LABORATORY MANUAL J E C GROUP OF COLLEGES

PREFACE

This laboratory is aimed at providing an introduction to the Know-how of common processes used in industries for manufacturing parts by removal of material in a controlled manner. Auxiliary methods for to desired accuracy and quality will also be covered. The emphasis throughout the laboratory course will be on understanding the basic features of the processes rather than details of constructions of machine, or common practices in manufacturing or acquiring skill in the operation of machines. Evidently, acquaintance with the machine is desirable and the laboratory sessions will provide adequate opportunity for this.

- HEAD OF DEPARTMENT

DEPARTMENT OF MECHANICAL LABORATORY MANUAL J E C GROUP OF COLLEGES INDEX

S. No. List of Experiments Page No.

1. To study of single point cutting geometry and to grind the tool asp er given 1-4 tool geometry.  2. T o study the machine, milling cutters, head sand i n d e x i n g 5-14 methods and to prepare a on milling machine.

3. T o machine a hexagonal / octagonal nut using indexing head on milling  15-18 machine.  4. To cut BSW/Metric internal threads on machine. 19-22

5. T o cut multi-start /Metric threads on lathe machine. 23-26

6.  using a boring bar in a centre lathe. 27-28

7. Study of capstan lathe and its tooling and prepare a tool layout & jobas per 29-34 given drawing.  8. Demonstration on milling machine for generation of plane surfaces anduse of 35-38 end milling cutters.  9. Grinding of milling cutters and . 39-42

10. Cylindrical grinding using grinding attachment in a centre lathe. 43-48

11. To determine the coefficient of permeability of a soil using constant head 49-54 method.

12. To study lathe machine construction and various parts including 55-64 attachments,lathe cutting speed, feed and depth of cut.

DEPARTMENT OF MECHANICAL ENGINEERING LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 1 Object Study of single point geometry and grind the tool as per given tool geometry.

Apparatus Mild Steel Job Piece, etc.

Theory Both material and geometry of the cutting tools play very important roles on their performances in achieving effectiveness, efficiency and overall economy of machining.

Tool Surfaces and Elements The design components of the cutting tool are defined as follows: Rake face is the surface over which the chip, formed in the cutting process,slides. Flank face is the surface(s) over which the surface, produced on the workpiece, passes Cutting edge is a theoretical line of intersection of the rake and the flank surfaces Cutting wedge is the tool body enclosed between the rake and the flank faces Shank is the part of the tool by which it is held Cutting tools may be classified according to the number of major cutting edges (points) involved as follows: Single point: e.g., tools, shaping, planning and slotting tools and boring tools Double (two) point: e.g., drills Multipoint (more than two): e.g., milling cutters, tools, hobs, gear shaping cutters etc.

Fig. 1.1

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The terminology used to designate the surfaces, angles and radii of single-point tools is shown below. The tool shown in Figure (a) and (b) is a single-point cutting tool, but the same definitions apply to index able tools as well.

Fig. 1.2

Figure.1.2 (A)Three views of a typical HSS (High Speed Steel tool) showing the various angles and their values with abbreviations. (b) Designations and symbols for the right-hand cutting tool with the tool signature

Terminology Face The flat surface of a single-point tool into which the workpiece rotates during a turning operation. On a typical turning set-up, the tool face is positioned upwards. Feed The rate at which the cutting tool and the workpiece move in relation to each other. For turning, “feed” is the

DEPARTMENT OF MECHANICAL ENGINEERING 02 LABORATORY MANUAL J E C GROUP OF COLLEGES rate that the single-point tool is passed along the outer surface of the rotating workpiece. Flank A flat surface of a single-point tool that is adjacent to the face of the tool. The side flank faces the direction that the tool is fed into the workpiece, and the end flank passes over the newly machined surface. Lead angle A common name for the side cutting edge angle. If a tool holder is built with dimensions that shift the angle of an insert, the lead angle takes this change into consideration. Nose radius The rounded tip on the cutting edge of a single-point tool. The greater the nose radius, the greater is the degree of roundness at the tip. A zero degree nose radius creates a sharp point. Rake angle (γ): Angle of inclination of rake surface from reference plane Clearance angle (α): Angle of inclination of clearance or flank surface from the finished surface . Positive rake – helps reduce cutting force and thus cutting power requirement. Negative rake – to increase edge-strength and life of the tool Zero rake – to simplify design and manufacture of the form tools. Clearance angle is essentially provided to avoid rubbing of the tool (flank) with the machined surface which causes loss of energy and damages of both the tool and the job surface. Hence, clearance angle is a must and must be positive (3 ~ 15 degree) depending upon tool-work materials and type of the machining operations like turning, , boring etc.)

Procedure 1. Job is fixed in hand for proper alignment. 2. Start the grinding machine and grind the job as per given specification. 3. A rough cut is used to grind the outer periphery. 4. Final grinding operation is completed in sequence. 5. The compound slide is set at the angle as per calculation and grinding operation is completed

Precautions · Work piece should be firmly gripped in the hand. · Coolant is to be used. · Hand gloves and apron must be used while working. · Proper rpm should be selected before the operation

Result Thus we successfully study the geometry of single point cutting tool and grind the single point cutting tool on the grinding tool according to the tool geometry.

Viva- Voce 1. What is single point and multi point cutting tool? 2. Explain tool geometry? 3. What is tool face and tool rake? 4. What is negative and positive rake?

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5. What is grinding and drilling?

DEPARTMENT OF MECHANICAL ENGINEERING 04 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 2 Object Study the milling machine, milling cutters, indexing heads and indexing methods.

Milling machine Introduction The milling machine removes metal with a revolving cutting tool called a . With various attachments, milling machines can be used for boring, slotting, circular milling dividing, and drilling. This machine can also be used for cutting keyways, racks and and for fluting taps and .

Types of Milling Machines Milling machines are basically classified as being horizontal or vertical to indicate the axis of the milling machine spindle. Milling operation is broadly classified as peripheral milling and face milling.

Peripheral Milling This operation is also called plain milling operation. In this operation axis of rotating tool is always kept parallel to the surface being machined. This operation is done by the cutting edges on outside periphery of the milling cutter. Different type of peripheral milling operations are possible as described below.

Slab Milling In this milling operation the cutter width extends beyond the workpiece on both sides.

Slotting It is also a type of milling operation, also called as slot milling operation. In this case width of the cutter is less than the width of workpiece. It is used to make slot in the workpiece. Thin slots can be made by using very thin milling cutters. The workpiece can be cut into two pieces by making a very thin slot throughout the depth of workpiece. Cutting the workpiece this way be slot milling is called milling.

Side Milling The cutter is used for milling of sides of a workpiece.

Straddle Milling It is just like side milling with difference that cutting (milling operation) takes place simultaneously on both the sides of workpiece.

Face Milling In the operation of face milling, axis of the milling cutter remains perpendicular to the surface being milled. In this case cutting action is done by cutting edges of both sides (end and outside) periphery of the milling cutter. Depending upon the relative geometry of workpiece and milling cutter face milling is different types as described below.

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Conventional Face Milling In this case diameter of milling cutter is greater than the width of workpiece. The milling cutter remains over hanging on both sides of workpiece.

Partial Face Milling In this case the milling cutter overhangs on the workpiece on one side only.

End Milling In case of end milling thin (low diameter) cutter are used as compared to workpiece width. It is used to make slot in the workpiece.

