12855451 Practical 7 Lathe Machine
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CWIT, PUNE Engineering
SUBJECT- General
Practical 7: MACHINE TOOLS Introduction: Lathe machine was invented in 1740. Even today, though this lathe operates with the help of motor, it is known as Engine lathe. Various attachments and accessories are used with the lathe machine. The worker working on lathe machine, i.e. the operator of lathe is called as Turner because on lathe machine many operations such as plain turning, facing, taper turning, drilling, reaming, tapping, boring, knurling, screw cutting etc are carried out.
Figure showing LATHE MACHINE LATHE COMPONENTS: 1. Bed:
Usually made of cast iron. Provides a heavy rigid frame on which all the main components are mounted. 2. Ways: Inner and outer guide rails that are precision machined parallel to assure accuracy of movement. 3. Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it rotates the work. 4. Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving levers. 5. Spindle: Hole through the headstock to which bar stock can be fed, which allows shafts that are up to 2 times the length between lathe centers to be worked on one end at a time. DEPARTMENT OF MECHANICAL ENGINEERING
Page 1
CWIT, PUNE Engineering
SUBJECT- General
6. Chuck:
3-jaw (self centering) or 4-jaw (independent) to clamp part being machined. Chuck: allows the mounting of difficult workpieces that are not round, square or triangular. 7. Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it. 8. Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools. 9. Cross Slide: Mounted on the traverse slide of the carriage, and uses a hand wheel to feed tools into the workpiece. 10.Tool Post: To mount tool holders in which the cutting bits are clamped 11.Compound Rest: Mounted to the cross slide, it pivots around the tool post. 12.Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide. 13.Lead Screw: For cutting threads. The purpose of a lathe is to rotate a part against a tool whose position it controls. It is useful for fabricating parts and/or features that have a circular cross section. The spindle is the part of the lathe that rotates. Various work holding attachments such as three jaw chucks, collets, and centers can be held in the spindle. The spindle is driven by an electric motor through a system of belt drives and/or gear trains. Spindle speed is controlled by varying the geometry of the drive train. The tailstock can be used to support the end of the workpiece with a center, or to hold tools for drilling, reaming, threading, or cutting tapers. It can be adjusted in position along the ways to accommodate different length workpieces. The ram can be fed along the axis of rotation with the tailstock hand wheel. The carriage controls and supports the cutting tool. It consists of: • A saddle that mates with and slides along the ways. • An apron that controls the feed mechanisms. • A cross slide that controls transverse motion of the tool (toward or away from the operator). • A tool compound that adjusts to permit angular tool movement. • A tool post T-slot that holds the tool post.
DEPARTMENT OF MECHANICAL ENGINEERING
Page 2
CWIT, PUNE Engineering
SUBJECT- General
Lathe tool posts Machining operations: FACING Facing is the machining of the end surfaces and shoulders of a workpiece. In addition to squaring the ends of the work, facing provides a way to cut work to length accurately. Generally, only light cuts are required since the work will have been cut to approximate length or rough machined to the shoulder. TURNING Turning is the machining of excess stock from the periphery of the workpiece to reduce the diameter. In most lathe machining operations requiring removal of large amounts of stock, a series of roughing cuts is taken to remove most of the excess stock Then a finishing cut is taken to accurately “size” the workpiece. PARTING DEPARTMENT OF MECHANICAL ENGINEERING
Page 3
CWIT, PUNE Engineering
SUBJECT- General
A parting tool is deeper and narrower than a turning tool. It is designed for making narrow grooves and for cutting off parts. DRILLING A lathe can also be used to drill holes accurately concentric with the centerline of a cylindrical part. BORING Boring is an operation in which a hole is enlarged with a single point cutting tool. A boring bar is used to support the cutting tool as it extends into the hole. Because of the extension of the boring bar, the tool is supported less rigidly and is more likely to chatter. This can be corrected by using slower spindle speeds or by grinding a smaller radius on the nose of the tool SAFETY PRECAUTIONS In machining operations, always keep safety in mind, no matter how important the job is or how well you know the machine you are operating. Listed here are some safety precautions that you MUST follow: 1. Before starting any lathe operations, always prepare yourself by rolling up your shirt sleeves and removing your watch, rings, and other jewelry that might become caught while you operate the machine. 2. Wear goggles or an approved face shield at all times whenever you operate a lathe or when you are near a lathe that is being operated. 3. Be sure the work area is clear of obstructions that you might fall or trip over. 4. Keep the deck area around your machine clear of oil or grease to prevent the possibility of slipping or falling into the machine. 5. Always use assistance when handling large workpieces or large chucks. 6. NEVER remove chips with your bare hands. Use a stick or brush, and always stop the machine. 7. Always secure power to the machine when you take measurements or make adjustments to the chuck. 8. Be attentive, not only to the operation of your machine, but also to events going on around it. NEVER permit skylarking in the area. 9. Should it become necessary to operate the lathe while the ship is underway, be especially safety conscious. (Machines should be operated ONLY in relatively calm seas.) DEPARTMENT OF MECHANICAL ENGINEERING
Page 4
CWIT, PUNE Engineering
SUBJECT- General
10. Be alert to the location of the cutting tool while you take measurements or make adjustments. 11. Always observe the specific safety precautions posted for the machine you are operating.
