PDA

View Full Version : DIY metal spinning lathe; re spindle bearings



Lee in Texas
08-07-2007, 01:44 PM
Can bronze bushings take the extra hp and rpm of a metal spinning lathe? I'd like to make one and I was thinking of starting with old lathe parts. It would be great to have a ready-made spindle rather than making a custom one.

platypus2020
08-07-2007, 02:29 PM
Lee,

Just talked to my friend that rebuilds to antique auto headlights, who spins on a almost daily basis, 2 of the 3 spinning lathes he has from the 40's, have bronze bushings as spindle bearings. He said that with these lathes, the spindle speeds are not that high, you have to keep the speeds low because the brass will work harden if spun too fast, and motor hp is in the 2-3 hp range. These machines will spin up to 20" diameter (starting size).

jack

Lee in Texas
08-07-2007, 02:45 PM
Awesome. :D

stuntrunt
08-07-2007, 03:25 PM
I learned metalspinning from someone who'd been doing just that for nearly 50years. He says to prefer bronze bushes to rollerbearings and he very much dislikes ballbearings. Roller- or ballbearings don't give as nice a finish as do bronze bushings, or so he says... They also last a lot longer.
I have to say that personally I dont not have enough experience to notice any difference, but since he spent the last 50 odd years strapped to a lathe with an enormous leather belt...
Even at 72 he'd still do three or four sets of steel rims for oldtimers and a few silver vases and a batch of aluminium lampshades in a day's work.
I usually tend to believe what he has to say.

toastydeath
08-07-2007, 03:55 PM
Roller bearings tend to brinell the surface of the bearing race under heavy loads, and are definitely more mechanically noisy than a plain bearing.

Alistair Hosie
08-07-2007, 06:01 PM
It amazes me he could tell what kind of bearings were in the headstock from just using the lathe.Absolutely amazing .Alistair

DR
08-07-2007, 06:21 PM
Can bronze bushings take the extra hp and rpm of a metal spinning lathe? I'd like to make one and I was thinking of starting with old lathe parts. It would be great to have a ready-made spindle rather than making a custom one.

Whether they'll do the job will depend on their size, etc.

I see the old Craftsman wood lathes all the time with bronze spindle bearing, the spindle always have way too much play due to wear of the bearings.

On the other hand if you find a lathe headstock from an older, very heavy duty lathe it would do the job. Realistically, it isn't likely you'll find one of the heavy duty plain bearing headstocks though.

BTW, a properly designed and manufactured ball or roller bearing headstock will be just fine. If they weren't the best design for a headstock would CNC lathes use them?

Lee in Texas
08-07-2007, 10:22 PM
Whether they'll do the job will depend on their size, etc.

I see the old Craftsman wood lathes all the time with bronze spindle bearing, the spindle always have way too much play due to wear of the bearings.

On the other hand if you find a lathe headstock from an older, very heavy duty lathe it would do the job. Realistically, it isn't likely you'll find one of the heavy duty plain bearing headstocks though.

That's good information to have. Is there any reason why new bearings couldn't be made from bronze stock?


BTW, a properly designed and manufactured ball or roller bearing headstock will be just fine. If they weren't the best design for a headstock would CNC lathes use them?

Heck if I know. I'm likely the greenest HSMer on this board.

lazlo
08-07-2007, 10:51 PM
BTW, a properly designed and manufactured ball or roller bearing headstock will be just fine. If they weren't the best design for a headstock would CNC lathes use them?

Agree with DR -- the finest toolroom lathes ever made use(d) ball bearing headstocks...

DR also has a good point about wood lathes for metal spinning: there's a free video short floating around that was distributed by the guy selling the "Introduction To Spinning" DVD. I think he's the guy who hosts the Spinning Yahoo Group.

In any event, he mentioned in his free video that wood lathes were great for metal spinning.

Also, you might be interested: the show "How It's Made" on the Science Channel has a neat segment on modern metal spinning in the "Aluminum Pots" episode. They show a CNC spinning lathe -- it uses what looks like a roller blade wheel instead of the spoon-like tool that manual spinners uses. They also have a section showing a guy hand-spinning light fixtures on an old manual lathe. It's amazing how fast he can churn-out fixtures.

By the way Lee, sorry I missed you a couple of weekends ago -- my Wife is 8 months pregnant, and my Mother In Law was in town for a looonnnnggg weekend. My Mom is coming to pick up our 4 year-old daughter tommorrow so my Wife and I can have 3 weeks of peace and quiet before the new baby is born, so I'm planning to spend a lot of time in the shop -- it would be a great time for you to stop by, if you're still interested...

toastydeath
08-07-2007, 10:55 PM
Just a note, a plain bearing is not a bushing.

A plain bearing (headstock of an old lathe) requires active lubrication of a specific viscosity, and has a specific spacing between the sliding members so that the bearing can ride up on the oil film and not touch. A bushing, by comparison, does have physical contact between the two members.


BTW, a properly designed and manufactured ball or roller bearing headstock will be just fine. If they weren't the best design for a headstock would CNC lathes use them?

Any bearing is a compromise.

CNC lathes do not take the heavy loads older lathes did. Even the grades of carbide used a CNC turning center are different than the ones found in 15-50 horsepower lathes of old. A roller bearing spindle has to be much, much larger to handle the same load of a much smaller plain bearing spindle. Even then, the roller bearing will be susceptible to brinelling and will wear under heavy or interrupted use much faster than a plain bearing will. Roller bearings are physically noisy, no matter how well manufactured they are. The have a larger overall asynchronous error than plain and hydrostatic bearings do.

