Replacing old ND bearings

Hi,

First post, but I've been lurking for a while for advice.

I have a Pratt and Whitney 3c lathe that needs the carriage bearings replaced. They're marked 077039a, and I can find a couple places to buy them online, but they're pretty extensive for only one or two.

I measured them and got 0.372" ID, 1.026" OD, and 0.356" thick. The ID is just a little too big to be a 629 metric bearing, and the OD is too small to be a 1614 bearing from somewhere like AST.

Any ideas for a new set of bearings or should I spring for the real deal? I'd prefer to get sealed instead of shielded to prevent grit from getting in there again.

Thanks

Sam

Good luck. Finding replacements for New Departure bearings is a challenge.

Any possibility of using more common off the shelf bearings with adapter sleeves/seats?

MauledByBears said:

Hi,

First post, but I've been lurking for a while for advice.

I have a Pratt and Whitney 3c lathe that needs the carriage bearings replaced. They're marked 077039a, and I can find a couple places to buy them online, but they're pretty extensive for only one or two.

I measured them and got 0.372" ID, 1.026" OD, and 0.356" thick. The ID is just a little too big to be a 629 metric bearing, and the OD is too small to be a 1614 bearing from somewhere like AST.

Any ideas for a new set of bearings or should I spring for the real deal? I'd prefer to get sealed instead of shielded to prevent grit from getting in there again.

Thanks

Sam

Click to expand...

If you are talking about carriage anti-lift bearings - the sort that run against the ground underside of a ledge on the bed, then neither ID nor OD are critical.

You can go for a match to the mounting shaft, alter it or fab new only if you must, but probably better to NOT bush it.

The clearance should be adjustable anyway, so the OD doesn't matter all that much.

If you mean a bearing INSIDE the apron OF the carriage, we need to start over with more information.

Monarchist said:

If you are talking about carriage anti-lift bearings - the sort that run against the ground underside of a ledge on the bed, then neither ID nor OD are critical.

You can go for a match to the mounting shaft, alter it or fab new only if you must, but probably better to NOT bush it.

The clearance should be adjustable anyway, so the OD doesn't matter all that much.

If you mean a bearing INSIDE the apron OF the carriage, we need to start over with more information.

Click to expand...

Thanks! These bearings hold the end of the screw that isn't in the nut. They're located inside the slides. The cross slide has one and the topside/compound has two, one on either end of the screw.

From what I can tell, they're​ sort of clamped at either end by a back nut and the nut that attaches to the knobs, so they're only there to keep the screw straight and the dimensions aren't super critical.

I'm going to keep trying to work all the brass out of the bearings and maybe repack them. Why shouldn't I bush it?

Thanks

Sam

MauledByBears said:

Thanks! These bearings hold the end of the screw that isn't in the nut. They're located inside the slides. The cross slide has one and the topside/compound has two, one on either end of the screw.

From what I can tell, they're​ sort of clamped at either end by a back nut and the nut that attaches to the knobs, so they're only there to keep the screw straight and the dimensions aren't super critical.

I'm going to keep trying to work all the brass out of the bearings and maybe repack them. Why shouldn't I bush it?

Thanks

Sam

Click to expand...

Then you are not talking about 'carriage bearings' at all.

Cross slide and compound rest actuating screws, rather. Those have some leeway also as to ID, OD, and even face width.

That said, they still have to do their job, so a good fit-up is necessary, hopefully without altering their mounts nor the screw itself.

If the old ones have had tramp metal in them? They'll never be new again, but rotation speeds are so low they might still be smooth enough to work OK. It is not the spindle's bearings you are dealing with here.

Worth a try cleaning them up. Otherwise, "bush away!" Just do it well.

For such a low speed operation I have to wonder if a bronze bushing would be good enough, maybe with a thrust washer. With ND bearing I assume this is at least 50 years old. At that age I doubt it will be used 24/7 for war production. So I think a ballbearing may be overkill for the rest of it's useful life. If the bushing only lasts 25 years of low usage would that be enough for your lifetime?
Bill D

Oh yeah, this thing is old. From what I could look up, they stopped making these lathes in 1947.

That said, whoever owned it took really good care of it, and I don't think it was used a whole lot. You can still see the scrape marks on the ways in some places.

The bearings got some brass in them from the cabinet maker that owned it before me. A lot of the T-slots were also full of woodchips, brass, and what looks like dried up grease or wax. Nothing a little mineral spirits can't handle, and the bearings are considerably less chewy after I gave them a good soak and a few taps to get the chips out.

I'm going to run these as long as I can. I don't think they're a critical part since they weren't even pressed onto the shaft. They're a close fit, but they just slide on and are retained by nuts and the handles.

If these bearings fail or get chewy again, I'll probably try to bore ~0.020" out of some 629-2RS bearings and use those. Failing that, I'll have to make some bushings.

Thanks fellas!

MauledByBears said:

Oh yeah, this thing is old. From what I could look up, they stopped making these lathes in 1947.

Click to expand...

'47? That ain't "old"! I was already two years old. Both of my 10EE are older, yet ('42 and '44). SOME PM members have lathes so old the swarf they came in with could very well test positive for Neanderthal or Denisovan Mitochondrial DNA!

Accuratebearing.com
Toll Free 800-323-6548 or 630-543-2100
Fax Toll Free 800-323-3116 or 630-543-2116
E-mail: [email protected]

Try these guys, they carry NOS bearings.

And a spritely 70 years old she is! Haha, sorry. I'm 23 so anything older than the Nixon administration is ancient history to me. They tell me stuff from the "good old days" was built to last, I bet 70's the new 45 eh?

I'm jealous, I'd never heard of the 10EE. Those are some beautiful machines, art deco and machine tools, what's not to love?

Monarchist said:

'47? That ain't "old"! I was already two years old. Both of my 10EE are older, yet ('42 and '44). SOME PM members have lathes so old the swarf they came in with could very well test positive for Neanderthal or Denisovan Mitochondrial DNA!

Click to expand...

My Warner Swaseys have been producing crude oil from the swarf....and welcome source of income...