Wednesday, January 5, 2011
LATHE MACHINE
DEFINATION:
A lathe is a machine tool which spins the workpiece to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.
Introduction:
Lathes were developed as early as the 15th century and were known as "bow"
lathes. The operator rotated the workpiece by drawing a bow back and forth,either by hand or with the use of a foot treadle. Next came Bessons lathe
in 1568, which was driven by a cord passing over a pulley above the machine.
This in turn drove two other pulleys on the same shaft which rotated the
workpiece and a crude, wooden lead screw, which in turn allowed the operator
to remove metal from the piece being machined. The screw cutting lathe
originates in the 17th century. Development and advancements have continued
and today we have sophisticated computerized controlled lathes.
Lathes have allowed man to reshape, machine and manufacture many precision
cylindrical components made of various types of metal, wood, plastics, and
other materials. Without the lathe, man would still be trying to produce
cylindrical components.
Boring:
Boring is an operation to enlarge and finish holes accurately. This may be done on a lathe or a milling machine. Boring is a machine operation in which the work is in contact with a single point tool.
A work piece may be held in a 3, 4, or 6 jaw chuck and collets.
Broaching:
Broaching is an operBroaching can be done on both internal and external surfaces.ation that completes the cutting in one stroke or cut. The teeth of a broaching tool are equally spaced so that as the tool advances into the workpiece, each tooth removes a specified amount of metal.
Drilling:
Drilling is an economical way of removing large amounts of metal to create semi-precision round hole or cavity. Drilling allows a person to make holes through boards, metals, and other materials.
Used for last removal of stock on preparation for other operations like boring, reaming, or tapping.
Drill press:
A machine designed to hold drill bits which will produce cylindrical holes. Used for producing cylindrical holes, as well as reaming, boring, counter-boring, counter-sinking, honing, lapping and tapping
There are three major types:
- Sensitive drill (light drilling)
- Upright drill (heavy duty drilling)
- Radial arm drill press (large, heavy workpieces)
Facing:Facing is a lathe operation in which the cutting tool removes metal from the end of the workpiece or a shoulder. Facing is a machine operation where the work is rotated against a single point tool. A workpiece may be held in a 3, 4, or 6 jaw chuck, collets or a faceplate.
Grinding:
Grinding is an operation in which the cutting is done by the use of abrasive particles. Grinding processes remove very small chips in very large numbers by cutting the action of many small individual abrasive grains. The abrasive grains are formed into a grinding wheel.Very smooth surfaces can be accomplished by the use of the proper grinding wheel.
Honing:Honing is an internal cutting technique that uses abrasives on a rotating tool to produce extremely accurate holes that require a very smooth finish. Similar to lapping where abrasive sticks are mounted in a rotating tool.
Capable of accuracies of less than 1/10,000th of one inch.
Non-precision grinding:
Non-precision grinding is a cutting technique used when the grinding does not need to be accurate.
Non-precision grinding is done when accuracy is not important. Non-precision grinding is a free-hand operation done on a pedestal or bench grinder.
Precision grinding:
Precision grinding is a cutting technique used when close tolerances and very smooth finishes are required. Precision grinding as often used as a finish machining process. Precision grinding allows very small amounts of material to be removed from a workpiece. This is extremely useful in acquiring smooth fnishes.
Reaming:
Reaming is a sizing operation that removes a small amount of metal from a hole already drilled. The reamer is the tool used for this operation.
Shaping:
Shaping is an operation used to produce flat surfaces. When the cutting tool reciprocates while the work is fed towards the tool removing material on each stroke, it is called shaping.
Single point threading:Single point threading is a lathe operation used for creating internal / external precision machined threads with a single point tool. Uses a special cutting tool that reflects the thread form.
There are over 100 thread forms.
Tapping:
Tapping is the process of cutting a thread inside a hole so that a cap screw or bolt can be threaded into the hole. Also, it is used to make threads on nuts. Tapping is done with a tool called a "Tap".
Tapping may be done by:
- hand
- lathe machine
- milling machine
- tapping machine
Turning:
Turning is a lathe operation in which the cutting tool removes metal from the outside diameter of a workpieceA single point tool is used for turning. A workpiece may be held in a 3, 4, or 6 jaw chuck, collets or may also be held between centers.
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