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Login to post Forums » Off-topic discussion » Anyone here replaced the lead screw on a lathe?

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Feb. 13, 2012 11:14 a.m. ditchdigger Dork

I have an old Clausing-Atlas 4900 series 10" lathe. I saved it from a scrap metal run for $50 about 5 years ago.

Looks just like this

Due to the fact that I have it wired for 110V it has very little torque so I don't use it very much and instead I save all my projects for the 15" lathe at work. That seems silly since I have this sucker in my garage.

I am in process of converting it to a 3hp DC motor with variable speed control so I don't have to mess with belt changes any more. While cleaning it up and checking it out I notice that the cross slide lead screw has almost 1 full turn of slop to it. I need to fix that right away.

Anyway. Is it usually the lead screw or the captive acme nut that wears first? I am trying to save a few bucks and buying both will be over $200. The nut is about $75 from Clausing.

Can I use standard fastener store acme thread and nuts and machine them to fit? Will they be accurate enough?

I have used mills and lathes daily for well over a decade but this is my first dalliance into repairing them.
Feb. 13, 2012 11:31 a.m. Giant Purple Snorklewacker SuperDork

I have a grizzly that I disassembled to clean and adjust. It seems reasonable that you could adapt a screw part from any lathe to any other if they are significantly cheaper - but the carriage nut and half nut parts would need to be replaced and I was surprised that on mine - they were somewhat more complicated a shape than just a captive nut with a nylox screw in them. I would not be able to fabricate one to a different thread spec with my machine skills.
Feb. 13, 2012 11:58 a.m. RealMiniDriver SuperDork

I've never played with a lathe, but I work with centerless grinders. If a lead screw is anything like a ball screw, I might be able to help you out. What length, diameter, etc. is your lead screw? Picture?
Feb. 13, 2012 12:01 p.m. ditchdigger Dork

I will pull it apart tonight and measure it. I know it is acme but that is about all I remember.
Feb. 13, 2012 2:44 p.m. Hal Dork

I would save the money and buy the factory parts. You might be able to cobble something together that would drive the cross slide but if the thread pitch is not an exact match your thread cutting ability would be "screwed" (pun intended).
Feb. 13, 2012 8:16 p.m. ditchdigger Dork

Surprise, surprise! I was wrong. It isn't acme thread. Looks to be 1/2-11? and left hand thread. Not standard stuff.

This looks to be the culprit

If there was a tap available out there I would be able to make this with no problem. I will look into this a bit more.

In other GREAT news. Look what I scored today.

one fuly functional 2 axis DRO. This lathe is gonna be a badass lil' mofo when done.
Feb. 13, 2012 8:29 p.m. Giant Purple Snorklewacker SuperDork

That is super easy to make if you already own a tap in that size. Otherwise - I suppose you could make it, drill it and go to a shop with a six pack and ask someone to thread it for you.
Feb. 13, 2012 10:34 p.m. ditchdigger Dork

After spending more time with the calipers it is indeed 1/2-10 LH acme thread. Just very worn. I don't have the tooling to cut acme. Calling clausing in the morning.
Feb. 13, 2012 10:42 p.m. Taiden SuperDork

turn one on your lathe?
Feb. 14, 2012 3:08 a.m. novaderrik SuperDork

we've got 1/2-10 LH ACME taps here at work.. too bad you're way out on the left coast..
Feb. 14, 2012 10:06 a.m. ditchdigger Dork

The kind of statement you never want to hear.

"Thank you. We will contact the engineering department and get a quote on how much it will cost to make you one"

I suppose it was overly optimistic to assume they had parts for a 40+ year old lathe on the shelf.

Working on an alternate plan.
Feb. 14, 2012 10:12 a.m. Taiden SuperDork

Mcmaster Carr
Feb. 14, 2012 10:16 a.m. alfadriver SuperDork

In reply to ditchdigger:

If novaderrik has the tap, wouldn't it make sense that someone near you would as well?

And if so, wouldn't it be possible to weld in a sleve, and then tap it? While it takes some work to weld cast iron, it's very possible, and machining isn't that hard for the pros.

Seems as if you should be able to have that part restored locally....

(and I'm enjoying this thread!)
Feb. 14, 2012 10:20 a.m. DILYSI Dave SuperDork

I grew up on that exact same lathe. It also had a ton of slop in the screws. It would still make very accurate parts. I wouldn't bother replacing it.
Feb. 14, 2012 10:33 a.m. DILYSI Dave SuperDork

If that's not an acceptable answer, McMaster P/N's 1343K234 and 99030A405 should get you started on fabbing replacement stuff for not too much money.
Feb. 15, 2012 7:17 p.m. ditchdigger Dork

Oddly enough those two part numbers were already whisking their way to me by the time you posted them.

What came this morning

Oh yeah.....This is totally gonna work!

So that bronze bit was way too big.

Turned it to 5/8" then bored out the worn threads to that size

Press fit and then a bit of solder to ensure they won't decide to seperate

On to the screw. I cut a piece an inch longer than what I needed to replace and duplicated the old one

Look at how worn the threads are!

cut the shaft off and bored it 3/8"

Then using the dead center and chuck in the lathe to ensure they were as straight as possible I soldered them together.

All reassembled!

I slapped it back together and hot diggity! If there is any slop I cannot measure it. From 0.0987 to as near as I can tell 0.0001 for under $50. I am quite happy.
Feb. 15, 2012 11:10 p.m. motomoron Dork

That's the exact, perfect repair.

Part of the joy of owning old iron is making the stuff to keep it running. Which of course enables the purchase of more machines so you can make everything to keep all the machines running.

(Says the guy who just finished unloading a 600 pound, 12 drawer Vidmar cabinet alone w/ an engine hoist and pallet jack, cause there's 2 pallets of tooling and cutters that needs to go somewhere)
Feb. 15, 2012 11:46 p.m. DILYSI Dave SuperDork

Nice!
Feb. 16, 2012 1:29 a.m. Derick Freese Dork

This is one of the coolest things I've seen in a while, and I fix stuff with similar methods all the time.
Feb. 16, 2012 1:52 a.m. 4cylndrfury SuperDork

Thats an awesome post, thanks for sharing it! Theres a pretty decent machining section of a metal casting forum I visit HERE... if you visit, youll need to use the drop downs at the bottom to expand the date range of threads to display (stupid issue from switching forum software is this odd limited date range thing). Theres several good machine restos in there, and not just lathes either

diy cnc router
rebuilding a rotary table
Feb. 16, 2012 6:55 a.m. alfadriver SuperDork

That is VERY cool. Nice job!
Feb. 16, 2012 7:45 a.m. Taiden SuperDork

Sweet!
Feb. 16, 2012 9:09 a.m. ditchdigger Dork

I am very pleased. So much so that I might just try and move the 1000 pound thing out, give it a good cleaning and try and install the DRO this weekend.
Feb. 16, 2012 11:57 a.m. Taiden SuperDork

Let me ask you this,

how many times did you sit there moving the carriage handwheel back and forth feeling the lack of play with a huge grin on your face?
Feb. 16, 2012 12:08 p.m. ditchdigger Dork

oh not much. 40-50 times is all

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