Replace babbitt split bearings in old wood lathe headstock

[Overland]

Interesting project. Customer wants to replace bearings. Headstock too small to use pillow blocks, and bearing diameters are in necked down part of spindle. He's not concerned with overall shape of the bearings, just needs functionality.
Best idea I have is:
- start with a piece of rectangular section bronze, say 3" x 1.5".
- bolt 2 pieces together to form a square
- turn square section to round, avoiding bolts
- now I've got a split round blank
- turn bore to fit shaft
- mill flats on outside to fit in headstock
- possibly add shim material before bolt halves together for long term adjustment
I've not seen the job yet, just photos, so don't know how accurate headstock is for my idea to work.
I guess I could line bore the bearings in the headstock, but that wouldn't be easy with my equipment.
Another thought would be to turn the bore small, and scrape to ensure shaft fits nicely - not an easy task.
I have more pics if these are not clear to define problem.
Any other, better ideas ?
Thanks,
Bob

edit: the bolts to hold the two halves together would only be needed for machining. The holes would be left in the finished job.

 

[TGTool]

Any chance there's an automotive connecting rod or main bearing shell set that would fit the shaft?

 

[Overland]

Any chance there's an automotive connecting rod or main bearing shell set that would fit the shaft?

The ones I have seen have a width of less than 1/2 the diameter, so would need a few, and a way to mount them.

 

[MrStretch]

Wascally wabbit.

 

[99Panhard]

In period the technique was to make the bearing in two halves as you've described except they soldered the two pieces together and then machined them as if they were one piece. I have a similar problem where a very old metal lathe I have where the bearings are square. Because it's a metal lathe I was thinking of making them both in one piece and cutting them apart.

On second thought, they also had problems with the two halves coming apart occasionally before they were finished. It might be better in this case to simply make it from a piece of bronze and slit it after machining. Then you could use shims to take up the kerf of the say. When I made split camshaft bearings I did it as you initially described and it has worked well (the two times I've done it.)

 

[Joe Michaels]

Here a few thoughts:
-the spindle journals look OK
-the bearings are babbitted
-this is a wood turning lathe, not an engine lathe for turning metal, so not needing to be as precise in the bearings

With those thoughts as basis for repair ideas, why not melt out the old babbitt and re-babbitt the existing bearings ? The lathe spindle can be used as a mandrel for re-babbitting, so the bearings will be poured at very close to final size. Once the clearance is set with shims, some spotting and scraping is usually required. These are neither high speed nor really precise bearings in this application. Rebabbitting using the headstock to hold the bearing shells in position and jigging the spindle to establish it on the correct centerline is how I'd go about it. I've poured some babbitted bearings on woodworking machinery, as well as line-shaft bearings, so the idea of rebabbiting seems the easiest way to make the repairs.

As for purchasing bronze bar stock to make solid bearings, you will be up against a couple of factors weighing against it:
-price of that much bronze
-grade of bronze readily available as heavy bar stock. Typically, bearings of this sort would be made of a softer leaded bearing bronze such as a 660 grade. This is usually available as round bar. Rectangular and square bronze stock is most typically available in alloys of aluminum or manganese bronzes. These are a much harder bronze than the 660. When designing a plain bearing such as these headstock bearings, the hardness of the journals is considered in comparison to the hardness of the bearing material. Hence, for a hard bronze bearing such as a manganese or aluminum bronze, the spindle journals need to be quite hard. I suspect on this old lathe, the spindle journals are soft, likely a mild steel. Running mild steel journals in a harder bronze bearing may result in premature wear of the spindle journals.

I would be fairly sure that a very soft grade of babbitt used in the spindle bearings in that old a wood turning lathe. Try scraping some with a pocket knife blade, and if you can pare or whittle off a nice shaving easily, the bearings are a softer babbitt. This is likely a leaded babbitt metal rather than a 'high tin babbitt' which would be used on higher speed/heavier loaded bearings.

Again, this old lathe is nothing fancy or sophisticated in terms of its bearings. With a wood cone pulley on the spindle that looks to be coming apart at the glued joints, this is neither a high speed spindle, nor one for heavy loads. There are umpteen youtubes about rebabbitting or 'repouring' this type bearing. No real specialized equipment is needed other than maybe an oxyacetylene torch to melt out the old babbitt and to smoke the journals with lampblack. Dave Richards in his "steam powered machine shop' melts babbitt in a steel skillet on an electric hotplate. I've used a plumber's stove (formerly used for melting lead for 'running joints' on cast iron soil pipe), and I've used a propane 'weed burner', and I've melted babbitt with the melting pot in a charcoal fire in a forge hearth. From what I see of these bearings from the original post, I'd go with rebabbitting instead of knocking myself out reinventing the wheel and going for broke buying large chunks of bronze.

