On Jul 18, 12:23*pm, Ignoramus25765 ignoramus25...@NOSPAM.
25765.invalid wrote:
On 2011-07-18, Ed Huntress wrote:
...
Ed, keep in mind that they are tapered pipe taps. They are not
straight. "True size" does not make as much sense for a tapered tap,
if you think about it.
...
i-

Perhaps not, but uneven metal removal will make some flutes cut deeper
than others.

I got an acceptably sharp edge by grinding the (formerly) curved
relief between centers on my surface grinder, with a spring finger
locating the gullet side of the edge. Grinding either the taper or the
gullet doesn't affect the thread diameter on a straight tap since it
only moves the tapered cutting surface a short ways into the full-form
threads. AFAIK these don't have any back relief.

jsw