On 2009-06-27, Ed Huntress wrote:

[ ... ]

Where cutting forces or non-cutting friction is high, you can add sulfur to
oil and you get more film strength, with little influence on lubrication,
without increasing the puncture threshold. Tough cutting conditions, such as
tapping, benefit from the sulfur.

What is the best fluid to use for roll (form) tapping? High
sulfur? Mollybdimum Disulfide? Something else? I've got some stuff
which appears to be mostly powdered sulfur in an oil carrier -- looks
kind of like mustard, and about as thick. IIRC, it is called
"Sul-Flo". This is nice where high cutting forces are involved, but you
want good airflow to get the smell of burning sulfur out of your lungs. :-)

You can also add chlorine or a variety of
other chemicals to get a somewhat mysterious reduction in shear strength at
the cutting edge. Somehow they get right into the shear area and reduce
cutting forces. This was the subject of a lot of research during the '50s.
Maybe they have it figured out now. They didn't when I was writing about it,
in the '70s and early '80s. The extreme example of this was carbon
tetrachloride, which produced a very large reduction in shear strength right
at the cutting edge. Don't use it.

Wasn't that what was in the original Tap-Magic? Or was it
1,1,1, Trichlor? Whatever was there, it was certainly bad news when
tapping aluminum. :-)

Enjoy,
DoN.

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