"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
Tim Wescott fired this volley in
:

You beat me to it. With nearly 3/4 of an inch of hole to play with,
you
should be able to make a nice stout boring bar and use an insert for
the
sharp part.


Yeah... I'm going to have to run the trig on the point. Obviously, since
it's cutting a little on the lagging bottom shoulder and a little on the
leading top shoulder, then unlike a regular 60-degree point, it's going
to have to be a smaller angle.

And that may very well be why my tap isn't giving a decent cut, yet.



A modified tap is NEVER going to give you a decent cut unless you completely
grind away all but one flute, then grind all but one tooth off of the
remaining flute, and THEN grind a portion of the upper face of the single
remaining tooth away in a manner that provides a proper primary clearance
angle on BOTH sides of the resultant 'vee' tooth form.