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- 1. Basic Mechanical Engineering By NitinG Shekapure Unit IV Machine Tools (L24 To 28) N itin Shekapure
- 2. By: Nitin Shekapure UnitIV Machine Tools Basic Elements, Working Principle, Types of Operations with block diagram: Lathe Machine - Centre Lathe, Drilling Machines, Grinding Machines. N itin Shekapure
- 3. Lathe Machine • Latheis 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 (Work piece) to give it the required shape and size. N itin Shekapure
- 4. Working Principal LatheMachine • The job (work piece) is securely 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. N itin Shekapure
- 5. Types of Lathe Speed Lathe Engine Lathe Bench Lathe Tool room lathe Capstan and Turret Lathe CNC Lathe (Automatic Lathe) N itin Shekapure
- 6. Speed Lathe Speed latheis 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, Leadscrew or conventional type of carriage. The tool is mounted on the adjustable slide and is fed into the work by hand control. 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. N itin Shekapure
- 7. Engine Lathe (CentreLathe) 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. Centre lathes or engine lathes are classified according to methods of transmitting power to the machine. The power may be transmitted by means of belt, electric motor or through gears. N itin Shekapure
- 8. Speed Lathe This isa 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. N itin Shekapure
- 9. Tool Room Lathe Thislathe 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. N itin Shekapure
- 10. Capstan and TurretLathe The development of these lathes 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. Due to this arrangement, several different types of operations can be done on a job without re-setting of work or tools, and a number of identical parts can be produced in the minimum time. N itin Shekapure
- 11. These lathes areso 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. CNC Lathe N itin Shekapure
- 12. CONSTRUCTION OF LATHEMACHINE A simple lathe comprises of a bed made of grey cast iron on which headstock, tailstock, carriage and other components of lathe are mounted. Figure 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 N itin Shekapure
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- 14. Major Parts ofLathe Machine Bed 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. N itin Shekapure
- 15. It is usedto support all the elements and to withstand cutting forces during the operation. Bed Function: Major Parts of Lathe Machine N itin Shekapure
- 16. Head Stock The mainfunction 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. The back gear arrangement is used for obtaining a wide range of slower speeds. Some gears called change wheels are used to produce different velocity ratio required for thread cutting. Major Parts of Lathe Machine N itin Shekapure
- 17. • To supportthe spindle • To carry driving mechanism for the work-piece • To give multiple speeds to the spindle Function: Head Stock Major Parts of Lathe Machine N itin Shekapure
- 18. Tail Stock Figure showsthe tail stock of central lathe, which is commonly used for the objective of primarily giving an outer bearing and support the circular job being turned on centers. Tail stock 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. The dead centre can be mounted in ball bearing so that it rotates with the job avoiding friction of the job with dead centre as it important to hold heavy jobs. Major Parts of Lathe Machine N itin Shekapure
- 19. Function: Tail Stock MajorParts of Lathe Machine • To support the other part of the workpiece when it is being machined • To hold the tool to perform operations like drilling, reaming etc. N itin Shekapure
- 20. Carriage Carriage is mountedon 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. Major Parts of Lathe Machine N itin Shekapure
- 21. Major Parts ofLathe Machine • To support, guide, and feed the tool against the workpiece during the operation Function: Carriage N itin Shekapure
- 22. Feed Mechanism Major Partsof Lathe Machine The movement of the tool relative to the workpiece is known as feed. The lathe tool can have longitudinal, cross, and angular feed. The feed mech. has various units through which motion is transmitted from the headstock spindle to the carriage. Function: • It is used to transmit the motion from headstock spindle to the carriage. N itin Shekapure
- 23. Thread Cutting Mechanism Thehalf 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 leadscrew 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. In other times, it is disengaged and remained stationary Major Parts of Lathe Machine N itin Shekapure
- 24. Lead Screw • VeryImportant part of Lathe • Long threaded shaft driven by feed drive • Provides mechanized/automatic motion to carriage for screw threads on the job • Lead Screw is MUST for Threading Operations on Lathe • Split Nut or Half Nut Mechanism converts rotary motion of lead screw to linear motion of carriage N itin Shekapure
- 25. Specification of Lathe Thesize of a lathe is generally specified by the following means: a) Swing or maximum diameter that can be rotated over the bed ways b) Maximum length of the job that can be held between head stock and tail stock centres c) Bed length, which may include head stock length also d) Maximum diameter of the bar that can pass through spindle or collect chuck of capstan lathe. N itin Shekapure
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- 27. Lathe Machine Parts– Functions N itin Shekapure
