X-axis lead screw replacement

Now that I'm more or less caught up on home fix-its since retirement, I've been re-assembling a Hardinge TM mill. I bought this thing from
Dick Triemstra 5 years ago or so. It was partially disassembled when I got it. Upon further disassembly for cleaning, it became apparent that it had led a very neglected life. Everywhere there should have been oil, there appeared to be a paste made mostly of dirt, with some grease. Wear on the ways was significant.
Anyway, I cleaned the parts up, stripping the repaint job, which appeared to be grey house paint applied with an old, much used warehouse broom right over the old dirt, grease, and spooge. I found I don't much care for painting, and there it sat until recently. Now I've finished painting it with grey epoxy (to nowhere near Hardinge standards) and started the reassembly. So far, the knee, saddle, and table are back on, with other minor bits. Once cleaned up and oiled, it's apparent Hardinge built to a high standard. There is very little lash in the Y and Z axes once I adjusted the nuts. Wear on those two screws isn't that bad, although the ways are another story.
So now to the x-axis lead screw. It's about 31" long overall, with 16" of 5/8" x 10 tpi acme thread, about a foot of 5/8" shaft through the handle end, and a short 1/2" dia. section at the end opposite the handle. In addition, there's about 14" of keyway through the threaded section for the original power feed. I'm thinking I'll order some precision screw and round nuts from McMaster along with some shafting, then assemble the sections with bores, spigots, and silver solder. I can use the mill with the old screw to cut the keyway, although it's doubtful I can do it in one setup.
McMaster has 1018 and 4140 materials available. I'm thinking 1018 for ease of machining for my limited hobby use. Does this sound like the best choice, and does anyone have other input for me? Thanks.
Pete Keillor
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On Thu, 25 Jun 2009 14:00:57 -0400, Pete Keillor

I used a length of 4140 1/2-10 from McMaster recently (p/n 98940A625) and it machined easily with a much better finish than I'd expect from 1018. I assume you'll cut the keyway with a milling cutter, not an endmill, so I wouldn't be concerned about using the 4140.
You probably want to avoid machining in the vicinity of the joints after they're brazed in the unlikely event they cool quickly enough to increase the hardness of the 4140. Or experiment with a piece scrap first to see how it behaves.
BTW, the backlash between the screw and nut was very low and the accuracy better than the advertised .009"/foot.
--
Ned Simmons

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wrote:

Thanks, Ned. Yes, I'll get a cutter. Did you use HSS to machine yours?
Pete
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On Thu, 25 Jun 2009 17:27:26 -0400, Pete Keillor

I think so, at least for the turning. Probably carbide for the milling, but I always use carbide endmills if I have a choice. The hardness on the 4140 screws is 271 Brinell ~ Rc28, which is not a problem for HSS.
--
Ned Simmons

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