1 A usually tapered or cylindrical axle, spindle, or arbor inserted into a hole in a piece of work to support it during machining; A metal bar that serves as a core around which material (as metal) may be cast, molded, forged, bent, or otherwise shaped
2. The shaft and bearings on which a tool (as a circular saw) is mounted
3. Axle of a circular saw.
4. Spindle supporting work in lathe, etc.