Chuck used in cutting multistart threads - has magnetic locking pins withdrawn to allow rotation of chuck

摘要

A chuck (12) for holding a workpiece (24) whilst cutting a multi-start thread is mounted on bearings (15, 16) on the support (14). The chuck (12) is locked to the support by spring loaded pins (35) which engage slots in the locking ring (36). There are as many equally spaced pins as there are starts of the thread being cut. The pins have caps (27) of magnetic material so that they can be withdrawn by the electro-magnets after each start of the thread has been cut so that the chuck can be rotated through the required angle ready for cutting the next start.