 

[Overland]

Here a few thoughts:
-the spindle journals look OK
-the bearings are babbitted
-this is a wood turning lathe, not an engine lathe for turning metal, so not needing to be as precise in the bearings

With those thoughts as basis for repair ideas, why not melt out the old babbitt and re-babbitt the existing bearings ? The lathe spindle can be used as a mandrel for re-babbitting, so the bearings will be poured at very close to final size. Once the clearance is set with shims, some spotting and scraping is usually required. These are neither high speed nor really precise bearings in this application. Rebabbitting using the headstock to hold the bearing shells in position and jigging the spindle to establish it on the correct centerline is how I'd go about it. I've poured some babbitted bearings on woodworking machinery, as well as line-shaft bearings, so the idea of rebabbiting seems the easiest way to make the repairs.

As for purchasing bronze bar stock to make solid bearings, you will be up against a couple of factors weighing against it:
-price of that much bronze
-grade of bronze readily available as heavy bar stock. Typically, bearings of this sort would be made of a softer leaded bearing bronze such as a 660 grade. This is usually available as round bar. Rectangular and square bronze stock is most typically available in alloys of aluminum or manganese bronzes. These are a much harder bronze than the 660. When designing a plain bearing such as these headstock bearings, the hardness of the journals is considered in comparison to the hardness of the bearing material. Hence, for a hard bronze bearing such as a manganese or aluminum bronze, the spindle journals need to be quite hard. I suspect on this old lathe, the spindle journals are soft, likely a mild steel. Running mild steel journals in a harder bronze bearing may result in premature wear of the spindle journals.

I would be fairly sure that a very soft grade of babbitt used in the spindle bearings in that old a wood turning lathe. Try scraping some with a pocket knife blade, and if you can pare or whittle off a nice shaving easily, the bearings are a softer babbitt. This is likely a leaded babbitt metal rather than a 'high tin babbitt' which would be used on higher speed/heavier loaded bearings.

Again, this old lathe is nothing fancy or sophisticated in terms of its bearings. With a wood cone pulley on the spindle that looks to be coming apart at the glued joints, this is neither a high speed spindle, nor one for heavy loads. There are umpteen youtubes about rebabbitting or 'repouring' this type bearing. No real specialized equipment is needed other than maybe an oxyacetylene torch to melt out the old babbitt and to smoke the journals with lampblack. Dave Richards in his "steam powered machine shop' melts babbitt in a steel skillet on an electric hotplate. I've used a plumber's stove (formerly used for melting lead for 'running joints' on cast iron soil pipe), and I've used a propane 'weed burner', and I've melted babbitt with the melting pot in a charcoal fire in a forge hearth. From what I see of these bearings from the original post, I'd go with rebabbitting instead of knocking myself out reinventing the wheel and going for broke buying large chunks of bronze.

Thanks Joe for the good analysis.
I'd have to make up a mould to recast the bearings, as there is not much to the headstock. And not sure how I'd cast two halves.
Bob

Edit: just found 3" x 1.5" x 12" long 954 bronze bar for $215 from Online metals.
Doesn't seem too expensive.

 

[plastikdreams]

Wascally wabbit.

 

[gbent]

It doesn't appear to me there is anything wrong with the existing babbit. All it appears to need is a little oil, and possibly tightened a smidge.

 

[JST]

Possibly a bit of polishing of the shaft, then some tightening up. The shaft has a little more grooving than I'd personally prefer. Might be the lighting.

 

[john.k]

The makers used babbit for a reason.........bronze bearing requires a hardened shaft ,and the oilways had better be of sound design and construction .

 

[Joe Michaels]

John.k

Thanks for concurring with me regarding journal hardness vs bearing metal hardness. As I posted, my thinking is the spindle of the old wood turning lathe was made of a mild steel. relatively soft. The babbitt used is likely a leaded soft grade of babbitt. As you correctly note, bronze bearings call for harder spindle journals. As I posted, getting hold of a softer bearing bronze for the replacement bearings in the form of large rectangular bar stock, is nigh unto impossible. What is readily available for the softer (660 grade) bearing bronze is round bar. The rectangular and square bronze bar is most usually made from manganese or aluminum bronze alloys. Much harder, and not a good choice for this lathe's bearings with the existing spindle.

