On Thu, 16 Apr 2015 20:50:32 -0400, "Jim Wilkins"
wrote:


"Bob Engelhardt" wrote in message
...
On 4/16/2015 2:04 PM, wrote:
All-
I need to put an o-ring groove in the underside of 500 1/4-20
flathead
screws. So I need to make a groove tool to do the job. A straight
groove tool won't work because the sides of the groove are curved.
I
have made tools like this before but this is a small one and I'm
machining 304 SS so I need carbide and only want to make the tool
once. So I think to find out what radii to grind the sides of the
tool
can be determined by drawing the screw head with the groove in it.
Then extend the sides of the head until they meet. Then mirror the
drawing around that point. Then I can directly measure with the cad
program the two different radii of the sides of the groove. Am I
correct?
Thanks,
Eric


You want to make the o-ring groove circular in cross section?
Grooves are usually rectangular to allow the o-ring to squish in
compression.

I think he's trying to translate the theoretically conical circular
relief below the outer cutting edge into a cylindrical relief he can
more easily grind.

-jsw

I haven't tried very hard to follow all of this, but is he talking
about grinding a circular or conical side relief on the tool? Because
face-grooving tools typically are ground with a straight relief all
around.

Unless he really can exploit some extremely small advantage by making
the reliefs as compliant to the grooved shape as possible, there
doesn't seem to be much of an advantage to making it so complicated.

Or maybe I'm missing the point -- no pun intended.

--
Ed Huntress