Boring a Bearing Race

[armscor 1]

Yep I had a TL 250, had to buy the bearings from Honda but that was 20 years ago, very annoying and expensive.

[mcman56]

I did not get very far. The race is 60 mm id and 80 mm od plus has a groove for the balls. I mounted and trued up in a 4 jaw but when running an indicator on the outside, I can see that the race bulges out .0005 between jaws. That is only going to get worse when cutting. I don't think it is clamped too tight but my tightness calibration/ feeling is based on a 3 jaw chuck. A thread is involved but does 4 jaw have 4 x 1 the clamping force vs 1/3 x 3 gripping strength for the 3 jaw? 4x the gripping/ distortion force when tightening with a key relative to a 3 jaw would produce a different result. If so, how would you compensate? (not that it would help here. I can see how a specially machined collet would help but it would be more work than machining a ring from scratch)

[whateg0]

It absolutely can and will distort a hollow part like that. Don't believe me? Take it out, rotate it 45 degrees to the now-high spots, and re check. This is one of those situations where "somebody" will say soft Jaws are king.

[Harold_V]

This is one of those situations where "somebody" will say soft Jaws are king.

Chuckle!
I was about to respond to the previous post, but decided to read all others before doing so. You seem to understand my mindset, as that's exactly what I was going to do.

Assuming turning the bearing race was important, and had to be done, yes, soft jaws. I'd use jaws wide enough (pie jaws) to enclose almost the entire race, so it had no place to distort. By doing so it could be kept round, and if the jaws were properly prepared, concentric.

It is quite easy to distort a bearing race. They 're hard, and can shatter, but that doesn't prevent them from distorting. I learned that lesson the hard way when I used a pair of bearings on the jib crane I built for my foundry area. The moment they were loaded, they broke. The snap was deafening, if you know what I mean. They were replaced with equivalent sized solid steel rollers and work perfectly well.

H

[Bill Shields]

As someone mentioned earlier-> this is going to go badly.

Faceplate with a recess machined to fit the ring.

Clamp longitudinal with another ring.

it is going to be easier to start with a piece of solid bar and cut it off when done.

[whateg0]

This is one of those situations where "somebody" will say soft Jaws are king.

...

It is quite easy to distort a bearing race. They 're hard, and can shatter, but that doesn't prevent them from distorting. I learned that lesson the hard way when I used a pair of bearings on the jib crane I built for my foundry area. The moment they were loaded, they broke. The snap was deafening, if you know what I mean. They were replaced with equivalent sized solid steel rollers and work perfectly well.

H

On the casters I made a few months ago, I bored the parts before welding. They were meant to be a slip fit, to be secured with loctite "bearing glue". The test piece worked perfectly. The last one though came out 5 thou egg shaped. I pushed the bearing in anyway since there was only a bit over 1 thou of interference. As these were double row ac bearings that was enough to cause a very light cogging. Not enough to prevent the caster from rotating from its own weight, but enough for me to feel it. For the application, it's fine, but next time I'll probably figure out a way to bore it to final size after welding.

[Harold_V]

Yep! I've yet to do any welding that didn't result in at least a small amount of distortion. I have learned to clamp things in place before welding, however, and that seems to restrict movement considerably. I leave clamps in place until the weldment has cooled substantially, which seems to keep general alignment.

H

[tornitore45]

Take a solid bar longer than the bushing you want to make
Chuck it sticking out more that the bushing depth
Bore, finish OD
Part off
No distortion, the chuck is biting on solid core

[mcman56]

I have been looking at DOM 1026 Steel Tubing because it comes close in size so I could just do some minor cuts on ID and OD. Will tubing tend to distort out of shape more that solid bar when machined? Would there be an advantage to solid bar?
https://www.strangeengineering.net/prod ... foot.html/

[Bill Shields]

see Maurio's comment...been there -> done that...learn from exprience

[Harold_V]

Would there be an advantage to solid bar?

The real advantage to solid bar is what was mentioned by Mauro.
Any time you must grip a thin wall, and ¼" wall at that diameter certainly qualifies, unless the work piece is perfectly round, nesting in an identical diameter (that's why boring soft jaws is a critical operation), you can expect some distortion. By gripping a solid piece, none of the gripping force is transferred to the work piece.

While machining surfaces has a tendency to relieve stresses, often causing the machined part to distort, with lathe work, where the surfaces being machined tend to be uniform, that is often not an issue, as the internal stresses tend to be concentric with the material, so movement is uniform. Still, to guarantee the best possible outcome, one is well advised to learn to rough, then finish work. By doing so, any movement due to stress relief will be corrected by the finish cuts. This is simply good shop practice.

H

[Richard_W]

I regularly cut hardened drill bushings. I have been have good luck with a cermet cnmg432 and smaller bushings ccmt3252. Speed of around 150 SFM and a .001 to .0015. Run dry. Ceramic works well if there are no interrupted cuts. The idea as explained to me is the cutting pressure anneals the material the first revolution and cuts what has been annealed the second revolution. This is what I use since the company provides it. I can hold +/_ .0005 easily enough on a worn out Haas CNC lathe. Generally if you can hold a close tolerance on your lathe, then you should be able to do the same doing hard turning. Although it takes a few cuts to learn how your machine reacts to the different tool pressure than you are use to cutting. I have done the same on a manual lathe. Some part runs are as high as 50 parts that I do.

Richard W.