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A lathe center, often shortened to center, is a tool that has been ground to a point to accurately position a workpiece on an axis. They usually have an included angle of 60°, but in heavy machining situations an angle of 75° is used.[1]
The primary use of a center is to ensure concentric work is produced; this allows the workpiece to be transferred between machining (or inspection) operations without any loss of accuracy. A part may be turned in a lathe, sent off for hardening and tempering and then ground between centers in a cylindrical grinder. The preservation of concentricity between the turning and grinding operations is crucial for quality work.
When turning between centers, a steady rest can be used to support longer workpieces where the cutting forces would deflect the work excessively, reducing the finish and accuracy of the workpiece, or creating a hazardous situation.
A lathe center has applications anywhere that a centered workpiece may be used; this is not limited to lathe usage but may include setups in dividing heads, cylindrical grinders, tool and cutter grinders or other related equipment. The term between centers refers to any machining operation where the job needs to be performed using centers.
A center is inserted into a matching hole drilled by a center drill. The hole is conical near the surface and cylindrical as it gets deeper.
- ^ International library of technology: Drilling; Lathe work; Boring-mill work; Working chilled iron; Bench, vise, and floor work; Erecting, vol. 138, International Textbook, 1914, p. 21.