SELF- RELEASING MANDREL HANDLE

摘要

There have been lathe mandrel handle designs published before, but as far as is known, none use the draw bolt to both engage and disengage the handle from the mandrel. The design presented here aims to correct that deficiency. Following a disastrous attempt to screwcut under power, it became obvious that a lathe mandrel handle was required so that screw threads could be cut, albeit slowly and with much winding of the handle. The first design (and the subsequent re-designs) leaned heavily on Stan Bray's design in his book Useful Workshop Tools, (Workshop Practice Series No.31) but discarded the dog clutch arrangement in favour of a clamping arrangement on to the expander tube. This worked well except that in order to remove it from the lathe, it proved necessary to use a hammer on the end of the drawbar to release the cone. This was thought to be somewhat unsatisfactory due to the shock loading being transmitted via the mandrel bearings. Following attempts to improve the design, which only succeeded in going backwards, the original clamping arrangement was abandoned in favour of the design presented here which enables the operator to use the drawbar (expander) bolt to both tighten, and release the expander cone, thus keeping the forces within the mandrel handle and away from the lathe bearings.