Merriam-Webster Collegiate Dictionary - mandrel

 also mandril  noun  Etymology: Medieval Latin maundrellus, probably ultimately from Old Occitan mandre kingpin  Date: 1554  1.  a. a usually tapered or cylindrical axle, spindle, or arbor inserted into a hole in a piece of work to support it during machining  b. 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