The original bearings were babbitted by using the cast iron shells as the molds. With some babbitt damming compound (a kind of putty) and the use of the spindle as the mandrel, the existing bearings could be re-babbitted.

I'd clean up the existing babbitting and take a close look for damage. If there were shims between the bearing halves, possibly, removing some could give the existing bearings a new lease on life. I.E., remove shims to close up the clearance, then spot and scrape the existing babbitt to conform to the spindle journals. It might not be the most perfect or prettiest show in town, but for this application, would likely do just fine for another few decades. Sometimes, attempting to improve on a simple and very old design does not give as good a result as the original design did in service.

 

[Overland]

It doesn't appear to me there is anything wrong with the existing babbit. All it appears to need is a little oil, and possibly tightened a smidge.

I've not seen the job yet, just some photos, so you could certainly be right.
Bob

 

[Overland]

John.k

Thanks for concurring with me regarding journal hardness vs bearing metal hardness. As I posted, my thinking is the spindle of the old wood turning lathe was made of a mild steel. relatively soft. The babbitt used is likely a leaded soft grade of babbitt. As you correctly note, bronze bearings call for harder spindle journals. As I posted, getting hold of a softer bearing bronze for the replacement bearings in the form of large rectangular bar stock, is nigh unto impossible. What is readily available for the softer (660 grade) bearing bronze is round bar. The rectangular and square bronze bar is most usually made from manganese or aluminum bronze alloys. Much harder, and not a good choice for this lathe's bearings with the existing spindle.

The original bearings were babbitted by using the cast iron shells as the molds. With some babbitt damming compound (a kind of putty) and the use of the spindle as the mandrel, the existing bearings could be re-babbitted.

I'd clean up the existing babbitting and take a close look for damage. If there were shims between the bearing halves, possibly, removing some could give the existing bearings a new lease on life. I.E., remove shims to close up the clearance, then spot and scrape the existing babbitt to conform to the spindle journals. It might not be the most perfect or prettiest show in town, but for this application, would likely do just fine for another few decades. Sometimes, attempting to improve on a simple and very old design does not give as good a result as the original design did in service.

Once again, thanks Joe for the analysis. That's why I posted here, to see if my solution made sense, or there are better ideas !

I've not actually seen the job yet, just the photos. I didn't realize the bearings are a cast iron shell, with a thin layer of "wabbitt" cast inside. Looking at the photo closer I think I can see the joint line between the shell and "wabbitt".
I'll wait now till I get the job before I do or say anything else.

Shame the mods "corrected" my post title, I know it made a few folks smile.
Thanks to all.
Bob

 

[Overland]

This may show the housing / "wabbitt" line more clearly.
The customer said there were some paper shims.
Bob

 

[Greg Menke]

Shame the mods "corrected" my post title, I know it made a few folks smile.
Thanks to all.
Bob

We are widely known for being the moral equivalent of tax form instructions

 

[Overland]

We are widely known for being the moral equivalent of tax form instructions

Oh well, I tried to bring some humor.....
Bob

 

[dkmc]

What's there doesn't "look" bad at all. I'd try to clean/ shim to use it as is if possible. If not, then re-pour them.
Good news is, if it doesn't come out the first time, it can be re-melted and have a second go. Sooty flame as 'mold release'
works well.

 

[Overland]

What's there doesn't "look" bad at all. I'd try to clean/ shim to use it as is if possible. If not, then re-pour them.
Good news is, if it doesn't come out the first time, it can be re-melted and have a second go. Sooty flame as 'mold release'
works well.

View attachment 390106

View attachment 390107

Thanks !
Bob

 

[Overland]

The guy with the old wood lathe came by today, so I could check out what he wants.
This is the first time I've set eyes on a babbitt bearing, so quite interesting.
The bearing shell thickness looks about 40 thou, which really surprised me so thin.
The shells seem quite complete, and still well attached to housing.
He said he measured 1 thou (0.001") out of round on the MT bore inside the spindle.
I'm thinking, what's the problem here ?
He is retired from the machine tool industry where he's used to measuring in tenths.
My suggestion was to assemble it all up and try to measure any lateral/vertical deflection - he can add/subtract shims in the vertical plane.
He was concerned about run out and vibration at maybe 3,000 rpm.
My suggestion again, was set it up, use it and see if there really is a problem here.

Anyway, I get the idea of setting up the shaft and pouring the babbitt metal in to create a new bearing. But I'm thinking you'd have to heat up the whole assembly to get it to flow in such a thin gap, without freezing.
Anyway, once again, I've learned something.
Bob