ID finishing Bearing Race

I have a pair of Cylindrical Bearing Outer races. They are 100+ years old (motorcycle engine, NOT HD)rusted etc. The owner had new crankshaft Pins made, and oversize rollers. Yes the bearing is not available anywhere in the world.
So the outer race needs to be enlarge .025. I have soft jaws which cover 2/3 the circumference, a couple light passes with solid carbide BB, grinder.clean up the rust pockets, show lots of hard spots in the race.

I do not have an internal grinder on the MG12 grinder, so the EE has to handle the job, with a Themac Tool post grinder. Practicing to find the setup for the final sizing, The setup is workhead 50RPM, 3/4 wheel at20K, 32A60 k5vbe.
infeed of .0042 per/rev.

The finish is far from what I expect from a surface as hard as this. Will I need to lap this to size and finish.

Ideas please.

You need to consider the roundness of the race OD, ditto the mating bore, and further what fit of race/roller/race (or journal) you're shooting for. Even with good support by the chuck, if you distort an out-of-round race OD you'll have a bad ID when released from the chuck.

How did you true the grinding pin? Have you checked runout and balance on the grinder spindle? Can you take a short video with good closeups of the process?

50 rpm seems very slow for the workhead. Could that be contributing?

Did something similar a couple of years back, also for a circa 100+ year old bike engine, my case it was a bronze roller cage, the ID ran on the crank shaft, OD i was down to make, but kinda hit the jackpot and found a damn near perfectly sized needle roller bearing outer race way. There a common thing and available in one hell of a lot of sizes, in my case it saved all the pain your going through. To make it work we had to go to a slightly odd sized rollers but they were also easy to get hold of.

Finish is everything, if you want it to last - hold up it has to be like the ID of a typical roller bearing way, for a part like that i would expect honed at the least to a pretty fine finish, as much to remove the errors from grinding as to improve the finish.

Whoa!! What's that feed again? Or do you mean traverse?

tdmidget said:

Whoa!! What that feed again? Or do you mean traverse?

Click to expand...

Two tenths infeed is normal on an id grinder but not "per revolution." That would be insane. And 50 rpm does sound really slow.

If it wuz me, I'd ditch the original races and make new ones. In the long run it would be easier. I'm assuming these are for the crank throw, not the shafts ? On the shafts, easier and better to make new shafts that fit some off-the-shelf roller and ball bearings. Then in the future they could be replaced easily. Plus making your own antifriction bearings is not a simple task.

Given the way he is doing this, I'd want to hone it. Lapping is a no, can't make the parts round and straight. But really, easier and better just to make new races (unless you can find an off the shelf part, like adama suggested.) The material from something 100 years old is not gonna cut it.

If the material is suspect, how hard would it be to make new from scratch ?

From a good, clean, known material.

Thanks all for the ideas. These bearings are not for crankpins, but the crankshaft. The rollers run on the shafts, no inner race, and the shafts are new. Yes it was traverse of 4.2, feed is .0002-4.
I have speed the workhead to 100rpm, slowed the traverse to.0025, and looks much better.

This is an engine without a bike, so it may never hit the street, may someday run on a stand. But regardless I want it right.

Now the owners buddy who I also made parts for, rode them from Atlantic city NJ to San Diego CA in the Cannonball run 2 years. To enter your bike had to be at least 100 years old, it was a 1913 Thor. 3400miles at 30mph and less.