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

Nobody is commenting on the screws mcmaster calls: "Precision
Modified-Acme Lead Screws and Nuts" Currently, these are on page 967
on-line. These really are not "Acme" screws so it is a little
misleading. They are rolled precision "Lead Screws". I was told that
Mcmasters screws come directly from Kerk. Unfortunately, McMaster only
sells the lighter duty self adjusting antibacklash nut, but do not rule
it out. If used them on Z axis applications and they will run day in and
day out for a year maybe two all the while maintaining no backlash. I
have also ordered the Screws from Mcmaster, (its cheaper) and then
ordered Kerks VHD nuts.

So instead of this .006-.009" per foot slop you have to wrestle out
using conventional Acme screws, these offer .0006 per inch.

I consider this style leadscrew the only option short of ball screws and
in some, no, - many - cases much better than using ball screws.

Of course they are priced somewhere between the cheap stuff and the
expensive stuff.....

Chris L


turbulatordude wrote:

>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
>
>
>
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