On Thu, 09 Mar 2006 11:52:51 -0500, GD
wrote:

I have a Bosch router that has both a 1/4 and 1/2 inch collet. I would
like to able to use 3/16 diameter tools and wondered if the collets are
a common one for machinery and if so what are they?
Thanks
GD

Do what everyone else does, use a reducing bushing. They are
available from the places that sell routerbits, but most shops make
their own.
Take a piece of 9/16 stock turn the OD to .500 and drill the ID to
..187. Put one slit though the side and you are done. We used to slit
through the whole diameter but three quarters of the length. Turn it
over, rotate 90 degrees and slit again. This theoretically gives you
more even compression, but I've never noticed a difference.

Doesn't really need to be hardened

Will