On Fri, 17 Apr 2015 09:30:48 -0500, F. George McDuffee
wrote:

On Thu, 16 Apr 2015 11:04:10 -0700, wrote:


I need to put an o-ring groove in the underside of 500 1/4-20 flathead
screws.
snip
Might be overkill. What sort of pressures are involved?
What are you sealing? Was a flat rubber/elastomer
(urethane?) washer evaluated? How about a combination seal
and retaining compound like RTV or Loctite?

If the O-ring groove is mandatory, how about a hollow mill?
with the correct geometry? Given the problems in holding/
handling you might be better off making the complete screw
from bar stock, although slotting the head may be a
challenge. Do you have a CNC with a bar puller? How long is
the thread? Style of head/drive?
Greetings George,
I already know how to hold and locate the screw. It will take
approximately 4 seconds to remove one screw and put another in the
collet. What I really want to know is if my way of finding the radii
of the walls of the groove is one correct way.
Eric