"whit3rd" wrote in message
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On Thursday, April 23, 2015 at 2:42:08 PM UTC-7, Jim Wilkins wrote:
"Jim Wilkins" wrote in message
...
"Jim Wilkins" wrote in message
...
wrote in message

I think I see how to do this now.

Draw the cross-section, extend the bottom of the groove to the
centerline and use the distance from the centerline intersection
to
the OD of the groove bottom as your hole radius, to figure the
outer
edge circular relief. The inner edge relief can be flat since the
groove curves away from it.
-jsw

That was ambiguous. Extend the line that defines the bottom end of
the
groove inward to the centerline. It will be parallel to the angle
of
the screw head.

The operation you describe will not, however, generate the conic
section (which
is an ellipse) which is perpendicular to the cutter's travel
direction. Ideally,
oughtn't the radius be matched to the osculating circle of that
ellipse at
the point of cut? I think what is called for, is the Riemannian
curvature
of the cone (of whatever angle, at whatever radius) which is the
workpiece.

Gee, I still sound like a math major, and it has been some years...

I was stuck on how to fixture and grind the osculating circle, but all
it takes is a slightly tighter radius on an offset center for
clearance, assuming the tool doesn't have to hold exact shape when
reground.
-jsw