- 28. Lathe Operations The variousoperations that can be performed on a lathe are: 1. Turning 2. Eccentric turning 3. Taper turning 4. Thread cutting 5. Facing. 6. Knurling 7. Chamfering. 8. Parting off 9. Grooving 10. Drilling 11. Boring N itin Shekapure
- 29. Turning • Most basicoperation done on lathe machine • Job or work piece is turned (rotated) using rotary motion of spindle, hence lathe is also called Turning Machine! • Lathe operator is called “Turner”! • Removal of material from a cylindrical work-piece or job • To reduce diameter of cylindrical job • Tool motion parallel to the axis of lathe • Tool used is called “Turning Tool” and it is “Single Point Cutting Tool” • Rough turning, using roughing tool or knife tool • Finish turning using finishing tool N itin Shekapure
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- 31. Eccentric Turning • Toreduce diameter of about an axis offset from axis of job • Turned portion remains eccentric to the rest of work piece • Four jaw chuck is used to hold the job • Axis of job is kept offset to the axis of lathe during turning operation N itin Shekapure
- 32. Taper Turning • Toreduce diameter of work piece uniformly along the length of work piece • Taper turning using “form tool” • Taper turning by “tailstock set over” method • Taper turning using “taper turning attachment” • Taper turning by “swiveling the compound rest” N itin Shekapure
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- 35. Facing • Removal ofmaterial from end surface of the work piece or job • To have a reference plane to mark and measure the step lengths of work • To have a face at right angle to the axis of the work • To reduce length of job • To maintain the total length of the work • Facing Tool is used • Tool motion is perpendicular to axis of lathe • To produce flat surface (especially after parting off operations) N itin Shekapure
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- 37. • Process ofbeveling the sharp edges of work piece • Chamfered jobs avoids injuries to hands of persons handling the job • Provides aesthetic look to the work piece • Chamfering tool is used to permit easy assembly of mating parts • Chamfer specified as CH 2 x 45 (2 mm deep at an angle of 45 degrees) Chamfering N itin Shekapure
- 38. Grooving or GrooveCutting • To create narrow groove on cylindrical work piece • Shape of tool is replicated as shape of groove • Operation also known as Form Turning! • Square Groove, Round Groove and ‘V’ Type Grooves N itin Shekapure
- 39. Parting • Process ofcutting work piece into 2 parts • Extension of grooving operation where feed is provided till axis of work piece • Care needs to be taken when work piece splits into two parts N itin Shekapure
- 40. Knurling • Process ofembossing a diamond shaped regular pattern on the surface of job • Tool used is called “Knurling Tool” • Types: Parallel or Straight Knurling, Diamond or Criss-Cross Knurling, Concave or Convex Knurling • Squeezing metal into peaks and valleys using plastic deformation • Provides non-slip grip to the job • Aesthetic or Decorative look N itin Shekapure
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- 42. Drilling • Process ofmaking a circular hole in cylindrical job • Tailstock is used to hold cutting tool which is called as “Drill” • Drill is feed against rotating job by rotating hand wheel of tailstock in clockwise direction • After making hole, the drill is withdrawn by rotating the tailstock handle in anti-clockwise direction N itin Shekapure
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- 44. • Process ofenlarging already existing hole in the job • Tailstock is used to hold the tool • Skill of operator plays imp role • Tool used is called as “Boring Tool” Boring N itin Shekapure
- 45. Threading or ThreadCutting • Process of creating threads in the form of helical groove on the surface of cylindrical job • Tool used is called “Thread Cutting Tool” • Point geometry of thread cutting tool creates desired type of thread. • Tool motion is parallel to axis of lathe • For 1 revolution of job, tool travels automatically by distance equal to the pitch of the thread • Fixed relation between rotary motion of job and linear motion of tool is achieved by engaging carriage with lead screw using half-nut or split-nut mechanism N itin Shekapure
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- 47. Two components canbe connected to each other with the help of nuts and bolts, the cylindrical holes need to be made in the components. DRILLING • Its the process of making the cylindrical hole in the work piece. • Drilling is the operation of producing circular hole in the work-piece by using a rotating cutter called DRILL. • The machine used for drilling is called drilling machine. Drilling Machine N itin Shekapure
- 48. Types of drillingmachine 1. Portable drilling machine 2. Sensitive or bench drilling machine 3. Upright drilling machine 4. Radial drilling machine 5. Gang drilling machine 6. Multi-spindle drilling machine 7. Deep hole drilling machine 8. Automatic drilling machine N itin Shekapure
- 49. Principal and operation •In drilling machine work piece is firmly clamped. • The cutting tool drill is fitted in to the spindle of the drilling machine. • Spindle and drill rotate at the desired speed. • The rotating drill removes the material from the work piece in the form of chips, so as to produce the cylindrical hole N itin Shekapure
