[sanddrag]

Originally Posted by Chris is me

You install a collet on a lathe or mill to secure parts, as opposed to something like a three jaw chuck. The cone shape of the collet squeezes the work piece in place as it is tightened into the lathe or mill.

I'd think a hex collet would probably be used on a lathe. Can't see much utility in replacing your mill's tooling with a spinning hex shaft.

The idea is to place a collet in a hexagonal shaped collet holder, which is then placed in a mill vise. This lets you index the work piece to six accurate positions for milling the sides of the hex into round stock, without the need for a dividing head or indexer.