SB 9A Horizontal Drive Unit Pulley Shaft Heavily Scored

mbouchpcp · Dec 18, 2015

Oil was leaking from the collar side of the pulley shaft housing (the one with the 10 inch pulley driven by the belt running to the motor part # AS1960N3).

I pulled the shaft. I discovered the unit does not have bronze bearings and that the pulley shaft is heavily scored for 2.5 inches from the pulley inward.

I have little if any mechanical experience and am new to turning metal. That being said should I:

a. just replace the felt wick and reinstall the scored shaf (with the understanding that drive units without bearings eat shafts)
b. turn a new shaft and install it with new felt wicks
c. bore out the shaft housing, insert a thin bronze busing, turn a new shaft, and reassemble everything
d. other

I understand C is probably the "correct" answer but is that overkill?

Thanks.

iwananew10K · Dec 18, 2015

Might sound weird but if it was still working well, and only leaking oil then just keep adding oil, it may eventually fail, or it may last just fine, even if it does fail the repair will still be the same so it's essentially no loss either way.

In the meantime develop your skills so when and if the time comes you can make a proper repair.( which would be your C option, only just buy TGP shafting to size instead of turning it yourself)

thenrie · Dec 18, 2015

If the bore is badly scored all the way through, you may need to consider bushing it, but I just took mine to a machinist, who said what iwananew10k said. Mine was scored on the ends of the right-side bore, but it was good in the middle. I replaced the shaft with a new TGP 1045 shaft from McMaster-Carr. Cost me a whopping $12 and change. Keep using the old shaft while you trim and finish ends of the new shaft, drill the dimple for the step pulley, and you're good. By the way, getting the old drive pulley off was a bear. Those taper pins are tough sometimes. Use a big hammer and the right size punch.

Big Gem · Dec 19, 2015

thenrie said:
If the bore is badly scored all the way through, you may need to consider bushing it, but I just took mine to a machinist, who said what iwananew10k said. Mine was scored on the ends of the right-side bore, but it was good in the middle. I replaced the shaft with a new TGP 1045 shaft from McMaster-Carr. Cost me a whopping $12 and change. Keep using the old shaft while you trim and finish ends of the new shaft, drill the dimple for the step pulley, and you're good. By the way, getting the old drive pulley off was a bear. Those taper pins are tough sometimes. Use a big hammer and the right size punch.

Yep, that's one where the taper pin ends look the same size. Clean them off, even gring them with a Dremel if need be so you can measure the diameters and make sure you're driving out in the right direction. I saw one where the guy guessed wrong and drove the pin tighter. It split that cast iron hub pretty nicely. If the pin isn't out after about 5 hits, consider drilling it; they're soft.

I second that idea about the big hammer. I don't know why this is true, but a slow moving 3 pound hammer does a better job than a fast moving 1 lb hammer.

mcruff · Dec 19, 2015

Drive units without bearings shells do not eat shafts, yours may have but mine are both 1940's models and both are in great shape. Yours was just not taken care of.

tribologist · Dec 20, 2015

The shaft was made from very soft steel and is sacrificial. Unless the bores are really bad you can buy a rod of 12L14 steel and make a new shaft. To help it wear in you can put some moly assembly lube on it. Also replace the wicks.

thomasutley · Dec 20, 2015

If you do have to drill a taper pin, and it's pretty common to have to, only drill about 2/3 through the length of the pin from the small end. That leaves a little "bulkhead" inside the pin to drive it out with a small flat-tipped punch. Driving from that point within the pin stretches it and makes it smaller. Usually does the trick.

Once it's out you'll need to replace it with a new one. They're cheap on Amazon. You can also buy taper pin reamers to enlarge the hole for the next size up if necessary. Reamers are less than $10 usually.

mbouchpcp · Dec 20, 2015

thomasutley said:
If you do have to drill a taper pin, and it's pretty common to have to, only drill about 2/3 through the length of the pin from the small end. That leaves a little "bulkhead" inside the pin to drive it out with a small flat-tipped punch. Driving from that point within the pin stretches it and makes it smaller. Usually does the trick.

Once it's out you'll need to replace it with a new one. They're cheap on Amazon. You can also buy taper pin reamers to enlarge the hole for the next size up if necessary. Reamers are less than $10 usually.

Taper pin was stuck tight..... for awhile. Small hammer and short punch efforts were unsuccessful. I ground both ends down flush with the pulley. I then used some heat on both ends of the pin. Moved on to a 5 pound sledge hammer and a 10 inch long punch I found in the bottom of my tool box. Five whacks and the pin fell out. There was some rust on the pin so I figure that was making things tight.

Shaft removal also turned into a more than expected effort. It would not budge. I heated the shaft on both sides of the pulley and used the sledge hammer and punch again (note the large handle end of the punch was seated against the shaft). Another 5 whacks and the shaft fell out. It too had rust.

It's amazing what happens when proper tools (bigger) are used.

mbouchpcp · Dec 20, 2015

thenrie said:
If the bore is badly scored all the way through, you may need to consider bushing it, but I just took mine to a machinist, who said what iwananew10k said. Mine was scored on the ends of the right-side bore, but it was good in the middle. I replaced the shaft with a new TGP 1045 shaft from McMaster-Carr. Cost me a whopping $12 and change. Keep using the old shaft while you trim and finish ends of the new shaft, drill the dimple for the step pulley, and you're good. By the way, getting the old drive pulley off was a bear. Those taper pins are tough sometimes. Use a big hammer and the right size punch.

I picked up six feet by 7/8" of 4140. I'll either use it as is or I'll turn one end down to 3/4 and bush it with 7/8 by 3/4 bearings that McMaster has available.

tribologist · Dec 21, 2015

If you are using a harder material like 4140 you probably should bush it. The original shaft is leaded low carbon steel that will not eat the cast iron. 4140 will wear cast iron faster.

iwananew10K · Dec 21, 2015

why would a harder polished material wear cast iron faster?
ie- hardened,polished spindle running in cast iron bearings?(like the head stocks)

This concept seems totally foreign to me but I am prepared to learn something.

FWIW- I had a busted 9" countershaft pulley that I salvaged the shaft from, I cannot say if it was original but it was definitely not leaded steel- 1045 would be my guess.

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