Knee-type Milling Machines Knee-type milling machines are characterized by a vertical adjustable worktable resting on a saddle supported by a knee. The knee is a massive casting that rides vertically on the milling machine column and can be clamped rigidly to the column in a position where the milling head and the milling machine spindle are properly adjusted vertically for operation.

Fig. 2.1

Major Components. (1) Column. (2) Knee. (3) Saddle and Swivel Table. (4) Power Feed Mechanism. (5) Table.

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(6) Spindle. (7) Over arm. (8) Arbor Support.

Milling cutters

Fig. 2.2

Types of Milling Cutters Plain Milling Cutter:It is a metal cylinder having teeth cut on its periphery for producing a flat horizontal surface.

Fig. 2.3

Metal Slitting Saw Milling Cutter: The metal slitting saw milling cutter is a very thin, plain milling cutter. It is used for metal sawing and for cutting narrow slots in metal.

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Fig. 2.4

Side Milling Cutters: Side milling cutters are plain milling cutters with the addition of teeth on one or both sides. When teeth are added to one side only, the cutter is called a half-side milling cutter and is identified as being either a right-hand or left-hand cutter. Side milling cutters are generally used for slotting and straddle milling.

Fig. 2.5

End Milling Cutters: End milling cutters have teeth on the end as well as the periphery. End milling cutters are employed in the production of slots, keyways, recesses, and tangs. They are also used for milling angles, shoulders, and the edges of work pieces.

Fig. 2.6

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Face Milling Cutter: Face milling cutters are cutters of large diameter having no shanks. They are fastened directly to the milling machine spindle with adapters. Face milling machine cutters are generally made with inserted teeth of high-speed steel or tungsten carbide in a soft steel hub.

T-Slot Milling Cutter: The T-slot milling cutter is used to machine T-slot grooves in worktables, fixtures, and other holding devices. The cutter has a plain or side milling cutter mounted to the end of a narrow shank.

Fig. 2.7

Angle Milling Cutters: The angle milling cutter has peripheral teeth which are neither parallel nor perpendicular to the cutter axis. The angle of the right or left cutter edge is usually 30, 45, or 60. Double- angle cutters have included the angles of 45, 60, and 90.

Fig. 2.8

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Concave and Convex Milling Cutters: Concave and convex milling cutters are formed tooth cutters shaped to produce concave and convex contours of one-half circle or less.

Corner-rounding Milling Cutter: The corner-rounding milling cutter is a formed tooth cutter used for milling rounded corners on work pieces up to and including one-quarter of a circle.

Fig. 2.9 Geometry of Milling Cutter

Fig. 2.10

Gear Hob:The gear hob is a formed-tooth milling cutter with helical teeth arranged like the thread on a . These teeth are fluted to produce the required cutting edges. Hobs are generally used for such work as finishing spur gears, spiral gears, and worm wheels.

Fig. 2.11

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Indexing : The index fixture consists of an index head, also called a dividing head, and a footstock, similar to the of a lathe. An index plate containing graduations is used to control the rotation of the index head spindle. The plate is fixed to the index head, and an index crank, connected to the index head spindle by a worm gear and shaft, is moved about the index plate. The sector indicates the next hole in which the pin is to be inserted and makes it unnecessary to count the holes when moving the index crank after each cut.

Fig. 2.12

Index Head: The bead of the indexing fixture contains an indexing mechanism, used to control the rotation of the index head spindle in order to space or divide a work piece accurately. A simple indexing mechanism consists of a 40-tooth worm wheel fastened to the index head spindle, a single-cut worm, a crank for turning the worm shaft, and an index plate and sector. Since there are 40 teeth in the worm wheel, one turn of the index crank causes the worm wheel, and consequently the index head spindle to, make one-fortieth of a turn; so 40 turns of the index crank revolves the spindle one full turn.

Indexing methods

Fig. 2.13

DEPARTMENT OF MECHANICAL ENGINEERING 11 LABORATORY MANUAL J E C GROUP OF COLLEGES

Direct Indexing: The construction of some index heads permits the worm to be disengaged from the worm wheel, making possible a quicker method of indexing, called direct indexing. Direct indexing is accomplished by an additional index plate fastened to the index head spindle. Direct index plates usually have 24 holes and offer a quick means of milling squares, hexagons, taps, etc. Any number of divisions which is a factor of 24 can be indexed quickly and conveniently by the direct indexing method.

Differential Indexing: Sometimes a number of divisions are required which cannot be obtained by simple indexing with the index plates regularly supplied. To obtain these divisions a differential index head is used. The index crank is connected to the worm shaft by a train of gears instead of by a direct coupling and with simple indexing.

Angular Indexing: one turn of the index crank will revolve the circumference of the work 1/40 of 360°, or 9°. To determine the number of turns, and parts of a turn of the index crank for a desired number of degrees, divide the number of degrees by 9. The quotient will represent the number of complete turns and fractions of a turn to rotate the index crank.

Apparatus Milling machine and milling setup.

Result Study of milling machine, milling cutters, indexing heads and indexing methods is done.

Viva- Voce 1. What is milling and drilling? 2. How many types of milling machine and milling cutters? 3. What is indexing head and indexing fixture?

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DEPARTMENT OF MECHANICAL ENGINEERING 14 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 3 Object Prepare a gear on milling machine.

Apparatus Milling machine , milling cutters , mild steel rod (50mm dia.)

Basic Concept Milling is the process of machining flat, curved, or irregular surfaces by feeding the work piece against a rotating cutter containing a number of cutting edges. The usual Mill consists basically of a motor driven spindle, which mounts and revolves the milling cutter, and a reciprocating adjustable worktable, which mounts and feeds the work piece.

Gear Cutting General.Gear teeth are cut on the milling machine using formed milling cutters called involute gear cutters. These cutters are manufactured in many pitch sizes and shapes for different numbers of teeth per gear (table on the following page).

Operation If involute gear cutters are not available and the teeth must be restored on gears that cannot be replaced, a lathe cutter bit can be ground to the shape of the gear tooth spaces and mounted in a fly cutter for the operation. The gear is milled in the following manner: This method of is not as accurate as using an involute gear cutter and should be used only for emergency cutting of teeth.

Table: Involute Gear Milling Cutters.

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Fig. 3.1

Procedure (i) Fasten the indexing fixture to the milling machine table. Use a to mount the gear between the index head and the footstock centers. Adjust the indexing fixture on the milling machine table, or adjust the position of the cutter, to make the gear axis perpendicular to the milling machine spindle axis. (ii) Take the cutter bit that has been ground to the shape of the gear tooth spaces and fasten it in the fly cutter arbor. Adjust the cutter centrally with the axis of the gear. Rotate the milling machine spindle to position the cutter bit in the fly cutter so that its cutting edge is down ward. (iii) Align the tooth space to be cut with the fly cutter arbor and cutter bit by turning the index

Result Prepared the gear on milling machine.

DEPARTMENT OF MECHANICAL ENGINEERING 16 LABORATORY MANUAL J E C GROUP OF COLLEGES Precautions 1. It is a good practice always to index clockwise on the plate. 2. Before setting up a job, be sure that the work piece, the table, the taper in the spindle, and arbor or cutter shank, are all clean and free from chips, nicks, or burrs. 3. Set up every job as close to the milling machine spindle as the circumstances permit. 4. Do not select a milling cutter of larger diameter than is necessary. 5. Keep milling cutters sharp at all times. 6. Do not change feeds or speeds while the milling machine is in operation. 7. Always lower the table before backing the work piece under a revolving milling cutter. 8. Feed the work piece in a direction opposite to the rotation of the milling cutter, except when milling long or deep slots or when cutting off stock. 9. Never run a milling cutter backwards. 10. When using clamps to secure the work pieces, be sure that they are tight and that the work piece is held so that it will not spring or vibrate while it is being cut. 11. Keep chips away from the work piece; brush them out of the way by any convenient means, but do not do so by hand or with waste.