That being said, roller bearings have no static friction, and a very low dynamic friction. They can be fairly accurate, handle high speeds, for a relatively low cost. Which is what CNC turning centers are looking for.

Plain bearings tend to be very mechanically quiet, handle higher loads per size, and be more accurate from an asynchronous error standpoint. They have high static stiffness. They also have high static friction, and are very much limited in RPM capacity, as the fluid flow of the bearing will produce dry spots and rubbing as temperature and speed increase.

Most very large machine tools use plain bearings, because there's so much weight, and the speed is relatively low. That being said, there are large machine tools (mostly roll lathes) that use truly massive (larger than the chuck) sets roller bearings. It all depends on what the designer's priority is. On CNC or high speed equipment, a roller bearing is usually the way to go.

Lee in Texas
08-07-2007, 11:11 PM
Agree with DR -- the finest toolroom lathes ever made use(d) ball bearing headstocks...

DR also has a good point about wood lathes for metal spinning: there's a free video short floating around that was distributed by the guy selling the "Introduction To Spinning" DVD. I think he's the guy who hosts the Spinning Yahoo Group.

In any event, he mentioned in his free video that wood lathes were great for metal spinning.

Also, you might be interested: the show "How It's Made" on the Science Channel has a neat segment on modern metal spinning in the "Aluminum Pots" episode. They show a CNC spinning lathe -- it uses what looks like a roller blade wheel instead of the spoon-like tool that manual spinners uses. They also have a section showing a guy hand-spinning light fixtures on an old manual lathe. It's amazing how fast he can churn-out fixtures.

By the way Lee, sorry I missed you a couple of weekends ago -- my Wife is 8 months pregnant, and my Mother In Law was in town for a looonnnnggg weekend. My Mom is coming to pick up our 4 year-old daughter tommorrow so my Wife and I can have 3 weeks of peace and quiet before the new baby is born, so I'm planning to spend a lot of time in the shop -- it would be a great time for you to stop by, if you're still interested...


If I do find an old headstock with bronze bearings, is there any reason I couldn't just make new bearings from bearing bronze barstock? I just love the idea of using a ready-made spindle.

It would be fascinating to be able to make things from spun metal. There are a few things I want, but they're certainly not stocked by anyone. For less than a custom order, I could make a spinning lathe.

It would be great to visit, but I don't think I can get to Austin until the time your baby is due. I'm working security for a party this weekend. Next weekend is duty for National Guard. The weekend after that I'm free...unless another security job comes up. hard to turn down 300-400 bucks for a few hours of work on a Saturday. I really can't commit to anything until the middle of October.

toastydeath
08-07-2007, 11:19 PM
You could make a new set of bearings, but you'd have to scrape the bearing by hand to develop the proper clearance and surface for oil retention. You can't just machine a new plain bearing and have it work without a very accurate lathe. The bearings in the headstock of old lathes are not bushings, and don't act the same way.

Instead, try to find an older lathe where the headstock can separate in some way from the bed, so you can use the entire unit as it comes.

lazlo
08-07-2007, 11:42 PM
If I do find an old headstock with bronze bearings, is there any reason I couldn't just make new bearings from bearing bronze barstock?.

Spinning doesn't look like a particularly precise operation. You can probably use a good, used wood lathe without mucking with the bearings...

lazlo
08-07-2007, 11:46 PM
Spinning doesn't look like a particularly precise operation. You can probably use a good, used wood lathe without mucking with the bearings...

Lee, here's the Yahoo MetalSpinning Group:
http://finance.groups.yahoo.com/group/metalspinning/

The group picture shows a wood lathe set up for metal spinning:

http://f9g.yahoofs.com/groups/g_11210586/.HomePage/__sr_/3ab3.jpg?grAq6uGB9gQiBHzP

You might ask over there for a couple of recommendations for a good, inexpensive wood lathe...

Cheers,

Robert

DR
08-08-2007, 12:18 AM
Lee, here's the Yahoo MetalSpinning Group:
http://finance.groups.yahoo.com/group/metalspinning/

The group picture shows a wood lathe set up for metal spinning:

http://f9g.yahoofs.com/groups/g_11210586/.HomePage/__sr_/3ab3.jpg?grAq6uGB9gQiBHzP

You might ask over there for a couple of recommendations for a good, inexpensive wood lathe...

Cheers,

Robert

The pictured is actually of a spinning lathe, although you can just as well turn wood on it.

The clue that it's specifically designed for spinning is the quick acting tailstock.

Look closely and you can see it has a babbit or bronze bearing headstock.

DR
08-08-2007, 12:20 AM
If I do find an old headstock with bronze bearings, is there any reason I couldn't just make new bearings from bearing bronze barstock? I just love the idea of using a ready-made spindle.

.............


If you have a lathe to make new bronze bearings why not use that lathe for spinning?

lazlo
08-08-2007, 12:25 AM
The pictured is actually of a spinning lathe, although you can just as well turn wood on it.

The clue that it's specifically designed for spinning is the quick acting tailstock.

Ah, that's interesting DR -- thanks! I didn't know you could buy purpose-built spinning lathes anymore.

DR
08-08-2007, 12:41 AM
Ah, that's interesting DR -- thanks! I didn't know you could buy purpose-built spinning lathes anymore.

Based on the headstock I don't think that's a recent model.