Lathe Machine

LATHE MACHINE

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 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.

LATHE COMPONENTS 1. Bed: Usually made of cast iron. Provides a heavy rigid frame in 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 time. 6. Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part

being machined. Chuck allows the mounting of difficult work pieces 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 work pieces. 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 circulate 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 work piece with c center, or to hold tools for drilling, reaming, thread or cutting tapers. It can be adjusted in position along the ways to accommodate different length work pieces. 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:

1. A saddle that mates with and slides along the ways. 2. An apron that controls the feed mechanisms. 3. A cross slide that controls transverse motion of the tool (toward or away from the operator). 4. A tool compound that adjusts to permit angular tool movement. 5. A tool post T-slot that holds the tool post.

MACHINING OPERATIONS:

FACING Facing is the machining of the end surfaces and shoulders of a work piece. In addition to squaring the ends of the work, facing provides a way to cut work to length accurately. Generally, only lightly cuts are required since the work will gave been cut to approximate length or rough machined to the shoulder. TURNING Turning is the machining of excess stock from the periphery of the work piece to reduce the diameter. In most of the lathe machine operations requires 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 work piece. PARTING

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.

LATHE SAFETY: 1. Do not attempt to operate a lathe until you know the proper procedures and have been checked out on its safe operation by your instructor. 2. Never attempt to operate a lathe while your senses are impaired by medication or other substances. 3. Dress appropriately! Remove any necklaces or other dangling jewelry, wristwatch, or rings. Secure any loose-fitting clothing and roll up long sleeves. Wear an apron or a properly fitted shop coat. Safety glasses are a Must! 4. Clamp all work solidly. Use the correct size tool and work-holding device for the job. Get help when handling large sections of metal, heavy chucks and attachments. 5. Check work frequently when it is being machined between centers. A work piece expands as it heats up from friction and could damage the tailstock center. 6. Be sure all guards are in place before attempting to operate the machine. Never attempt to defeat or bypass a safety switch. 7. Turn the faceplate or chuck by hand to be sure there is no binding or danger of the work striking any part of the lathe.

8. Keep the machine clear of tools, and always stop the machine before making measurements and adjustments. 9. Metal chips are sharp and can cause severe cuts. Do not try to remove them with your hands when they become “stringy” and build up on the tool post. Stop the machine and remove them with pliers. 10. Do not permit small-diameter work to project too far from the chuck without support from the tailstock. Without support, the work will be tapered or worse, spring up over the cutting tool and / or break. 11. Do not run the cutting tool into the chuck. 12. Stop the machine before attempting to wipe down its surface, so the cloth doesn’t become caught on rotating parts. When knurling, keep the coolant brush clear of the work. 13. Before repositioning or removing work from the lathe, move the cutting tool clear of the work area. 14. Avoid talking to anyone while running the lathe! Do not permit anyone to fool around with the machine while you are operating it. You are the only one who should turn the machine on or off, or make any adjustments. 15. Always remove the key form the chuck. 16. Tools must not be placed on the lathe ways. Use a tool board or place them on the lathe tray. 17. When doing filing on a lathe, make sure the file has a securely fitting handle. 18. If any odd sounding noise or vibration develops during lathe operation, stop the machine immediately. If you cannot locate the trouble get help from your instructor. 19. Remove sharp edges and burrs from the work piece before dismounting it from the machine. Burrs and sharp edges can cause painful cuts. 20. Use care when cleaning the lathe. Chips sometimes stick in recesses. Remove them with a paintbrush or wooden stick, not a dust brush.