grinders (a) Chucking 2003-04

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(i) Plain (ii) Universal (b) Planetary (c) Centreless 3. Surface grinders (a) Reciprocating table (i) Horizontal spindle (ii) Vertical spindle (b)Rotating table (i) Horizontal spindle (ii) Vertical spindle 4. Tool and cutter grinders (a) Universal (b) Special 5. Special grinding machines

FLOOR-STAND AND BENCH GRINDERS The simplest type of grinder is the floor-stand grinder as shown in fig.

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A floor-stand grinder has a horizontal spindle with wheels usually at both ends and is mounted on a base or pedestal. There is provision for driving the wheel spindle by belt from motor at the rear, at floor level. Frequently the wheels are mounted directly on the motor shaft extension in which case the motor is on the top of the stand. A small size machine mounted on a bench is called bench grinder. These machines are used for snagging and off-hand grinding of tools and miscellaneous parts. Polishing wheels may be run on these grinders. Reciprocating saw (power hacksaw) Reciprocating saws are represented by power hacksaws. A power hacksaw consists of a saw frame, a means for reciprocating the saw and frame, a worktable and vise, a supporting base, and a source of power. In operation, the machine drives a blade back and forth through a work piece, pressing down on the cutting stroke and releasing the pressure on the return. The down feed force on the blade may be obtained from gravity or springs regulated by a ratchet mechanism, a positive feed screw or from a hydraulic drive. The simplest type of feed is the gravity Feed, in which the saw blade is forced into the work by the weight of the saw and frame. A hydraulic or mechanical arrangement is also incorporated for lifting the blade on the return stroke. Many are crank driven; the large ones often are hydraulically driven. The stock to be cut is held between the clamping saws. Several pieces of bar stock can be camped together and cut at the same time. Both Square and angular cuts can be made.

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MSPP

Job 1 AIM: - To prepare a job as shown in sketch of mild steel.

MATERIAL: 1) MS Bar of ( φ48 x 20 ) 50 φ x 30 mm long for mandrel. 2) MS Bar of (Bound) 30 φ x 125 mm long for gear wheel/gear teeth. Measuring Instrument: Vernier caliper, steel rule, marking block etc. precious – Instrument micrometer (O-25, 25-330 mm) Selection of Machine: 1) Cutting w/p

=

Power saw

2) Facing

=

Lathe Machine

3) Hole

=

Drilling

4) Gear cutting

=

Milling machine

Operation calculation: C.O.E.& T.Akola.

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To find out no. of teeth is to make and also depth and Index amount. Given data: Outside diameter = 1.88 inch = 48 mm Dip 1) No of teeth

= 16 British =

N

N

=

( O.D. x D.P.) – 2

=

( 1.88 x 16

=

30.08 – 2

=

28.08

=

28 teeth

)–2

2) INDEX AMOUNT: T

=

Ratio of worm wheel No of teeth

40 10 = 28 7

=

=

3 17 × 7 17

=

1

51 119

It means that, for one teeth – one complete turn and 51 holes out of 119 hole plate. OPERATION: 1) FOR GEAR

1. Cut the bar of diameter φ 50 mm x 25 mm long 2. Face both end of Job 3. Make the Job. Length 20 mm 4. Make the bar of φ 48 mm 5. Make the bar φ 20 after marking center 6. Drill the hole of φ 20 after marking center. 7. Find out no.28 teeth by calculation.

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MSPP

8. We find out 28 teeth by calculation as of (1 turn as 51/119 hole plate) on indexing plate. 9. Make the teeth proper depth and this procedure. Make 28 teeth on gear blank. 10. One by one makes teeth and by continuing this procedure we make 28 teeth on gear blank 11. These operations make gear. Precaution: -

1) Check carefully Jobs depth of gear by venire caliper. 2) Arbor should be fitted job also. 3) Lubricant is used at the cutting of gear portion. 4) Indexing is carefully handled as per calculation.

Flow Process chart (For gear measurement) II) Part name

Prepared by

Prepared by S.N.

OPERATION

Checked by TOOL USED

MACHINE USED

1.

Cut the bar of φ 50 x 25

-

Power saw

TIME

REMARK

REQUIRED 3

mm 2.

Face both end of the

Facing

3

Drills counter

15

Job (20 mm) 3.

Center both end of Job

Shank drill 4.

Make the bar φ 48 mm

R.H.turning Tool

5.

Make the bar of φ 48 x

R.H.turning Tool

10

20 mm long 6.

Chamfering the edges

√ Tool

3

Milling Cutter

5

of Job 7.

Make external of gear

C.O.E.& T.Akola.

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on the (28 teeth) 8.

Finishing the gear.

File

(Rough

5

Smooth)

Total time 74 min

Job 2 AIM: - To prepare the Job as shown in sketch MATERIALS: -

MS bar of (round shape) φ 40 x 80 mm long. INSTRUMENT: -

Vernier caliper steel rule etc. SELECTION OF MACHINE: -

1. For cutting =

Power saw

2. Facing

Lathe Machine

=

OPERATION: -

1) Cut the bar of φ 40 x 80 mm long piece. 2) Face the bar both end. 3) Make the bar of length 70 mm 4) Make the bar of φ 38 mm 2003-04

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MSPP

5) Make the turning φ 12.5 x 20 mm long from end A 6) Make the turning φ 30 x 20 mm long from end B 7) Make the taper after 20 mm from end b at initial φ 38 mm so the final φ 30 mm at the total portion of tapering 40 mm. 8) From this Job we can do following operation Facing

a) Turning b) Tapering

PRECAUTION : -

1) At the time of cutting of M.S. bar. The water drop by drop on the power saw blade. 2) The work piece is properly held in the chuck to avoid the eccentric rotation of w/p. 3) The stroke length of the total is adjusted properly. 4) Depth of cut should not be large and feed given is very slowly. 5) Always give the feed in forward stroke not in reverse stroke.

Flow – Process Chart

S.

Part name

Prepared on

Prepared by

Checked by

Operation

Tool Used

Machine Used

N.

Time

Remark

Required

1.

Cut the bar of φ 40 x 80 mm

2.

Face the both end

3.

Make the bar of length 80 mm

4.

Make the bar φ 38 mm

5.

Make the turning φ 12.5 x 20 mm

-

Power saw

3 Min

Facing Tool

Lathe M/c

5

Lathe M/c

15

R.H.turning Tool

Lathe M/c.

15

R.H.turning Tool

Lathe M/c

R.H.Turning

Lathe M/c.

15

Lathe M/c.

15

form CLA 6.

Make the turning φ 30 x 20 mm from end B

7.

Taper turning

Tool Turning Tool

Total Time – 78 min

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