Cleaned and greased the BB on my "new" 73 Raleigh Competition and found one of the spindle bearing surfaces is pitted/eroded, probably about 1/3 of the circumference. It's a 3 arm TA Pro 3 crankset.
It's marked "TA 344" on the spindle - looking on Ebay, the price for a replacement is unreasonable.
The spindle is 114.5 mm wide with a 5 mm difference between drive and non-drive side.
Looking around the web, it appears that most agree the taper is more or less JIS. Someone said they put a 115 cartridge BB in and it worked fine.
I was thinking about trying a 116 with 2-3 mm of spacers on the drive side, should get me in the ball park.

I likely won't be putting a lot of miles on this bike, what would happen if I just ran the pitted spindle and keep an eye on it every season?

One consideration with this approach (which I otherwise think is a great way forward) is that a cartridge bottom bracket needs the NDS cup to make good contact with the rest of the unit to support it properly. Many of Shimano's cartridge BBs come with a NDS cup that looks like this:



So you can see that if you scootch the main unit too far to the right with spacers, that ledge on the end of the NDS cup could bottom out on the BB shell before it can make contact with the other part. You know?

One way around that (especially if you plan to use 5mm worth of spacers anyway) would be to buy a cartridge BB intended for a 73mm bottom bracket shell -- then the math would work out fine. Another way would be to get an NDS cup that doesn't have the ledge on it, like this:



With that guy, it can just keep threading into the BB shell until it finds its way to the cartridge. It looks a little weird in the end, but works just fine!



I have a tendency to harp on this topic, but that's just 'cause I want to make sure these things work out for people.

That's okay with me. I hadn't thought of that.

Bumping an old thread: I'm having trouble finding a cup with no ridge that will fit a UN-55. Can I just grind the ridge off of the original cup?