Viva- Voce 1. What is gear? 2. How many type of gear? 3. What is the method of gear cutting? 4. Which metal tool is used for gearing cutting?

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DEPARTMENT OF MECHANICAL ENGINEERING 18 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 4 Object Prepare a hexagonal / octagonal nut using indexing head on milling m/c and to cut BSW/METRIC internal threads on lathe.

Indexing Indexing is the operation of dividing the periphery of a workpiece into any number of equal parts. For example if we want to make a hexagonal bolt. Head of the bolt is given hexagonal shape. We do indexing to divide circular workpiece into six equal parts and then all the six parts are milled to an identical flat surface. If we want to cut „n‟ number of teeth in a gear blank. The circumference of gear blank is divided into „n‟ number of equal parts and teeth are made by milling operation one by one. The main component used in indexing operation is universal dividing head.

Universal Dividing Head It is most popular and common type of indexing arrangement. As indicated by its name “universal”, it can be used to do all types of indexing on a milling machine. Universal dividing head can set the workpiece in vertical, horizontal, or in inclined position relative to the worktable in addition to working principle is explained below The worm gear has 40 teeth and the worm has simple thread. Crank is directly attached with the worm. If we revolve crank by 40 revolutions the spindle attached with worm gear will revolve by only one revolution and one complete turn of the crank will revolve the spindle only by 1/40th revolution (turn). In order to turn the crank precisely a fraction of a revolution, an indexing plate is used. An indexing plate is like a circular disc having concentric rings of different number of equally spaced holes. Normally indexing plate is kept stationary by a lock pin. A spring loaded pin is fixed to the crank which can be fixed into any hole of indexing plate. The turning movement of the workpiece is stably controlled by the movement of crank as explained below.

Indexing Method There are different indexing methods in popularity. These are : (a) Direct indexing (b) Simple indexing (c) Compound indexing (d) Differential indexing

Direct Indexing It is also named as rapid indexing. For this direct indexing plate is used which has 24 equally spaced holes in a circle. It is possible to divide the surface of workpiece into any number of equal divisions out of 2, 3, 4, 56, 8, 12, 24 parts. These all numbers are the factors of 24. In this case first of all worm and worm wheel is disengaged. We find number of holes by which spring loaded pin is to be moved. If we want to divide the surface into 6 parts than number of holes by which pin is to be moved 24/N for 6 parts N = 6. So number of holes =26/ 6=4 that is after completing one pair of milling whole surface of workpiece we have to move the pin by 4 holes before next milling operation, that is to be done for 5 number of times for making

DEPARTMENT OF MECHANICAL ENGINEERING 19 LABORATORY MANUAL J E C GROUP OF COLLEGES hexagonal bolt. Simple Indexing It is also named as plain indexing. It over comes the major limitation of direct indexing that is possibility of dividing circumference of work piece into some fixed Worm gear Worm piece Spindle Work carrier Change gear Driven gear Driver Worm shaft Indexing crank Spring loaded pin Indexing plate 21number of divisions. In this case worm and worm gear is first engaged. So one Milling complete turn of indexing crank revolves the work piece by 1/40th revolution. Three indexing plates are used.

Aim To machine a hexagon in the given workpiece to the dimensions as shown in the figure using Shaping Machine

Fig. 4.1

Tools Required Shaping Machine, , Divider, Steel Rule, Chalk piece, Bevel Protractor.

Procedure 1. The given workpiece is measured for its initial dimensions. 2. With the help of scriber, mark the hexagon dimensions in the workpiece. 3. Fix the workpiece in the vice of the shaping machine. 4. After fixing the workpiece and the shaping tool, allow the ram to reciprocate. 5. Start the shaping process by giving the required depth by lowering the tool. 6. Slowly increase the depth of cut and repeat the procedure to make the hexagon shape. 7. The workpiece is now checked for final dimensions.

Result Thus, a hexagon is machined in the given workpiece to the dimensions as shown in the figure using Shaping Machine.

Viva- Voce 1. What is shaping? 2. What is hexagonal and octagonal cutting? 3. How many types of indexing method?

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DEPARTMENT OF MECHANICAL ENGINEERING 22 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 5 Object To cut multi-start square / metric threads.

Apparatus Right hand tool holder with bit, turning tool, parting tool, outside spring caliper , vernier caliper ,threads caliper and steel scale etc.

Basic Concept :- Helical ridge of uniform section formed on inside or outside of cylinder or cone External thread:- Cut on external surface or cone Internal thread:- Produced on inside of cylinder or cone

Thread Terminology

Fig. 5.1

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Pitch diameter: - Diameter of imaginary cylinder that passes through thread at point where groove and thread widths are equal. Lead:- The distance a screw thread advances in one revolution.

Fig. 5.2

Root: - Bottom surface joining sides of two adjacent threads. Flank:- Thread surface that connects crest with root. Depth of thread: - Distance between crest and root measured perpendicular to axis. Angle of thread: - Included angle between sides of thread measured in axial plane. Helix angle: - Angle that thread makes with plane perpendicular to thread axis. ISO Metric Thread:- Metric threads can be identified by the letter M preceding the major thread diameter, and the pitch.

Fig. 5.3

British Standard Whitworth (BSW) Thread

Fig. 5.4

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Internal Threads:- Cutting threads in a hole. ISO Metric Thread :- Metric threads can be identified by the letter M preceding the major thread diameter, and the pitch.

Fig. 5.5

Multi-start threads have a greater lead than single-start threads of equal pitch length, but are there any other differences in function? Is there any difference in strength between a single-start The advantage of multi-start threads is simply a faster lead in a shallower form depth. This could certainly improve the stiffness, and consequently critical speed of a lead screw used for motion control. Luer components, I imagine, use the thread form because of its shallow radial depth requirements and quick connect/disconnect abilities. Operation performed on work held in or or mounted on faceplate. Threading tool similar to boring except shape ground to form of thread to be cut.

Procedure 1. Check that the machine is clean and oiled properly before starting it. 2. Hold the job in three-jaw chuck (self –centre chuck). 3. Centering the tool. 4. the one side of rod. 5. Chamfer the side of job. 6. Make the cut external metric threads on lathe m/c. 7. Meet it with the nut.

Result Prepared multi start thread as per drawing.

Viva- Voce 1. What is threading? 2. What is pitch and helix angle? 3. In bolt which thread is required?

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DEPARTMENT OF MECHANICAL ENGINEERING 26 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 6 Object Boring using a boring bar in a centre lathe.

Apparatus Material Required: Mild Steel Bar (50mm). Tools and Equipments Used: Lathe machine, Single point cutting tool, Boring Bar, Single point Boring tool.

