A few years ago I was looking into picking up a Bridgeport Series 1 R2E4 cnc mill and and upgrading the control.

The mill came with a very large collection of quick change tool holders. I was wondering how the holders work? Are they collets or do they lock the cutter in position? (I really didn't look at them very closly at the time.)

What I was curious about was setting tool heights and weather or not the tool height was maintained between changes?

This is probably a stupid question, but I don't know, so I gotta ask.