I'd like a tube of Nu-Thread please

You could re-thread it smaller, but you gots a whole heap of dis-assembly and inspection to do first!  Bearing surface is prolly buggered up, too...

DiyDave wrote: If the bearing surface is OK, Here is what I would do:  Put a bushing in the center hole, and take a new hole saw, and cut off the old threads, then re-thread it.  Important part is sizing of the hole saw, and finding a standard size fine thread die.  I'd try them out on a sacraficial piece of aluminum scrap shaft.  Still gonna be a bugger to get it started straight...

More pictures: Today I removed the outboard bearing cage. The bearing surface on the sprocket shaft is not damaged. The threaded area is 0.10 undersize. I can file the shaft so it is below 60 Rc. I am considering welding the shaft and recutting the 1 1/2-12 thread. To do this I need to move Allis to where I can weld. (sugestions ???) I'm considering TIG welding with 304 stainless rod. I have had luck welding on high carbon steel without the weld cracking. (sugestions)

If I have to take the shaft out I will look for another shaft. This machine has the 3 3/4 sprocket nut. I think this means it has the 20 spline shaft. I am making an oak bearing that I will soak in oil so I can move the machine to work on it. I don't want to split the track, disconnect the truck frame to roll it out of the way so that I can remove the sprocket. The concept of cutting the truck frame and welding it back together rubs me the wrong way. I do appreciate any comments.

You could take a portable boring head and turn boring bar around and turn shaft to thread size. Use an acorn type die and thread the shaft. All of this would need squaring of mill to work piece. There is plenty of room to do it there also.Probably easier this way than dismantling machine. Might even rent the mill. HTH Tracy Martin

Cant get the bearings down here anymore so we use one with the same bore for the shaft, but larger O.D. which means machining housing out to take it. All very expensive. If you can get a good one from a tractor salvage yard would be best cost wise, even if you have to look a long way out of state. An old timer on AC crawlers told me they cannot lube properly with that drip feed from final drive. He showed me how to put a grease zerk on the end cap where it recesses a bit to protect it. Use grease with no fancy additives so it will blend with the final oil if over greased he said. In the years I followed his advice, I never again had an outboard bearing fail  (HD6 and HD11 tractors)

Edited by Mactractor - 29 Aug 2014 at 10:08pm

The repair is complete. I made a fixture that locates on the bearing surface and holds my diegrinder to cut the damaged threads down to a smaller sized thread. The fixture is adjustable for cutting the shaft diameter using a carbide burr. It is manually rotated and translated on the bearing surface.
The original 1 1/2-12 thread was recut 1 7/16-12. This is a standard size but I was unable to find one. I located the 1 7/16-12 tap and die on eBay. I made the special castle nut.
I made the die stock to locate on the bearing surface so that the thread would be aligned properly. I cut a 1/8 NPT thread in the bearing cap to pre lubricate the bearing. Thanks to everyone for comments.

I really like that ingenuity... Better hang that handy dandy tool up on the wall for the next time somebody has the same issue with theirs...  Then rent it out and make a fortune selling those "special nuts"   I like the die grinder idea too, but I think I would have opted to have a carbide cutter to be put in the tool you made for cutting the threads down, then put the die in and finish the job... I applaud you in your success. Best part, you had pictures to show too...

Wow, that is impressive!