DEPARTMENT OF MECHANICAL ENGINEERING
Page 5
SUBJECT- General
Practical 7: MACHINE TOOLS Introduction: Lathe machine was invented in 1740. Even today, though this lathe operates with the help of motor, it is known as Engine lathe. Various attachments and accessories are used with the lathe machine. The worker working on lathe machine, i.e. the operator of lathe is called as Turner because on lathe machine many operations such as plain turning, facing, taper turning, drilling, reaming, tapping, boring, knurling, screw cutting etc are carried out.
Figure showing LATHE MACHINE LATHE COMPONENTS: 1. Bed:
Usually made of cast iron. Provides a heavy rigid frame on which all the main components are mounted. 2. Ways: Inner and outer guide rails that are precision machined parallel to assure accuracy of movement. 3. Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it rotates the work. 4. Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving levers. 5. Spindle: Hole through the headstock to which bar stock can be fed, which allows shafts that are up to 2 times the length between lathe centers to be worked on one end at a time. DEPARTMENT OF MECHANICAL ENGINEERING
Page 1
CWIT, PUNE Engineering
SUBJECT- General
6. Chuck:
3-jaw (self centering) or 4-jaw (independent) to clamp part being machined. Chuck: allows the mounting of difficult workpieces that are not round, square or triangular. 7. Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it. 8. Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools. 9. Cross Slide: Mounted on the traverse slide of the carriage, and uses a hand wheel to feed tools into the workpiece. 10.Tool Post: To mount tool holders in which the cutting bits are clamped 11.Compound Rest: Mounted to the cross slide, it pivots around the tool post. 12.Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide. 13.Lead Screw: For cutting threads. The purpose of a lathe is to rotate a part against a tool whose position it controls. It is useful for fabricating parts and/or features that have a circular cross section. The spindle is the part of the lathe that rotates. Various work holding attachments such as three jaw chucks, collets, and centers can be held in the spindle. The spindle is driven by an electric motor through a system of belt drives and/or gear trains. Spindle speed is controlled by varying the geometry of the drive train. The tailstock can be used to support the end of the workpiece with a center, or to hold tools for drilling, reaming, threading, or cutting tapers. It can be adjusted in position along the ways to accommodate different length workpieces. The ram can be fed along the axis of rotation with the tailstock hand wheel. The carriage controls and supports the cutting tool. It consists of: • A saddle that mates with and slides along the ways. • An apron that controls the feed mechanisms. • A cross slide that controls transverse motion of the tool (toward or away from the operator). • A tool compound that adjusts to permit angular tool movement. • A tool post T-slot that holds the tool post.
DEPARTMENT OF MECHANICAL ENGINEERING
Page 2
CWIT, PUNE Engineering
SUBJECT- General
Lathe tool posts Machining operations: FACING Facing is the machining of the end surfaces and shoulders of a workpiece. In addition to squaring the ends of the work, facing provides a way to cut work to length accurately. Generally, only light cuts are required since the work will have been cut to approximate length or rough machined to the shoulder. TURNING Turning is the machining of excess stock from the periphery of the workpiece to reduce the diameter. In most lathe machining operations requiring removal of large amounts of stock, a series of roughing cuts is taken to remove most of the excess stock Then a finishing cut is taken to accurately “size” the workpiece. PARTING DEPARTMENT OF MECHANICAL ENGINEERING
Page 3
CWIT, PUNE Engineering
SUBJECT- General
A parting tool is deeper and narrower than a turning tool. It is designed for making narrow grooves and for cutting off parts. DRILLING A lathe can also be used to drill holes accurately concentric with the centerline of a cylindrical part. BORING Boring is an operation in which a hole is enlarged with a single point cutting tool. A boring bar is used to support the cutting tool as it extends into the hole. Because of the extension of the boring bar, the tool is supported less rigidly and is more likely to chatter. This can be corrected by using slower spindle speeds or by grinding a smaller radius on the nose of the tool SAFETY PRECAUTIONS In machining operations, always keep safety in mind, no matter how important the job is or how well you know the machine you are operating. Listed here are some safety precautions that you MUST follow: 1. Before starting any lathe operations, always prepare yourself by rolling up your shirt sleeves and removing your watch, rings, and other jewelry that might become caught while you operate the machine. 2. Wear goggles or an approved face shield at all times whenever you operate a lathe or when you are near a lathe that is being operated. 3. Be sure the work area is clear of obstructions that you might fall or trip over. 4. Keep the deck area around your machine clear of oil or grease to prevent the possibility of slipping or falling into the machine. 5. Always use assistance when handling large workpieces or large chucks. 6. NEVER remove chips with your bare hands. Use a stick or brush, and always stop the machine. 7. Always secure power to the machine when you take measurements or make adjustments to the chuck. 8. Be attentive, not only to the operation of your machine, but also to events going on around it. NEVER permit skylarking in the area. 9. Should it become necessary to operate the lathe while the ship is underway, be especially safety conscious. (Machines should be operated ONLY in relatively calm seas.) DEPARTMENT OF MECHANICAL ENGINEERING
Page 4
CWIT, PUNE Engineering
SUBJECT- General
10. Be alert to the location of the cutting tool while you take measurements or make adjustments. 11. Always observe the specific safety precautions posted for the machine you are operating.
DEPARTMENT OF MECHANICAL ENGINEERING
Page 5
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