Looking for odd sized U-Joint for old mower

[JRP3]

I'm trying to help a friend find a replacement U-joint for an old brush mower, don't know the brand, and I can't find a match for all the dimensions. It has internal snap rings, 1.25" diameter caps, 3.7" cap to cap length, 2.94" cross length, 2.27" snap ring distance, and the only markings on it are "B", "USA", and "S".
I found a 1.25 cap and 2.94 cross match but it's external snap ring

https://www.moog-suspension-parts.com/moog-964

 

[Roadworthy]

I ran into that issue trying to redo the PTO dreveline on my mower. I took it to a drive line shop. They replaced the rear yoke now all is good.

 

[JRP3]

I was wondering about getting that Moog external U-Joint with the same cross dimensions but using the old internal clip caps on it. The bearing surfaces on the old caps still look good, maybe polish them on a lathe. Or find new needle bearings for the old joint.

 

[MTGreen]

How exact are your listed measurements and to inside or outside of snap ring groove?

GMB 220-0508 has 1.26 caps with inside snap rings and 2.362 snap ring distance

How to Look Up a U-Joint By Size - GMB North America, Inc.

Don't Have a Part Number For a U-Joint? Do You Know What Size U-Joint You Need? Learn How To Look Up U-Joint By Size Here!

gmb.net

49598-3E300 Kia Sorento 2003-2009

Kia OE Ref: 495983E300, 49598-3E300 Kia Sorento 2003-2006

www.driveshaftparts.com

1.259 caps 2.244 snap ring distance

Universal Joint GUT20)

www.driveshaftparts.com

1.26 caps 2.252 snap ring distance


If you're at 1.250 and you're ambitious/meticulous/determined and have a dial caliper/micrometer and telescope gauges, you could even ream out to 1.260 using an adjustable reamer:
Fancy version:

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Cheap version:

Amazon.com

 

[JRP3]

Or I could turn the caps down to 1.25 on a lathe.

 

[MTGreen]

Or I could turn the caps down to 1.25 on a lathe.

I'm willing to bet the hardness on the caps is considerably higher than the ID of the yoke

 

[etpm]

Or I could turn the caps down to 1.25 on a lathe.

The caps are very hard. You would need to have a very rigid lathe and would need to use carbide to turn them down. I have done lots of hard turning. Really, if you are serious about turning the caps down, you would need good coated carbide inserts with a high quality coating made for hard turning. Like TiCN. And how would you hold the cap? You need to turn the O.D. all at once and it needs to be concentric to the I.D. You could turn a spud that fits the I.D. very well, with only a tenth or two clearance and then hold the cap on the spud with a live center. If your lathe is rigid and stout enough and you have a high quality live center that can take the quite high pressure needed then that could work. And if you only have calipers don't even bother unless you plan on machining oversize so you can sand the cap to fit. Even then unless you are good at making these kind of fits don't bother. You would be better off buying a new yoke that uses a common U-joint.
Eric

 

[JRP3]

I'm willing to bet the hardness on the caps is considerably higher than the ID of the yoke

Good point.

The caps are very hard. You would need to have a very rigid lathe and would need to use carbide to turn them down. I have done lots of hard turning. Really, if you are serious about turning the caps down, you would need good coated carbide inserts with a high quality coating made for hard turning. Like TiCN. And how would you hold the cap? You need to turn the O.D. all at once and it needs to be concentric to the I.D. You could turn a spud that fits the I.D. very well, with only a tenth or two clearance and then hold the cap on the spud with a live center. If your lathe is rigid and stout enough and you have a high quality live center that can take the quite high pressure needed then that could work. And if you only have calipers don't even bother unless you plan on machining oversize so you can sand the cap to fit. Even then unless you are good at making these kind of fits don't bother. You would be better off buying a new yoke that uses a common U-joint.
Eric

All true though I have a friend who is a retired machinist will all the tools and experience needed. However I agree that reaming the yoke makes much more sense. We just have to verify that the internal yoke lock up distance will work with one of the possible metric U-joints listed above.

 

[JRP3]

He decided to go with the Moog external snap ring joint I linked in the first post and will either use the old caps with the new cross, needles and seals or use it as is and tack weld some washers on the outside to act as external snap rings to keep it in place.

 

[etpm]

He decided to go with the Moog external snap ring joint I linked in the first post and will either use the old caps with the new cross, needles and seals or use it as is and tack weld some washers on the outside to act as external snap rings to keep it in place.

If he is gonna use the old cap with the new cross and needles I suggest he needs to measure both the old and new crosses. They should be very close to the same in size. I wouldn't mix the old and new unless they were within 40 millionths of an inch difference. Even then I would only do so if I felt I had to. I can reliably measure stuff to within 20 millionths of an inch, and it is not easy. 40 millionths is a lot easier but still not so easy. Can your guy reliable measure stuff closely? If the difference is any more than a few tenths on the loose side the u-joint will probably not last long because the needles will tend to skid instead of roll. If the fit is too tight the thing will also fail soon. Is there a reason why a new yoke can't be used? I recently had to buy a new yoke for my post hole digger and as I recall it was about 40 bucks. If washers are welded will they fit close enough to keep the cross from moving side to side more than it should? A u-joint cross piece does move side to side during normal operation but this movement is not much. If there is excessive movement it will tend to beat the cups out of the yoke. If a cup beats the washer to the point that the weld breaks then the cup will move out of the yoke and catastrophic failure will be the next fun thing to deal with.

I read my post above and it makes me look like a know it all who is overly safety conscious. After seeing catastrophic u-joint failures a few times they make me nervous. And my career as a self employed machinist involved making some very precise parts so I had to learn how to measure these parts and I had to buy the measuring tools to measure the parts. So at least I know how to measure small stuff. Still, my post makes me look like a know it all. Sorry about that.
Eric