Theory Boring Boring is the operation enlarging the diameter of the previously made hole. It is done for the following reasons. 1. To enlarge a hole by means of an adjustable cutting tool. This is done when a suitable sized is not available or the hole diameter is so large that is cannot be ordinarily drilled. 2. To finish a hole accurately and bring it to the required size 3. To machine the internal surface of the 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 independent path with respect to the hole Boring tool is a tool with only one cutting edge. The tool is held in a boring bar which has a taper shank to fit into the spindle or a socket. For perfectly finishing a hole, the job is drilled undersize slightly. Boring operation in some precise drilling machine is performed to enlarge the holes to an accuracy of 0.00125mm. The spindle speed during boring should be adjusted to be lesser than that of reaming.

Procedure 1. First of all take a work piece of 45mm of length and 50mm of diameter. 2. Perform the facing operation on either end of the work piece to reduce its length up to 40mm. 3. After doing the centering, Drilling operation is performed throughout the work piece up to 20mm diameter. 4. Then Boring operation is done to obtain the internal diameter 22.5mm.

Result

Precautions 1. The work piece should be firmly held in the chuck. 2. Centering and Boring operations should be carefully performed. 3. Depth of cut should be minimum in case of boring.

DEPARTMENT OF MECHANICAL ENGINEERING 27 LABORATORY MANUAL J E C GROUP OF COLLEGES

Fig. 5.1

Viva Voce 1. What is boring process? 2. Which type of machine use for boring? 3. Which type of tool use for boring process?

DEPARTMENT OF MECHANICAL ENGINEERING 28 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 7 Object Study of capstan lathe and its tooling and prepare a tool layout.

Basic Concept Capstan The semiautomatic lathes, capstan lathe and turret lathe are very similar in construction, operation and application. Fig. 6.1 schematically shows the basic configuration of capstan lathe.

Fig. 6.1 Schematic configuration of capstan lathe.

In contrast to centre lathes, capstan and turret lathes Ø are semiautomatic Ø possess an axially movable indexable turret (mostly hexagonal) in place of tailstock Ø holds large number of cutting tools; upto four in indexable tool post on the front slide, one in the rear slide and upto six in the turret (if hexagonal) as indicated in the schematic diagrams. Ø are more productive for quick engagement and overlapped functioning of the tools in addition to faster

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mounting and feeding of the job and rapid speed change. Ø enable repetitive production of same job requiring less involvement, effort and attention of the operator for pre-setting of work–speed and feed rate and length of travel of the cutting tools Ø are relatively costlier Ø are suitable and economically viable for batch production or small lot production. Ø There are some differences in between capstan and turret lathes such as, Ø Turret lathes are relatively more robust and heavy duty machines Ø Capstan lathes generally deal with short or long rod type blanks held in collet, whereas turret lathes mostly work on chucking type jobs held in the quick acting chucks Ø In capstan lathe, the turret travels with limited stroke length within a saddle type guide block, called auxiliary bed, which is clamped on the main bed as indicated in Fig. whereas in turret lathe. Ø Heavy turret being mounted on the saddle which directly slides with larger stroke length on the main bed as indicated in Ø One additional guide rod or pilot bar is provided on the headstock of the turret lathes, to ensure rigid axial travel of the turret head Ø External screw threads are cut in capstan lathe, if required, using a self opening die being mounted in one face of the turret, whereas in turret lathes external threads are generally cut, if required, by a single point or multipoint chasing tool being mounted on the front slide and moved by a short leads crew and a swing type half nut.

Tool layout

Fig.6.2 Basic configuration of multispindle automatic vertical lathe

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Differences between a Capstan Lathe and Turret and an Engine Lathe 1) The headstock of a turret lathe is similar to that of an engine lathe in construction but possesses wider range of speeds, and is of heavier in construction. 2) Similar sizes of capstan and turret lathe and engine lathe, when an engine lathewill require a motor of 3h.p. to drive its spindle and other parts, a capstan and turret lathe will demand power as high as 15h.p. for high rate of production. 3) In a turret lathe, the tailstock of an engine lathe is replaced by a turret. This is a six sided block each of which may carry one or more tools. These tools may be indexed one after the other to perform different operations in a regular order. This is a decisive advantage in mass production. 4) In a turret lathe, combination of cuts can be taken. Two or more tools may be mounted on the same face of the turret, making it possible to machine more than one surface at a time. This feature reduces total operational time. 5) A semiskilled operator can operate a capstan or turret lathe after the machine has been set up by a skilled . A skilled machinist may be requisitioned for setting up only for a large number of machines, where as actual production may be given by a semiskilled operator. 6) Capstan and turret lathe is fundamentally a production machine, capable of producing large number of identical pieces in a minimum time. The centre lathe is suitable for odd jobs having different shapes and sizes. 7) Capstan and turret lathes are not usually fitted with lead for cuttingthreads. A short length of lead screw called “Chasing screw “ are some times provided for cutting threads by a chaser in a turret lathe.

Aim

Tools And Equipments Required Capstan Lathe, Stopper, drill chuck, counter sink bit, , turning tool, parting off tool, Vernier Caliper.

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Procedure 1. Prepare the tooling layout for the given workpiece. 2. Set the tools in their respective positions of the tool stations. 3. The workpiece is chucked and checked for the rotation. 4. The adjustment to the length of feed for each tool is adjusted by rotating the adjustment screws. 5. Feed the tools in the required sequence to machine the given workpiece.

Result Study of capstan lathe is done.

Viva- Voce 1. What is lathe machine? 2. How many types of lathe machine? 3. Difference between capston and tarot lathe? 4. How many types of operation performed by lathe?

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DEPARTMENT OF MECHANICAL ENGINEERING 34 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 8 Object Demonstration on milling machine for generation of plane surfaces and use of end milling cutters.

Theory Definition Milling is the process of machining flat, curved or irregular surface by feeding the work piece against a rotating cutter containing a number of cutting edges

Operation The milling machine consists basically of a motor driven spindle, which mounts and revolves the milling cutter and a reciprocating adjustable worktable, which mounts and feed the work piece

Types of Milling Machines 1. Knee-type milling machine 2. Universal Horizontal milling machine 3. Ram type milling machine 4. Universal Ram type milling machine 5. Swivel cutter head ram type milling machine

Fig. 7.1

DEPARTMENT OF MECHANICAL ENGINEERING 35 LABORATORY MANUAL J E C GROUP OF COLLEGES

Milling Cutters Milling cutters are usually made of high-speed steel and are with its parts and angles identified. The types of milling cutter are been classified as follows Helical milling cutter; 2.Saw milling cutter; 3.Side milling cutter; 4.End milling cutter; 5.T slot milling cutter ; 6.Angle milling cutter

Fig. 7.2 Milling cutter type

Selection of milling cutter The selection of milling cutter can be done through the possible ways 1. High speed steel, stellite and cemented carbides have a distinct advantage of being capable of rapid production when used on a machine that can reach the proper speed. 2. The harder the material, the greater will be the heat generated in cutting. Cutter should be selected for the heat resisting properties. 3. The two side milling cutters can be used for the majority of operations

Cutting Tool Nomenclature Shown below is a self-explanatory figure of cutting tool nomenclature

Fig. 7.3

DEPARTMENT OF MECHANICAL ENGINEERING 36 LABORATORY MANUAL J E C GROUP OF COLLEGES

Calculation Feed in mm/rev = Feed per tooth (ft) X number of cutter teeth(n) Feed per min (table feed) = F = feed per rev x cutter speed in RPM(V) = ft X n X V

Result Hence, we have studied the milling machine for generation of plane surfaces and use of and milling cutters.

