When using multiple bit in a Foredom, we often have to deal with different shaft sizes – the usual 3/32 inch burs, the larger 1/8 inch shaft sizes and of course the many different sizes of twist drills. For some reason, I really dislike having to turn the key multiple times to open or close the jaws of the handpiece chuck.
So I have two ways to speed up the task. For opening up the jaws, I just remember “four”, the number of turns I have to make to open the chuck just enough for the 3/32 bur shaft size to the larger 1/8 bur shaft size.
For closing the jaws around a smaller shaft, there’s a neat trick. Hold the new bit in the center of the open jaws of the chuck, put your thumb lightly onto the outer toothed collar of the chuck, and gently start up the Foredom. As the chuck turns, it will naturally tighten the jaws around the bur shaft or the drill bit. Then all you have to do is a final tightening with the key.