ACME ( was Re: leadscrew, acme screw, threaded rod, ballscrew

Lead screw is a generic term or how you are transfering power.
others are rack and pinion and there is a way to fix a chain or
timing belt at each end of a base and use that as the means of
movement.

ACME rod is a relativly square edge.

http://www.williamsform.com/Threaded_Rods/All-Thread_Acme_Rod/all-
thread_acme_rod.html

ACME thread is the stuff you see on vices and manual lathes and C
clamps.

it comes in a contractor grade. that would be used to clamp things
together. no real tolerance or quality.

then there is a commerical grade that is slighly better but has a
error over the length that makes it unsuitable for anything that
approximates precision.

there is also an archtechual ACME, this is usually the chrome plated
stuff or otherwise finished to look good. again, no machine value.

then there is the mechanical ACME we usually think about. designed
for machines and comes with some notation of accuaracy. often 0.006
inche per foot or worse. This is usually called leadscrew and may or
may not be termed ACME too.

then there is presision that is about 0.003" per foot or better.

regardless of which style you buy, it transfers power better than
angled threads. the higher precision, the more you pay and the
better the stuff.

the precision stuff will also be the straight and ground. that adds
to the efficiency in power transference (and cost).

like anything in this hobby, the presision stuff just costs $$$.

all-thread angled rod is also available in most of the above style
except leadscrew or precision. the best you'll get is ground or
rolled threads which move more smoothly, but the straightness and
tolerances are not there. no reason for it.

The cheapest ball screws are light years better than all-thread, but
the best ACME is better than cheap ball screws, but not much.

for power transfer, ball screws beat the others hands down. they are
just way too efficient.

Check out McMaster for the ACME stuff and they should have some write-
ups on the different types.

Dave