Viva- Voce 1. What is milling ? 2. How many types of milling machine? 3. Which operation are performed on milling machine?

DEPARTMENT OF MECHANICAL ENGINEERING 37 LABORATORY MANUAL J E C GROUP OF COLLEGES

DEPARTMENT OF MECHANICAL ENGINEERING 38 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 9 Object Grinding of milling cutters and drills.

Tool Grinding The Versa-Mil mounted on the compound rest of a lathe will duplicate the full range of tool and cutter grinding offered by conventional tool grinders. For successful results, the lathe should be in excellent operating condition and preferably small in size to permit the close setting of feeds and angles. Versa-Mil spindles use precision, spring-loaded duplex bearings to eliminate play in the for successful tool grinding. The Versa-Mil tool rest is solidly constructed to provide rigid support with a tip that is designed for smooth, solid contact under the teeth or flutes of the tool being ground. The operator familiar with tool grinding and the use of the Versa-Mil soon develops methods for grinding the various types and forms of cutters. Tool grinding cannot be completely covered in this manual, and it is suggested that reference material covering tool grinding be consulted for complete detailed instructions.

Selection of Grinding Wheels Grinding wheels should be in the medium grit range for tool and cutter grinding. The shape of the cutting tool will determine which wheel design to use. manufacturers' catalogs should be referred to for proper wheel selection.

Depth of Cut Light traversed cuts should be used to avoid overheating and burning the cutting edge of the tool. Dry grinding is recommended for sharpening high speed steel because coolant removes heat from the cutting edge too quickly causing cracking.

Direction of Wheel Rotation It is generally safer to have the wheel rotate off and away from the tool cutting edge. This allows the tooth rest to position the tooth and prevent the cutter from turning. This method, however, has some drawbacks, in that the heat from grinding is directed toward the tool cutting edge and leaves a which must be removed with an oilstone.

Down Method In this method, the rotation of the wheel is from the body of the tooth off and away from the cutting edge. The direction of wheel rotation holds the cutter on the tooth but will raise a burr on the cutting edge, which must be removed by stoning. This method has a tendency to draw temper from the metal.

DEPARTMENT OF MECHANICAL ENGINEERING 39 LABORATORY MANUAL J E C GROUP OF COLLEGES

Fig. 8.1

Up Method In this method, the wheel rotation is from the cutting edge towards the body of the tooth. With this method, there 'is less danger of burning the tooth. However, the operator must ensure that the cutter is held firmly against the tool rest. If the cutter turns during grinding, the cutter will be ruined.

Fig. 8.2

Result We have done successfully studied of grinding.

Viva- Voce 1. What is grinding? 2. What is drilling? 3. What is up method and down method for grinding?

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DEPARTMENT OF MECHANICAL ENGINEERING 41 LABORATORY MANUAL J E C GROUP OF COLLEGES

DEPARTMENT OF MECHANICAL ENGINEERING 42 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 10 Object To Study the cylindrical grinding using grinding attachment in a centre lathe.

Theory The Centre Lathe is used to manufacture cylindrical shapes from a range of materials including; steels and plastics. Many of the components that go together to make an engine work have been manufactured using lathes. These may be lathes operated directly by people (manual lathes) or computer controlled lathes (CNC machines) that have been programmed to carry out a particular task. A basic manual centre lathe is shown below. This type of lathe is controlled by a person turning the various handles on the top slide and cross slide in order to make a product / part.

Fig. 10.1

Component of Lathe Bed Bed is mounted on the legs of the lathe which are bolted to the floor. It forms the base of the machine. It is made of cast iron and its top surface is machined accurately and precisely. Headstock of the lathe is located at the extreme left of the bed and the tailstock at the right extreme. Carriage is positioned in between the headstock and tailstock and slides on the bed guide ways. The top of the bed has flat or 'V' shaped guideways. The tailstock and the carriage slides on these guideways.

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Inverted 'V' shaped guideways are useful in better guide and accurate alignment of saddle and tailstock. The metal burrs resulting from turning operation automatically fall through. Flat bed guideways can be found in older machine tools. It is useful in heavy machines handling large workpieces. But then the accuracy is not high.

Headstock Headstock is mounted permanently on the inner guideways at the left hand side of the leg bed. The headstock houses a hollow spindle and the mechanism for driving the spindle at multiple speeds. The headstock will have any of the following arrangements for driving and altering the spindle speeds (i) Stepped cone pulley drive (ii) Back gear drive (iii) All gear drive

Spindle The spindle rotates on two large bearings housed on the headstock casting. A hole extends through the spindle so that a long may be passed through the hole. The front end of the spindle is threaded on which chucks, faceplate, driving plate and catch plate are screwed. The front end of the hole is tapered to receive live center which supports the work. On the other side of the spindle, a gear known as a spindle gear is fitted. Through this gear, tumbler gears and a main gear train, the power is transmitted to the gear on the lead screw.

Tailstock Tailstock is located on the inner guideways at the right side of the bed opposite to the headstock. The body of the tailstock is bored and houses the tailstock spindle or ram. The spindle moves front and back inside the hole. The spindle has a taper hole to receive the dead centre or shanks of tools like drill or . If the tailstock handwheel is rotated in the clockwise direction, the spindle advances. The spindle will be withdrawn inside the hole, if the hand wheel is rotated in anti-clockwise direction. To remove the dead centre or any other tool from the spindle, the handwheel is rotated in anticlockwise direction further. The movement of the spindle inside the hole may be locked by operating the spindle clamp located on top of the tailstock. In order to hold workpieces of different lengths, the tailstock can be locked at any desired position on the lathe bed. Tailstock clamping bolts and clamping pates are used for this purpose. Tailstock is designed to function as two units-the base and the body. The base of the tailstock is clamped to the bed. The body is placed on the base and can be made to slide sidewards-perpendicular to the bed guideways upto a certain distance.

Carriage Carriage is located between the headstock and tailstock on the lathe bed guideways. It can be moved along the bed either towards or away from the headstock. It has several parts to support, move and control the cutting tool. The parts of the carriage are: a) saddle b) apron c) cross-slide

DEPARTMENT OF MECHANICAL ENGINEERING 44 LABORATORY MANUAL J E C GROUP OF COLLEGES d) compound rest

Cross slide Cross-slide is situated on the saddle and slides on the dovetail guideways at right angles to the bed guideways. It carries compound rest, compound slide and tool post. Cross slide handwheel is rotated to move it at right angles to the lathe axis. It can also be power driven. The cross slide hand wheel is graduated on its rim to enable to give known amount of feed as accurate as 0.05mm.

Compound rest Compound rest is a part which connects cross slide and compound slide. It is mounted on the cross-slide by tongue and groove joint. It has a circular base on which angular graduations are marked. The compound rest can be swiveled to the required angle while turning tapers. A top slide known as compound slide is attached to the compound rest by dove tail joint. The tool post is situated on the compound slide.

Tool post This is located on top of the compound slide. It is used to hold the tools rigidly. Tools are selected according to the type of operation and mounted on the tool post and adjusted to a convenient working position. There are different types of tool posts and they are: 1. Single screw tool post 2. Four bolt tool post 3. Four way tool post 4. Open side tool post

Single screw tool post The tool is held by a screw in this toolpost. It consists of a round bar with a slotted hole in the centre for fixing the tool by means of a setscrew. A concave ring and a convex rocker are used to set the height of the tool point at the right position. The tool fits on the flat top surface of the rocker. The tool post is not rigid enough for heavy works as only one clamping screw is used to clamp the tool.

