(acme) screw hardness?

While cleaning my new-to-me lathe (older 1950's 12.5x36 cincinnati) up, I discovered the crossfeed had quite a bit of backlash in it due to a worn out
screw and also the (brass?) nut that it goes through. I've entertained the idea of making a new one (seems like a nice project once I get everything up and running). But, how hard are these usually? Since that part is already back together, it's a bit late to do the file test to it. Also, what would one make this out of (granted, it depends on how hard it needs to be), but I'm thinking something along the lines of drill rod should work right? And one last question; Whats the best material to make the "nut" that this acme screw goes through? Not being great at metaluragy about all I could come up with is some sort of brass.
Thanks for the advice fellers (and ladies).
-- Lynn "I have opposable thumbs, and I'm not scared to use em" Amick http://www.amickracing.com
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Typically the nuts are bronze. I replaced some of the nuts in my Atlas lathe with Aluminum Bronze stock from McMaster-Carr. Left and right hand Acme taps in most popular sizes are available, and I replaced some of my screws (cross slide, compound, and tailstock) with precision acme ground rod, also from McMaster. Works great, and the lathe is now nice and tight. Well, a little slop still in the compound dovetails...
Al

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On Sun, 2 Nov 2003 18:49:15 -0800, "Lynn Amick"

To see 20 to 30 thou of slack when reversing the crossfeed on new machines is not uncommon.
Some of the backlash can be adjusted out at where the crossfeed knob is attached to the slide. To figure out how much wear is really on the fixed nut that is on the saddle, go all the way to the end of the screw and push and pull the cross slide by the tool post with a D.I. set up to read the travel. Then go to the center or most worn spot and do that again and you'll get an idea of how much wear is there.
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wrote: ------- An easy fix is to buy a length of rolled acme threaded rod and put a turned down shaft on one end and cut off the acme thread on the cross feed shaft and bore a hole for a press fit of the new acme shaft. Since you are using rolled acme threaded rod it will probably have a hardness of around 42 rc which is adequate for hobby lathes. A bronze nut can be purchased from the same source at less than cost of an acme tap. Don Warner ---------

out
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Boy, all this buying stuff sure takes the fun out of it (but likely takes the frustration out too lol). As for how much backlash I have, add another 0 behind the 20-30 thousandths and you'd be in the ballpark. Infact the screw almost looks like a v groove (and point on the tip of the threads), how this got so worn out, yet the rest of the lathe is in such good shape, who knows.
Thanks for the advice guy! I think I will end up buying what I need and slightly adapting it to do it's job, but if I run out of projects, I might still tackle building one.
-- Lynn "I have opposable thumbs, and I'm not scared to use em" Amick http://www.amickracing.com
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