On Jun 26, 1:10*pm, "Ed Huntress" wrote:


It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads known
as "******* threads." The 29-degree angle, says Colvin, probably was chosen
because Brown & Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

--
Ed Huntress

I think Colvin is wrong in this case. My understanding is that the 29
degree angle is the strongest angle. It is also the angle used for
gears (14.5 degree pressure angle. ). Brown and Sharpe came out
with involute gear cutters in 1858 so they are likely the source of
the angle. Brown and Sharpe probably published a method for laying
out tools with 29 degree angles as that would be what is needed to cut
a rack using a shaper to work with 14.5 PA gears.

This is just based on bits dredged up from memory and some guessing so
please correct me if I am wrong.

Dan