Four way tool post This type of tool post can accommodate four tools at a time on the four open sides of the post. The tools are held in position by separate screws and a locking bolt is located at the centre. The required tool may be set for machining by swiveling the tool post. Machining can be completed in a shorter time because the required tools are pre-set. Ø compound slide Ø tool post

Attachments Each general purpose conventional is designed and used for a set of specific machining work on jobs of limited range of shape and size. But often some unusual work also need to be done in a specific machine tools, e.g. milling in a lathe, tapping in a drilling machine, gear teeth cutting in shaping machine and so on. Under such conditions, some special devices or systems are additionally used being mounted in the

DEPARTMENT OF MECHANICAL ENGINEERING 45 LABORATORY MANUAL J E C GROUP OF COLLEGES ordinary machine tools. Such additional special devices, which augment the processing capability of any ordinary machine tool, are known as Attachments, Unlike accessories, Attachments are not that inevitable and procured separately as and when required and obviously on extra payment. Some attachments being used in the general purpose conventional machine tools are: Ø Taper turning attachment Ø Copy turning attachments Ø Milling and cylindrical grinding attachments Ø Spherical turning attachments Ø Relieving attachment

Grinding attachment Grinding attachment is very similar to milling attachment. But in the former, there is no gear box and the spindle speed is much higher as needed for grinding operation. Such attachments are employed for external and internal cylindrical grinding, finishing grooves, splines etc. and also for finish grinding of screw threads in centre lathe. But unlike dedicated machines, attachments cannot provide high accuracy and finish.

Result To Study the cylindrical grinding using grinding attachment in a centre lathe.

Viva- Voce 1. How many types of lathe machine? 2. How much component in lathe? 3. What is cylindrical grinding?

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DEPARTMENT OF MECHANICAL ENGINEERING 47 LABORATORY MANUAL J E C GROUP OF COLLEGES

DEPARTMENT OF MECHANICAL ENGINEERING 48 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 11 OBJECTIVE To determine the coefficient of permeability of a soil using constant head method. NEED AND SCOPE

The knowledge of this property is much useful in solving problems involving yield of water bearing strata, seepage through earthen dams, stability of earthen dams, and embankments of canal bank affected by seepage, settlement etc.

PLANNING AND ORGANIZATION 1. Preparation of the soil sample for the test 2. Finding the discharge through the specimen under a particular head of water. DEFINITION OF COEFFICIENT OF PERMEABILITY The rate of flow under laminar flow conditions through a unit cross sectional are of porous medium under unit hydraulic gradient is defined as coefficient of permeability. Permeability : It is a measure of the ease in which water can flow through a soil volume. It is one of the most important geotechnical parameters. However, it is probably the most difficult parameter to determine. In large part, it controls the strength and deformation behavior of soils. It directly affects the following: • quantity of water that will flow toward an excavation • design of cutoffs beneath dams on permeable foundations • design of the clay layer for a landfill liner. For fine grained soil Falling head permeability test is done, whereas constant head permeability test is done for the coarse grained soil. Applications: • Estimation of quantity of underground seepage water under various hydraulic conditions • Quantification of water during pumping for underground construction • Stability analysis of slopes, earth dams, and earth retaining structures • Design of landfill liner EQUIPMENTS: COMBINATION PERMEAMETER ASSEMBLY, STOP WATCH, GRADUATED CYLINDER (250 OR

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500 ML)BALANCE SENSITIVE TO 0.01 LB, MOISTURE CANS, DRYING OVEN, THERMOMETER 1. Permeameter mould of non-corrodible material having a capacity of 1000 ml, with an internal diameter of 100 0.1 mm and internal effective height of 127.3� 0.1 mm. 2. The mould shall be fitted with a detachable base plate and removable extension counter. 3. Compacting equipment: 50 mm diameter circular face, weight 2.76 kg and height of fall 310 mm as specified in I.S 2720 part VII 1965. 4. Drainage bade: A bade with a porous disc, 12 mm thick which has the permeability 10 times the expected permeability of soil. 5. Drainage cap: A porous disc of 12 mm thick having a fitting for connection to water inlet or outlet. 6. Constant head tank: A suitable water reservoir capable of supplying water to the permeameter under constant head. 7. Graduated glass cylinder to receive the discharge. 8. Stop watch to note the time. 9. A meter scale to measure the head differences and length of specimen.

PREPARATION OF SPECIMEN FOR TESTING A. UNDISTURBED SOIL SAMPLE 1. Note down the sample number, bore hole number and its depth at which the sample was taken. 2. Remove the protective cover (paraffin wax) from the sampling tube. 3. Place the sampling tube in the sample extraction frame, and push the plunger to get a cylindrical form sample not longer than 35 mm in diameter and having height equal to that of mould. 4. The specimen shall be placed centrally over the porous disc to the drainage base. 5. The angular space shall be filled with an impervious material such as cement slurry or wax, to provide sealing between the soil specimen and the mould against leakage from the sides. 6. The drainage cap shall then be fixed over the top of the mould. 7. Now the specimen is ready for the test.

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DISTURBED SOIL SAMPLE 1. A 2.5 kg sample shall be taken from a thoroughly mixed air dried or oven dried material. 2. The initial moisture content of the 2.5 kg sample shall be determined. Then the soil shall be placed in the air tight container. 3. Add required quantity of water to get the desired moisture content. 4. Mix the soil thoroughly. 5. Weigh the empty permeameter mould. 6. After greasing the inside slightly, clamp it between the compaction base plate and extension collar. 7. Place the assembly on a solid base and fill it with sample and compact it. 8. After completion of a compaction the collar and excess soil are removed. 9. Find the weight of mould with sample. 10. Place the mould with sample in the permeameter, with drainage base and cap having discs that are properly saturated.

TEST PROCEDURE 1. For the constant head arrangement, the specimen shall be connected through the top inlet to the constant head reservoir. 2. Open the bottom outlet. 3. Establish steady flow of water. 4. The quantity of flow for a convenient time interval may be collected. 5. Repeat three times for the same interval.

OBSERVATION AND RECORDING The flow is very low at the beginning, gradually increases and then stands constant. Constant head permeability test is suitable for cohesionless soils. For cohesive soils falling head method is suitable.

COMPUTATION Coefficient of permeability for a constant head test is given by

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Presentation of data The coefficient of permeability is reported in cm/sec at 27o C. The dry density, the void ratio and the degree of saturation shall be reported.The test results should be given as below: Details of sample Diameter of specimen ..cm Length of specimen(L) ..cm Area of specimen (A) ..cm2

Specific gravity of soil Gs .. Volume of specimen (V) ..cm3

Weight of dry specimen (Ws) .gm Moisture content .%

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Interpretation and Reporting

Result

VIVA VOCE: 1. Define permeability. 2. Define coefficient of permeability. 3. What are the applications of permeability ? 4. What are the factors that affect the permeability in the soil ?

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DEPARTMENT OF MECHANICAL ENGINEERING 54 LABORATORY MANUAL J E C GROUP OF COLLEGES Experiment No. 12 OBJECTIVE To study lathe machine construction and various parts including attachments,lathe tools cutting speed, feed and depth of cut.

