On a recent thread...
I mentioned adding a free-wheeling spinner to a pin vise to allow full rotation of the object held in the vise. After writing this I realized that I hadn't yet shown an example of what I was describing.
Shown below is a pin vise that uses a 3/8" geared chuck. [Obviously for the upper end of the "pin" spectrum.] I threaded a short bit of steel to match the chuck thread and mounted that in a large file handle. I purposely left the steel long so that I could mount a length of freely-turning hex steel between the handle and the chuck. This can be held in the fingers while the other hand turns the handle to grind cylindrical objects or it can be grasped in the vise so that turning the handle presents all aspects of the workpiece for filing, grinding, polishing, etc.
It quickly became obvious that the hex spinner would benefit greatly from a handle so I added a removable handle to it. The first picture shows the components. The large nut is used as a lock nut to secure the chuck to the steel rod.
And here's what it looks like when all assembled.