- 50. Basic elements Base: lowermost part that supports the entire structure. Worktable: it is mounted on the column, it has two types of motion: Up and down and the swing about the axis of the column it supports the work piece. Spindle: it provides the rotary motion. Drilling head: it is mounted on the top of column. It contains drive mechanism and feed mechanism. Drive mechanism : it mainly consists of electric motor and gear box ,it is used for driving the spindle(drill) Feed mech: it is used for feeding the spindle against the work piece ,it can be power or hand feed. N itin Shekapure
- 51. • Drilling: processof making cylindrical hole. • Boring: process of enlarging the existing hole to meet the required size and finish, drilling larger diameter holes, boring tool is used. • Spot facing: process of enlarging and making a smooth furnished hole, it is similar to that if counter boring except in spot facing the depth of the enlarged hole is very small it is used to provide a seat for the washer. • Counter sinking: counter sink is the conical hole drilled in the work piece to accommodate the flat head screw, rivets to be fitted in the hole, process of champering the entrance of a drilled hole. • Tapping: Process of cutting internal threads with a thread tool called as tap. Types of operation N itin Shekapure
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- 55. Pillar or uprightdrilling machine • It is used for medium duty works. • It is used for drilling holes up to 75mm in diam. • Spindle is driven by electric motor through gear drive as it provides wide range of spindle speeds. • Up and down motion of the work table is controlled by lead screw • According to the depth of hole to be drilled the worktable is moved in Up and down direction. N itin Shekapure
- 56. Precautions for Drillingmachine • Lubrication is important to remove heat and friction. • Machines should be cleaned after use • Chips should be removed using brush. • T-slots, grooves, spindles sleeves, belts, pulley should be cleaned. • Machines should be lightly oiled to prevent from rusting N itin Shekapure
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- 58. Grinding • Grinding isa surface finishing operation where very thin layer of material is removed in the form of dust particles. • Thickness of material removed is in range of 0.25 to 0.50 mm. • Tool used is a abrasive wheel. N itin Shekapure
- 59. Abrasives • Abrasive isthe material employed for sharpening, grinding and polishing operations. • Natural abrasive – emery, corundum, quartz, sandstone, diamond, etc. • Artificial abrasive – carborundum, aloxite, alundum, etc. N itin Shekapure
- 60. Applications of abrasives Corundum:is a natural mineral which consists of aluminium oxide. Hardest natural substance after diamond Used for shaping, finishing and polishing other tools Emery: natural abrasive consisting of aluminium oxide and little amount of iron oxide Silicon carbide: synthetic abrasive harder than aluminium oxide Used to grind metals like iron, brass and soft bronze Used in non metals like wood and leather industries N itin Shekapure
- 61. • Zirconia aluminia:it is a mixture of zirconium oxide and aluminium oxide – Used in casting and foundry industries • Cubic boron nitride: is made up of boron nitride with a cubic crystalline structure – Used for hard coating material Applications of abrasives N itin Shekapure
- 62. Grinding Machine Grinding machineis a power operated machine tool where, the work piece is fed against constantly rotating abrasive wheel to remove thin layer of material from work. N itin Shekapure
- 63. Principle of grindingmachines • Work piece is fed against the rotating abrasive wheel. • Due to action of rubbing or friction between the abrasive particles and work piece material is removed. N itin Shekapure
- 64. Classification of grindingmachine • Bench grinding machine • Surface grinding machine • Cylindrical grinding machine • Center less grinding machine • Internal grinding machine • Special purpose grinding machine N itin Shekapure
- 65. Surface grinding machine •It is machine basically used to grind flat surface • Job is mounted to a table which moves longitudinally as well as in transverse direction • Manual feed or power feed • Work piece can clamped in two ways – Manual clamps – Magnetic chuck N itin Shekapure
- 66. Working • Work pieceis clamped to the table by operating magnetic chuck. • Required grade of grinding tool is fixed to spindle. • Grinding operation is carried out be operating both table traverse wheel and vertical feed hand wheel. N itin Shekapure
- 67. Cylindrical grinding machine •It is a process of grinding curved surfaces. • Surface may be straight or tapered. • Work piece is mounted on two centers, one is tailstock centre and the other is headstock centre. • Head stock center may or may not revolve. N itin Shekapure
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- 69. Centre less grindingmachine • It is used to grind curved surface work piece which are long and slender. • Work piece rests on a work-rest blade and is backed by a second wheel called as regulating wheel. • Grinding wheel pushes the work piece down the work-rest blade against the regulating wheel. N itin Shekapure
- 70. Centre less grindingmachine N itin Shekapure
- 71. Cutting terminology • Speed: it is the peripheral speed of the work piece per unit time. (m/min) • Feed : it is the distance travelled by the tool during each revolution of the work piece. (mm/revolution). • Depth of cut : it is the perpendicular distance measured from the original surface to the machined surface of the work piece. (mm) N itin Shekapure