INTRODUCTION Lathe is one of the most versatile and widely used machine tools all over the world. It is commonly known as the mother of all other machine tool. The main function of a lathe is to remove metal from a job to give it the required shape and size. The job is secure1y and rigidly held in the chuck or in between centers on the lathe machine and then turn it against a single point cutting tool which will remove metal from the job in the form of chips. An engine lathe is the most basic and simplest form of the lathe. It derives its name from the early lathes, which obtained their power from engines. Besides the simple turning operation as described above, lathe can be used to carry out other operations also, such as drilling, reaming, boring, taper turning, knurling, screw thread cutting, grinding etc.

TYPES OF LATHE Lathes are manufactured in a variety of types and sizes, from very small bench lathes used for precision work to huge lathes used for turning large steel shafts. But the principle of operation and function of all types of lathes is same. The different types of lathes are: 1. Speed lathe: (a) Wood working (b) Spinning (c) Centering (d) Polishing 2. Centre or engine lathe: (a) Be1t drive (b) Individual motor drive (c) Gear head lathe 3. Bench lathe 4. Tool room Lathe 5. Capstan and Turret lathe 6. Special purpose lathe (a) Whee1 lathe (b) Gap bed lathe (c) Dup1icating lathe

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(d) T-lathe

7. Some of common lathes are described as under. Speed Lathe Speed lathe is simplest of all types of lathes in construction and operation. The important parts of speed lathe are following- (1) Bed (2) Headstock (3) Tailstock, and (4) Tool post mounted on an adjustable slide. It has no feed box, lead screw or conventional type of carriage. The tool is mounted on the adjustable slide and is fed into the work by hand contro1. The speed lathe finds applications where cutting force is least such as in wood working, spinning, centering, polishing, winding, buffing etc. This lathe has been so named because of the very high speed of the headstock spindle.

Centre Lathe or Engine Lathe The term “engine” is associated with this lathe due to the fact that in the very early days of its development it was driven by steam engine. This lathe is the important member of the lathe family and is the most widely used. Similar to the speed lathe, the engine lathe has all the basic parts, e.g., bed, headstock, and tailstock. But its headstock is much more robust in construction and contains additional mechanism for driving the lathe spindle at multiple speeds.

Bench Lathe This is a small lathe usually mounted on a bench. It has practically all the parts of an engine lathe or speed lathe and it performs almost all the operations. This is used for small and precision work.

Tool Room Lathe This lathe has features similar to an engine lathe but it is much more accurately built. It has a wide range of spindle speeds ranging from a very low to a quite high speed up to 2500 rpm. This lathe is mainly used for precision work on tools, dies, gauges and in machining work where accuracy is needed.

Capstan and Turret Lathe The development of these 1athes results from the technological advancement of the engine lathe and these are vastly used for mass production work. The distinguishing feature of this type of lathe is that the tailstock of an engine lathe is replaced by a hexagonal turret, on the face of which multiple tools may be fitted and fed into the work in proper sequence.

Special Purpose Lathes These lathes are constructed for special purposes and for jobs, which cannot be accommodated or conveniently machined on a standard lathe. The gap bed lathe, in which a section of the bed adjacent to the headstock is removable, is used to swing extra-large-diameter pieces. The T-lathe is used for machining of rotors for jet engines. The bed of this lathe has T-shape. Duplicating lathe is one for duplicating the shape of a flat or round template on to the job.

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Automatic Lathes These lathes are so designed that all the working and job handling movements of the complete manufacturing process for a job are done automatically. These are high speed, heavy duty, mass production lathes with complete automatic control.

CONSTRUCTION OF LATHE MACHINE A simple lathe comprises of a bed made of grey cast iron on which headstock, tailstock, carriage and other components of lathe are mounted. Fig. shows the different parts of engine lathe or central lathe. The major parts of lathe machine are given as under: 1. Bed 2. Head stock 3. Tailstock 4. Carriage 5. Feed mechanism 6. Thread cutting mechanism

1.BED:

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The bed of a lathe machine is the base on which all other parts of lathe are mounted. It is massive and rigid single piece casting made to support other active parts of lathe. On left end of the bed, headstock of lathe machine is located while on right side tailstock is located. The carriage of the machine rests over the bed and slides on it. On the top of the bed there are two sets of guideways-innerways and outerways.The innerways provide sliding surfaces for the tailstock and the outerways for the carriage.The guideways of the lathe bed may be flat and inverted V shape. Generally cast iron alloyed with nickel and chromium material is used for manufacturing of the lathe bed.

2. HEAD STOCK: The main function of headstock is to transmit power to the different parts of a lathe. It comprises of the headstock casting to accommodate all the parts within it including gear train arrangement. The main spindle is adjusted in it, which possesses live centre to which the work can be attached. It supports the work and revolves with the work, fitted into the main spindle of the headstock. The cone pulley is also attached with this arrangement, which is used to get various spindle speed through electric motor.

3. TAIL STOCK: It is commonly used for the objective of primarily giving an outer bearing and support the circular job being turned on centers. Tailstock can be easily set or adjusted for alignment or non-alignment with respect to the spindle centre and carries a centre called dead centre for supporting one end of the work. Both live and dead centers have 60° conical points to fit centre holes in the circular job, the other end tapering to allow for good fitting into the spindles.

4. CARRIAGE Carriage is mounted on the outer guide ways of lathe bed and it can move in a direction parallel to the spindle axis. It comprises of important parts such as apron, cross-slide, saddle, compound rest, and tool post. The lower part of the carriage is termed the apron in which there are gears to constitute apron mechanism for adjusting the direction of the feed using clutch mechanism and the split half nut for automatic feed. The cross-slide is basically mounted on the carriage, which generally travels at right angles to the spindle axis. On the cross-slide, a saddle is mounted in which the compound rest is adjusted which can rotate and fix to any desired angle. The compound rest slide is actuated by a screw, which rotates in a nut fixed to the saddle.The tool post is an important part of carriage,which fits in a tee-slot in the compound rest and holds the tool holder in place by the tool post screw.

5. FEED MECHANISM Feed mechanism is the combination of different units through which motion of headstock spindle is transmitted to the carriage of lathe machine. Following units play role in feed mechanism of a lathe machine- 1. End of bed gearing 2. Feed gear box 3. Lead screw and feed rod 4. Apron mechanism The gearing at the end of bed transmits the rotary motion of headstock spindle to the feed gear box. Through the feed gear box the motion is further transmitted either to the feed shaft or lead screw, depending on whether the lathe machine is being used for plain turning or screw cutting. The feed

DEPARTMENT OF MECHANICAL ENGINEERING 58 LABORATORY MANUAL J E C GROUP OF COLLEGES gear box contains a number of different sizes of gears. The feed gear box provides a means to alter the rate of feed, and the ration between revolutions of the headstock spindle and the movement of carriage for thread cutting by changing the speed of rotation of the feed rod or lead screw.The apron is fitted to the saddle. It contains gears and clutches to transmit motion from the feed rod to the carriage, and the half nut which engages with the lead screw during cutting threads.

6. THREAD CUTTING MECHANISM The half nut or split nut is used for thread cutting in a lathe. It engages or disengages the carriage with the lead screw so that the rotation of the lead screw is used to traverse the tool along the workpiece to cut screw threads. The direction in which the carriage moves depends upon the position of the feed reverse lever on the headstock.

ACCESSORIES AND ATTACHMENTS OF LATHE There are many lathe accessories provided by the lathe manufacturer along with the lathe, which support the lathe operations. The important lathe accessories include centers, catch plates and carriers, chucks, , face plates, angle plates, , and rests. These are used either for holding and supporting the work or for holding the tool. Attachments are additional equipments provided by the lathe manufacturer along with the lathe, which can be used for specific operations.

