Found in one of the publications I get:

Replace the stock setup with a 1/2"x20 threaded rod (the quill stop rod
on a Bridgeport mill) and get 2 Bridgeport-compatible "speed nut" quill
stops that are available from machine shop supply sources like MCS and
ENCO. The speed nut's quick release button allows it to slide free of
the threads for instant repositioning. With 50 marks evenly spaced
around the nuts circumference, and 20 teeth per inch on the rod, it is
precisely adjustable to .001".

Hope this is of use.

Jim

Leon wrote:


2. An easier and quicker to adjust quill dept adjustment, perhaps the push
button and spin variety vs. the two nut design. I hate spinning 2 nuts up
to 3" and that would be even worse with my next #3 item below.