A lathe center, sometimes called a center, is one of the important parts inside a lathe. It is a tool that has been ground to a point to accurately position a workpiece on an axis. Usually, the lathe centers are used in the form with a 60° angle, only when it meets the situation of using on machines would apply a 75° angle. The lathe center would be inserted into a matching cylindrical deep hole drilled by a center drill.
The main task of the lathe center is to ensure the production of concentric work, which can also ensure that the accuracy would not be lowered during the transfer of the workpieces between machining or inspecting operations. Keeping the concentricity is extremely important because the workpieces or parts which complete the progress of hardening and tempering would be ground between centers in the cylindrical grinder.
Also, the lathe center can be used to support longer workpieces. If there are no supports for them, the workpieces might be deflected too much by the cutting forces, and then lower the finish and accuracy of the workpiece, or even lead to hazardous situations that put operators in danger. The lathe center can be used where a centered workpiece may be used, which may include setups in dividing heads, cylindrical grinders, tool, and cutter grinders, or other related equipment.
● Dead Center
The dead center cannot turn freely, can be used to support the workpieces at either the fixed or rotating end of the lathe machine. Usually, the dead center would produce friction between the workpiece and the center because of the rotation of the workpieces. To prevent this, lubrication is necessary to apply between the center and workpiece for preventing friction welding. Moreover, inserting a little blade on the tip of the center top will also help to reduce the friction and allow faster speed.
Dead centers are typically fully hardened to prevent damage to the important mating surfaces of the taper and to keep its 60° angle of the nose. A dead center is usually made by tungsten carbide since it is much harder than steel. Moreover, it is able to provide greater wear resistance than a steel center. When turning between centers, the dead center would be used in the headstock as well as the tailstock.
● Soft Center
The soft center is a kind of specially designed dead center. Its nose is unhardened so that it can be machined to the correct angle prior to usage. This specially designed dead center is applied to the headstock center for ensuring the center's axis is aligned with the spindle's axis.
● Revolving Center
A revolving center also called a rotating center or running center is a kind of live center. It runs in its own bearings with the 60° center rotating angle and is used at the non-driven or tailstock end of a machine. A revolving center, as a kind of live center, can be designed hard or soft.
This live center can provide larger clamping pressure and a higher rotating speed without lubrication. The revolving center is almost the dedicated style for CNC lathes while they can also be used for general machining operations as well. Spring-loaded centers are designed to compensate for center variations, and would not damage the workpieces or center tip. This is for the purpose of ensuring constant tension while machining.
● Pipe Center
Pipe center, as known as a bullnose center, is another type of live center. It is special that its diameter on the conical nose is larger than a sharp point which allows it to be used in the bore of a pipe or other workpiece with a large interior diameter that cannot use a normal pointed center. Features of the pipe center are able to ensure the workpiece remains concentric, supports the workpiece securely, and deals with workpieces with larger inner diameter.
● Cup Center
Cup centers can be designed into two types according to their functions, one is used for woodworking, the other is for metalworking. The cup center for woodworking is one of the variations of the live center. Its central point is just like a normal live center, and also gets a ring surrounding it. This ring contains the function of supporting the softer material around the center point and preventing the breaking of the wooden workpieces under the pressure from the central point.
The cup center for metalworking provides the workpiece a tapered hole rather than a conical point. Moreover, it would support the workpieces by making contact with the outside diameter of its end rather than using a center hole.
● Drive Center
A Drive center, as known as a grip center, which consists of the dead center surrounded by hardened teeth, is used in the driving end of a machine. It is usually used in machining softer workpieces like wood or soft materials. Since it can bite into soft workpieces, it can be driven directly by the center and work on the workpieces.
● Spring Center
Spring center, a member of the metalworking lathe center, is used for maintaining cutting tools. It consists of a point backed by a spring that can push the cutting tools into the workpiece.
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