"Tim Wescott" wrote in message
...
snip--
Do you know what the functional differences are between acme and
60-degree "regular" threads? I assume it's because regular threads tend
to wedge in when they get tight which is a good thing in a fastener and
a bad thing in a lead screw -- but I don't know.

--

Tim Wescott

Acme is used in place of a square thread to avoid wedging, but not so for
the typical 60 degree thread. Acme is used for two good reasons. One of
which is it's typically fast lead, the other is its greater strength,
particularly on small diameter parts, where a fast lead with a coarse 60
degree thread isn't possible. You do have the option of multiple entry
threads in that situation, but the Acme is still the stronger, and generally
more desirable design.

Harold