Lathe centers The most common method of holding the job in a lathe is between the two centers generally known as live centre (head stock centre) and dead centre (tailstock centre). They are made of very hard materials to resist deflection and wear and they are used to hold and support the cylindrical jobs.

Carriers or driving dog and catch plates These are used to drive a job when it is held between two centers. Carriers or driving dogs are attached to the end of the job by a setscrew. Catch plates are either screwed or bolted to the nose of the headstock spindle. A projecting pin from the catch plate or carrier fits into the slot provided in either of them. This imparts a positive drive between the lathe spindle and job.

Chucks Chuck is one of the most important devices for holding and rotating a job in a lathe. It is basically attached to the headstock spindle of the lathe. The internal threads in the chuck fit on to the external threads on the spindle nose. Short, cylindrical, hol1ow objects or those of irregular shapes, which cannot be conveniently mounted between centers, are easily and rigidly held in a chuck. Jobs of short length and large diameter or of irregular shape, which cannot be conveniently mounted between centers, are held quickly and rigidly in a chuck. There are a number of types of lathe chucks, e.g. (1) Three jaws or universal (2) Four jaw independent chuck (3) Magnetic chuck (4) Collet chuck (5) Air or hydraulic chuck operated chuck (6) Combination chuck (7) Drill chuck.

DEPARTMENT OF MECHANICAL ENGINEERING 59 LABORATORY MANUAL J E C GROUP OF COLLEGES

Face plates Face plates are employed for holding jobs, which cannot be conveniently held between centers or by chucks. A face plate possesses the radial, plain and T slots for holding jobs or work-pieces by bolts and clamps. Face plates consist of a circular disc bored out and threaded to fit the nose of the lathe spindle. They are heavily constructed and have strong thick ribs on the back. They have slots cut into them, therefore nuts, bolts, clamps and angles are used to hold the jobs on the face plate. They are accurately machined and ground.

Angle plates is a cast iron plate having two faces machined to make them absolutely at right angles to each other. Holes and slots are provided on both faces so that it may be clamped on a faceplate and can hold the job or workpiece on the other face by bolts and clamps. The plates are used in conjunction with a face plate when the holding surface of the job should be kept horizontal.

Mandrels A mandrel is a device used for holding and rotating a hollow job that has been previously drilled or bored. The job revolves with the mandrel, which is mounted between two centers. It is rotated by the and the catch plate and it drives the work by friction. Different types of mandrels are employed according to specific requirements. It is hardened and tempered steel shaft or bar with 60° centers, so that it can be mounted between centers. It holds and locates a part from its center hole. The mandrel is always rotated with the help of a lathe dog; it is never placed in a chuck for turning the job. A mandrel unlike an arbor is a job holding device rather than a cutting tool holder. A bush can be faced and turned by holding the same on a mandrel between centers. It is generally used in order to machine the entire length of a hollow job.

Rests A rest is a lathe device, which supports a long slender job, when it is turned between centers or by a chuck, at some intermediate point to prevent bending of the job due to its own weight and vibration set up due to the cutting force that acts on it. The two types of rests commonly used for supporting a long job in an engine lathe are the steady or centre rest and the follower rest.

LATHE OPERATIONS For performing the various machining operations in a lathe, the job is being supported and driven by anyone of the following methods. 1. Job is held and driven by chuck with the other end supported on the tail stock centre. 2. Job is held between centers and driven by carriers and catch plates. 3. Job is held on a mandrel, which is supported between centers and driven by carriers and catch plates. 4. Job is held and driven by a chuck or a faceplate or an angle plate. The above methods for holding the job can be classified under two headings namely job held between centers and job held by a chuck or any other fixture.

(a) Operations, which can be performed in a lathe either by holding the workpiece between centers or by a chuck are: 1. Straight turning 2. Shoulder turning 3. Taper turning 4. Chamfering

DEPARTMENT OF MECHANICAL ENGINEERING 60 LABORATORY MANUAL J E C GROUP OF COLLEGES

5. Eccentric turning 6. Thread cutting 7. Facing 8. 9. Filing 10. Polishing 11. Grooving 12. Knurling 13. Spinning 14. Spring winding

(b) Operations which are performed by holding the work by a chuck or a faceplate or an angle plate are: 1. Undercutting 2. Parting-off 3. Internal thread cutting 4. Drilling 5. Reaming 6. Boring 7. Counter boring 8. Taper boring 9.Tapping

Cutting Speed (V): It is the speed at which the metal is removed by the cutting tool from the workpiece. In case of lathe machine cutting speed is the peripheral speed of the work past the cutting tool. It is expressed in meter/min. or mm/min.

Cutting speed (V) = π DN/60 × 1000 mm/min Where, D = diameter of the workpiece (mm) N = rpm of the work

Cutting speed depends upon the following factors: i. Tool material. ii. Work material. iii. Depth of cut. iv. Tool geometry. v. Type of machine tool. vi. Surface quality required.

Feed (f): It is the relative motion of tool in one revolution of workpiece. It is expressed in mm/rev.

Depth of Cut (t): It is the total amount of metal removed per pass of the cutting tool. It is expressed in mm. It can vary and depending upon the type of tool and work material. Mathematically, it is half of difference of diameters.

Depth of cut (t) = D-d/2 mm where, D = outer diameter, (mm) d = Inner diameter (mm)

DEPARTMENT OF MECHANICAL ENGINEERING 61 LABORATORY MANUAL J E C GROUP OF COLLEGES

RESULT

VIVA- VOCE: 1. Define Lathe machine. 2. What is the working principal of a lathe machine? 3. Explain the types of lathe machine. 4. What are the major parts of a lathe machine? 5. Explain the lathe accessories & attachments of lathe. 6. Explain the operations performed in a lathe machine. 7. Define cutting speed, feed & depth of cut.

DEPARTMENT OF MECHANICAL ENGINEERING 62 LABORATORY MANUAL J E C GROUP OF COLLEGES

DEPARTMENT OF MECHANICAL ENGINEERING 63 LABORATORY MANUAL J E C GROUP OF COLLEGES

DEPARTMENT OF MECHANICAL ENGINEERING 64 LABORATORY MANUAL J E C GROUP OF COLLEGES NAME OF THE LBORATORY:______CODE:______

SEMESTER:______NAME OF STUDENT:______ROLL No:______

LAB PERFORMANCE APPRAISAL SHEET Marks Awarded for Date of Experiment No & Full Lab Viva-Voce Lab Total (X) Signature of Allotment Title of the Experiment Marks (Y) Performance Citizenship Lab In charge with Date

Total Marks from experiment No------to ----- (Z) Total marks as per syllabus (M)= Z / 10

Note: Lab citizenship covers Discipline, Punctuality, Lab Meeting Participation, Note book Record Keeping and contribution in up keeping of the lab

DEPARTMENT OF MECHANICAL ENGINEERING LABORATORY MANUAL J E C GROUP OF COLLEGES Note

DEPARTMENT OF MECHANICAL ENGINEERING LABORATORY MANUAL J E C GROUP OF COLLEGES Note

DEPARTMENT OF MECHANICAL ENGINEERING LABORATORY MANUAL J E C GROUP OF COLLEGES Note

DEPARTMENT OF MECHANICAL ENGINEERING