On 2013-07-14, Ned Simmons wrote:
On Sun, 14 Jul 2013 11:11:46 -0500, "Terry Coombs"
wrote:
As I said , this tap cuts an oversize thread , it
measures 10.11 MM . Allowing for truncated thread profiles , the tap should
measure just UNDER 10MM , not over .

The OD of normal taps is always larger than the nominal thread size.
Look at the thread tables in Machinery's Handbook and you'll see that
the major diameter of internal threads is the nominal diameter with a
plus tolerance.

And what you want to do to check the diameter of threads is to
measure the *pitch* diameter -- which is usually done on male threads
with three wires of selected diameter down in the Vs -- two on one side
and one on the other. This measures the surfaces which should mate.

The drawing below should be viewed with a fixed pitch font like
Courier. Any of the variable pitch fonts will cause the later
(right-most) parts to fall out of alignment on your screen.

~~~~~~~~~~
| | -- micrometer anvil
|________|
/\ /\()/\()/\ /\ /\ /\ /\
/ \/ \/ \/ \/ \/ \/ \/ \



/\ /\ /\ /\ /\ /\ /\ /\
/ \/ \/()\/ \/ \/ \/ \/ \
_________
| |
| | -- Micrometer spindle
| |
~~~~~~~

The above shows how the wires should be placed, but they should be a
little bigger than shown (limits of ASCII graphics), so they project
above the thread crests. Then your micrometer can give you a precise
reading which can be converted to the pitch diameter by subtraction of a
constant which you look up.

10.11 mm OD for an M10x1 tap sounds about right.

Yes -- this makes a sharp V crest to the internal threads, to
clear any reasonable shape of crest on the mating threads -- Sharp,
flat-crested, or rounded.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---