Driving New bearing on shaft......TIGHT! What are my options?

musicinabottle · Apr 20, 2017

I have the arbor out of my table saw for bearing replacement. Old bearings were so tight on the shaft that I had to surgically destroy them of the shaft with a small grinder. Putting the first bearing on and about 1 inch on and it's ridiculously tight to the point that I'm beating on a socket slipped over the shaft on to the inner bearing race and I'm beginning to mushroom the top of the cheap socket. So operations have stopped! I'm contemplating chucking the shaft up in my drill press and holding something nice and square up to the shaft below the bearing with some 100 grit abrasive paper or........ would it be better advised to have someone work off a bit of material on a lathe? Fearful of destroying the shaft by getting it out of true, this being a critical component of high rpms. What to do?

Bob-J-H · Apr 20, 2017

Have you heated the bearing and cooled the shaft? Bob

musicinabottle · Apr 20, 2017

I did with the old bearings with no luck. You can literally see scrapes down the side from the original bearings installed. I brought in not only the old bearings into the bearing supply house in Spokane Washington, but also the shaft, all of which were mic'ed.

sealark37 · Apr 20, 2017

What Bob Said. You may help the process by polishing the shaft to remove any small defects with 600+ emery cloth. Dry ice for the shaft, and moderate heat for the bearing will help. Regards, Clark

rke[pler · Apr 20, 2017

Mic the shaft for size, repeat around the shaft to account for a lobed shaft. I've seen this where you couldn't get a bearing on and the shaft mic'd good all the way around - at that point you have to put the shaft in a v-block and spin it with an indicator over the top (and that won't work with all kinds of lobing possible).

If it's more than .001 off you might use a file to clean it up, less than that you can likely polish with emory. Irregular is harder to deal with as you need to take a little at a time and remeasure to check for improvement.

Flail · Apr 20, 2017

Above suggestion of polishing the shaft, cold to shaft and warm to bearing. Then don't beat on it. Find someone with a press and then press against the inner race. Hammering, you risk hitting the outer race and brinelling the bearing or mushrooming the end of the shaft.

keithmech · Apr 20, 2017

Grind off the new bearing and start again.Remove all high points on shaft.
A fill works well for this job.Emery will mostly follow the humps/bumps and remove metal everywhere.Installing the bearing works way better in a press.
Lube up the shaft with some light oil and smear the inner race with oil as well.It was tight originally for a reason.

musicinabottle · Apr 20, 2017

I'm using a socket that fits right over the shaft and touches only the inner race of the bearing and I'm lightly tapping it. It will go, there's no doubt, I was just wanting it to slide a bit easier when it comes time to replace them again. One of these bearings comes up against a large thick washer so no hope of getting in there with a puller. The fella who ran over my old table saw and destroyed it does have a very nice lathe so........ Thinking about getting his people to take this thing down a bit.

musicinabottle · Apr 20, 2017

keithmech said:
Grind off the new bearing and start again.Remove all high points on shaft.
A fill works well for this job.Emery will mostly follow the humps/bumps and remove metal everywhere.Installing the bearing works way better in a press.
Lube up the shaft with some light oil and smear the inner race with oil as well.It was tight originally for a reason.

TRUE! I'm 50 years old and if I knew the new bearings would last longer than me, I'd just press them on. Maybe I should drill 2 holes through the arbor stop, one on each side of the shaft and then I'd have something to reach in there and knock off the old bearings again.

michiganbuck · Apr 20, 2017

You might hone the shaft to bring it down to original condition.. honing does not take stock or change the run out.

QT: [ to have someone work off a bit of material on a lathe? at mid speed a hone on the lathe or by hand IMHO.

Turning on a lathe and a fine file might do well...Hand file or hone by hand would be my way.

Possible oxidation, bugs or rust is the problem.
Perhaps a 16 oz hammer with a drop weight not a heavy slam.. with pushing down on the driver. bearing should go with every drop.. locking up then likely too tight. Yes a machine hammer not carpenters.

keithmech · Apr 20, 2017

make the bearing loose on the shaft and now the shaft pounds out.Why did they have to invent fits?.So much easier when you could just guess and hope for the best.

michiganbuck · Apr 20, 2017

Agree don't want it loose just cleaned up to original..should even leave a little witness of original size.

gorrilla · Apr 20, 2017

musicinabottle said:
I have the arbor out of my table saw for bearing replacement. Old bearings were so tight on the shaft that I had to surgically destroy them of the shaft with a small grinder. Putting the first bearing on and about 1 inch on and it's ridiculously tight to the point that I'm beating on a socket slipped over the shaft on to the inner bearing race and I'm beginning to mushroom the top of the cheap socket. So operations have stopped! I'm contemplating chucking the shaft up in my drill press and holding something nice and square up to the shaft below the bearing with some 100 grit abrasive paper or........ would it be better advised to have someone work off a bit of material on a lathe? Fearful of destroying the shaft by getting it out of true, this being a critical component of high rpms. What to do?

If you check the bearing book, they should have the PROPER fit for the bearing, so I'd assume you have that, or should have. If the old ones wouldn't come off, you may have an oversized shaft to begin with. Table saw needn't be so tight as to require some super tight bearing fit.
I'd would expect a table saw shaft to be no more than 1", probably more like 3/4", or even 5/8" SO a few tenths should be all that is required. Polish that puppy till it's maybe .0002/.0004 OS, press(NOT HAMMER) your bearing on, and go to sawing. This shouldn't be rocket science.

Bill D · Apr 20, 2017

Any reason not to knock a little off the diameter between the bearing bosses? often only the two ends need to be exact. the middle can be filed or ground down to a loose slip fit.
Bill D

SIP6A · Apr 20, 2017

Your obviously not using a big enough hammer.

Lakeside53 · Apr 20, 2017

Temperature differential... I just had to put on a bearing on a 2 inch shaft 2 thou oversize. Shaft in freezer for a day and heated the bearing to 260F. Tapped on nicely.

Gordon Heaton · Apr 20, 2017

Lakeside53 said:
Temperature differential... I just had to put on a bearing on a 2 inch shaft 2 thou oversize. Shaft in freezer for a day and heated the bearing to 260F. Tapped on nicely.

That’s fine for a 2” bearing. The smaller you go, the tougher it gets to make temperature differentials effective even though the interference gets smaller.

musicinabottle · Apr 20, 2017

SIP6A said:
Your obviously not using a big enough hammer.

actually using a 3/4 inch Craftsman wrench. Should I step it up to a 7/8 or 15/16 perhaps?

Lakeside53 · Apr 20, 2017

Gordon Heaton said:
That’s fine for a 2” bearing. The smaller you go, the tougher it gets to make temperature differentials effective even though the interference gets smaller.

It's linear. 2 inch at 2 thou is the same as 1 inch at 1 thou. Same rate per temp differential. The bigger problem is measuring accurately and shaft surface finish. A 1 inch bearing will move about 6-8 10ths per 100F, 1/2 inch 3-4 10ths, etc. Measure accurately, plan accordingly and you can get the desired fit without violence.

Obviously you wouldn't use 2 thou fit on a typical 1 inch bearing; even 1 thou is pushing it even for a taper roller. The manf data tells the max allowed and among many variables and fit requirements, factors in bearing tolerances.

Gordon Heaton · Apr 20, 2017

Sure. That’s the book answer, but other things are in play too, like relative mass/heat holding ability etc. Try it- do a 2-incher and then a 15mm and you’ll see the difference. You’ll need to be damn fast with the small one and if the tight fit is on an extended length like the OP has it won’t help at all.

Driving New bearing on shaft......TIGHT! What are my options?

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