I've been looking for some handles for some wire picks I'm making, and came across this little device while searching for "pin vice".
http://www.widgetsupply.com/page/WS/PRO ... vise/BCX13
It's a pin vice with spring loaded rotary handle. The spring is meant to retract the handle to the rest position. The handle is pushed forward to spin the head, and slid back to repeat.
I'm wondering if a little modification to this device could make it a formidable plug spinner. Put the spring behind the handle, pull back and release, allowing it to snap forward and spin quickly. Any thoughts?