It is particularly useful when cutting threads on a lathe using a tap or die held in a holder placed in the tailstock. It is used whenever a very slow, controlled, rotation is needed. It should never be used under power.
Alternative names are: Mandrel handle, Threading handle.
There is not much new in my design - there are many other examples available online. However, I was quite pleased with the use of a large coach bolt as the axle for the wooden handle - the domed-end looks very neat and the threaded fixing method is very rigid. Also, the large aluminium knob works very well (mainly by luck) because when using the device, it does not need any tools (like a spanner or allen key). Also, when releasing the device, the knob is big enough to hit with the heel of your hand to release the wedge - again, no tool is needed.
This Instructable shows the basic design idea which was governed by the materials I had to hand! The main elements are in mild steel. The Instructable steps are in the same order as I made it:
The main mandrel
The axle for the handle
The wooden handle
It was pretty simple to make. I'm still a real novice on the lathe and there was little precision in the manufacture, but the end result is very useful.