Lead Screw Repair

[RickBarb]

I have a 6"x18" Atlas Lathe with a lead screw that is badly worn for about 6" near the headstock. I checked with Clausing and they want nearly $150 for a new one. I have checked ebay and they are available for considerably less, but used and I do not want to buy one with the same wear pattern as mine. What do the listees think of my chances to resurrect the existing screw by cutting out the worn portion and moving it to the end where it is seldom used. I propose to turn sockets and spigots to rejoin the pieces using loctite. Am I crazy or might it work? Opinions please. Thanks in advance. Rick

[sjames]

I don't know if your leadscew is hardened or not, but if it is, that could present a real problem for your plan.

I don't know anything about atlas lathes, is there a separate feedscrew? I'm guessing the leadscrew pulls double duty on that lathe.

what problem are you trying to resolve by fixing the leadscrew? If the screw is that worn, the ways probably are too, which would have a greater effect on your lathes accuracy. only think the lead screw being worn would effect would be threading I would think.

so to me it sounds like a pretty big project for very little gain.

but, i could be totally wrong.

[Patio]

Have you tried Fastenal yet?
I do know that Acme screw rod comes in different grades also.
My brother was thinking about getting some, and that is where he found it.
I will need some for the rotary table I am trying to bring back to life.
Just a thought.

[RickBarb]

The lead screw is not hardened. It is a small lathe and the lead screw does not pull double duty. It is only used to move the carriage. The cross slide is hand fed only. The ways do not appear to be worn very badly. I have had the lathe since 1975 when it was new except for a 12 year period that my son-in-law was using it. I suspect he used the carriage in the power feed mode a lot. The half nuts are Zamak (pot metal). They work on the unworn part of the leads crew, but not on the worn part. I am replacing them with new ones as they are badly worn. I have checked quite a few suppliers on the internet including Fastenal and none of them list a 1/2" x 16 Acme Thread. I am still in the thinking stage and not ready to take a hacksaw to it just yet. Thanks for the input. Rick

[sjames]

The lead screw is not hardened. It is a small lathe and the lead screw does not pull double duty. It is only used to move the carriage.

sorry, i meant double duty in a different way, the lathes i'm familiar with have a separate feed screw for moving the carriage, the lead screw is only used for threading. so double duty in moving the carriage during turning and threading operations.

1/2 16 seems to be an oddball, or at least not popular anymore. i don't readily see it in the places i normally look for such things.

its a pretty short length, i wonder if someone would volunteer to just make you a new one if you could provide a drawing.

I noticed in another thread folks were looking for an excuse to use their follow rest, sounds like a perfect opportunity.

[Patio]

Another option you might try is.
A guy on Ebay sells acme rods for various different lathes. Some are for the cross feed, some are for the compound. I believe he makes them, as he sells them as new. You might try him and see if he will make what you need and for how much.
If you can't find him, let me know, I will look it up and post a link here. Look under Southbend, as I know he sells those.

[refinery mike]

Hey ENCO just started carrying lead screw in their catalogue. never tried it but you may get lucky with them. They got a bunch of sizes. they also sell acme thread but i do not think that is what you want. they are just screws so you will have to turn it down at appropriate spots

[refinery mike]

I am pretty sure that the lead screw on an atlas lathe is not an acme but a square thread. They look a lot alike in pictures but they will not interchange. For instance 1/2 10 and 5/8 8 three foot sections in c1018 is about 20 dollars. 316 Stainless steel is about 150 dollars. 304 stainless is around 70 dollars.

[dly31]

I believe you could successfully turn the leadscrew end-for-end if you can make reasonably accurate spigot joints but you will still have to make new coupling parts and will have a badly worn leadscrew on the tailstock end. I think I would try to find someone to make a new one. It is too bad that the existing screw is unsuitable for making a new one. You may not have enough bed length to make it either; check everything carefully beforehand.

[wsippola]

I have heard of cutting the leadscrew and welding it back in so the worn side was at the tailstock. You can make it work.

I have a 7x10 that had a 1/2" x 16 leadscrew, not acme or square, just a V thread. I added a section to the bed and needed a longer leadscrew, so used 3/4 x 16 threaded rod and new halfnuts. Standard fine V threads. Used it for about 20 years now like that. I did need to hold the halfnuts closed as it did not have a detent for open and closed - added that last year.

So the point is since you're changing the halfnuts, you could make new halfnuts and use a more common stock thread, acme preferably. Probably doesn't even need to be the same diameter, assuming adequate clearance behind the apron.

Wayne

[TomB]

Just two thoughts. Since you are going to buy new half nuts why is the thread size critical? Enco has 3/8 x 16 so it seems like you could use that by turning down the mount points to just below the thread root and then sleeving up to the needed mounting size. But I also see an Enco 1/2 x 8, 2 start rod. Because you are looking for 1/2 x16 and it does not exist makes me wonder if you might be counting the turns from two starts. If you can see the ends of the thread you might be able to see the 2 starts. Alternativily, 1 turn of the crank would move the table 1/8" if it was a 1/2 x 8, 2 start but only 1/16" if was a 1/2 x 16.

Tom

[Harold_V]

Just two thoughts. Since you are going to buy new half nuts why is the thread size critical?

Altering the lead of the screw renders a quick change rather useless. That, of course, depends on the alteration. If the rate is cut in half, a setting for chasing a 10 pitch thread would yield a 20 pitch thread. I made that alteration to my lathe (by changing gears, not the screw) intentionally, so I'd have a lower feed rates from which to choose. Rarely is it a problem, but I also specialized in small work.

Harold