Exactly.

I've been the proud possessor of four pin chucks for 20+ years which I doubt I've ever used. I've always found easier ways of holding the workpiece although the link Vic has put up is interesting.

The size of the pin is in direct correlation to the overall size of the chuck and I would have thought an eighth is fine for the tool in the link.

I have 2 x inch and a half chucks with three eighth pins and 2 x one inch chucks without pins but would take quarter inch. My pins had sprung ball bearings to hold them in place. My pin chucks are for holding bowl blanks rather than longer, between-centre items.

I have little use for these things so PM me if you might be interested in adding to your tool collection – or if you want pictures etc.

I have created an album called Pin chucks – have a look. They look pretty ropey having lived undisturbed under my workbench since the mid 1990s and my photography is well down to the same standard! Hope it's of some use and I look forward to seeing how you get on.