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Sheldon Bull Gear Busted Teeth

Frank R

Stainless
Joined
Dec 18, 2009
Location
Dearborn, Michigan
20211002_094328.jpg

This guy I know just bought a Sheldon 11" lathe. It will clean up well and he got it for a very good price. However, the bull gear has five missing teeth.

He just missed a replacement spindle assembly on eBay that went for $40.

Would anyone here like to make a new gear for him? Or does someone here have a replacement gear? I know the cost will be substantially higher than $40.
 
That lathe has the opposite problem from the 10" Sheldon I recently got - On mine, the bull gear has one chipped tooth, but the small back gear pinion only has 4 teeth left !
 
The problem looks similar to on my Rivett. Cast iron bull gear, at least the breaks look like that.

Fill it with braze, turn to size, and recut the gear teeth.

On the Rivett, there were quite a few missing from the bull gear, the pinion had no teeth at all. The only good gear in the lot was the driver on the pulley.

I bought a second headstock to get a new bull gear and back gear assembly (also cast iron). I may shrink steel rings onto the old one and cut teeth in the rings, but there was enough to do without messing with that.

Rivett being Rivett, the bull gear did not quite fit, and the back gear assembly did not either. But neither was that hard to make fit without any bodging of parts.
 
Years ago a guy here used to offer to repair gears. I had him do a back gear for a SB9 and he did a wonderful job. He turned off all the teeth, pressed on a new ring of steel and cut all new teeth.

I am hoping he is still around and would be willing to do that.
 
The good news doing that is that you replace what may be cast iron teeth with steel teeth, which are less likely to break.

The big issue with many such gears is whether there is enough meat on them to do the job. Some, such as the OP's, have the inside undercut for various reasons, and there is not a lot of rim to hold a ring after turning off the teeth plus enough more material to give some "base" to the new teeth.

The picture shows that there may be just barely enough to do the ring, but it will be really close. You need enough "base material" to stand the press fit. A snug "loctite fit" may be less dangerous, and with all that area, if the ring idea can fit, loctite should hold well..

The Rivett has a ring of index holes in the rim, and the rim is not thick. It may be possible to get a ring onto it without losing the index holes, but it will be close. I opted to replace it for that reason.

The thickness issue is why I like the braze and recut plan. Also, there are not that many teeth missing, so the ring is a bit of overkill, steel or not.
 
You would be best off to make a new gear from steel. All it takes is a milling machine, a gear cutter and an indexer. I did that for a 13" Sheldon that I sold to Projectnut. Ask him how its working.

Tom
 
Th
The thickness issue is why I like the braze and recut plan. ....

The section there is really thin, yes. My approach would be to trim the broken teeth (looks like 7 missing or damaged) and silver solder in a cast iron blank. Then turn the blank to the OD and go to work cutting the teeth. It's pretty tough to blob on brass weld material over that large an area and make it really structurally sound. Also the region of damage looks pretty munged up, it might be tough to get really good adhesion.

I've re-made entire gears like that from scratch, sometimes that's the best way.
 
All it takes is a milling machine, a gear cutter and an indexer.

Could I remove the head stock from the lathe and bolt it to the mill? And use a metal finger to engage the good teeth to keep the gear indexed in the proper position without using an indexer?

I would have to grind a single point bit unless I could turn the head stock sideways and use an involute cutter.
 
First we next to find out what tools you have to work with. Vertical/horizontal mill, size/make, rotary table (y/n), what else?
If you don't want to make a new gear then I think the next best thing is to remove the gear from the spindle mount it on a rotab, mill away the damaged area. Make block steel the width of the teeth with an inside radius to match the cleaned up section of back gear and a OD the same as the existing gear. Layout where the new teeth are going to be and drill one or two holes through the blank in the spots between the new teeth. These will be where silver solder will be fed during the bonding of the blank to the gear. I would fasten the blank to the gear with a couple of screws. Thoroughly coat both the blank and gear with black silver solder flux during assembly. Put .001 or so shims between the blank and gear. This to allow for the flow of the silver solder. These can be removed once the blank is secured in position. The next step is very important. Heat the entire gear and blank assemble to a red heat. This will take some fixturing. When at temperature, feed solder into the holes that were drilled until solder flows to the edges. Continue this until the entire blank is soldered in place. Next step is also critical. Pack the gear in ashes to allow the gear to cool slowly, preferably at least a day. Failure to do this may result in a cracked gear. Clean, cut the new teeth.

Tom
 
Thanks.

I am leaning more toward the brazing method. If I have to do this myself I am looking at the easiest method of doing it in order to get this older lathe running at low speeds. I do not have the ability or tooling to do it the way you mentioned.

I am tempted to just insert some pins and hand file them down until a gear comes up on eBay.
 
Have you checked out the Sheldon lathe io. group ?
You could post a WTB ad - Maybe someone has a parts lathe ....
 
Thanks.

I am leaning more toward the brazing method. If I have to do this myself I am looking at the easiest method of doing it in order to get this older lathe running at low speeds. I do not have the ability or tooling to do it the way you mentioned.

I am tempted to just insert some pins and hand file them down until a gear comes up on eBay.

That works, a time-honored method. You could probably get three pins across the width of that.

SF_gear01.jpg
 
Have you measured the gear? It's just a gear...there is a chance you can find another that can be modified to fit. It's going to have to come out to be fixed in any case so I'd start by finding out exactly what you need. A few years ago I bored and sleeved a bull gear for a fellow forum member.
 
Have you measured the gear? It's just a gear...there is a chance you can find another that can be modified to fit. It's going to have to come out to be fixed in any case so I'd start by finding out exactly what you need. A few years ago I bored and sleeved a bull gear for a fellow forum member.


Pretty good odds that gear is not "just a gear".... they are often integrated with portions of a sleeve, etc, and recessed fairly deeply to clear things, allow access to the pin, etc.

At the least, it may need to be thick enough to take the recessing, and provide a good large diameter hub.

The pulley gear is generally "just a gear" aside from the large diameter hub
 








 
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