Bearings rough after new install on Roll-in saw

I installed new blade guide bearings on my Roll-in saw. The blade guide (roller) and bearing is pushed out the back of the assembly via a small access hole. Otherwise, the bearing sits in a blind hole.

On install, I pushed the bearing on to the blade guide shaft first, applying pressure only to the inner face. The blade guide is ground with a small boss that sits on the inner face of the bearing to provide clearance for the blade guide and outer race. Consequently, I applied a couple shims to take up the space between the blade guide and outer race, and pushed everything in place. As you would expect, it didn't take a huge amount of pressure.

These bearings are double row 5201-2RS and are designed to take some angular force. When testing the bearings by hand after installation, I was surprised how rough they feel (or, "notchy" if you prefer). It ranges from just detectable to VERY rough. I realize some bearings will feel rough without a proper preload. Also, some high-end bearings with special grease feel a bit odd. But, for the worst one, I've never felt anything this bad in a "good" bearing.

The bearings I selected are "C3". Perhaps that makes a difference. Or, perhaps I damaged the bearing on installation. If so, I can't figure out another way to install them into a blind hole. The inter race of the bearing doesn't touch the back of the assembly. So, I can't install the bearing first, then press in the blade guide. Seems like that would be worse than my sequence.

As usual, I'm in a hurry to get the machine back in service, so any thoughts would be appreciated.

Sounds like either bad or buggered bearings

If it was me I'd press the bearings on the guide rollers by the inner track (as I think you did) then heat the housing the outer tracks fit in to (it shouldn't take much, so not enough to damage the bearings.

Limy Sami said:

Sounds like either bad or buggered bearings

If it was me I'd press the bearings on the guide rollers by the inner track (as I think you did) then heat the housing the outer tracks fit in to (it shouldn't take much, so not enough to damage the bearings.

Click to expand...

Not a bad idea. I do have another set of bearings. Maybe wrap the housing in Aluminum foil and heat up in a toaster oven to 250 or so. Might be worth the time just to see if the bearings really are damaged. I usually don't bother to heat anything when installing bearings because I can press directly on the proper race. This is one case where that isn't possible.

Did you happen to turn the bearings before installing them? If so, did they turn smoothly then? Don't suppose you measured the fits? Something sounds weird with this - it sounds like you did just fine procedurally on the installation otherwise. About the only time I've ever had something like this happen was when someone installed bearings with way too much interference fit. They felt rough, tight and bumpy like you're talking about. I took a set back apart once and found something like .004" interference fit on the (1/2") bearing I.D.s - fixing the fit solved the problem.

Good point eKretz.

eKretz said:

Did you happen to turn the bearings before installing them? If so, did they turn smoothly then? Don't suppose you measured the fits? Something sounds weird with this - it sounds like you did just fine procedurally on the installation otherwise. About the only time I've ever had something like this happen was when someone installed bearings with way too much interference fit. They felt rough, tight and bumpy like you're talking about. I took a set back apart once and found something like .004" interference fit on the (1/2") bearing I.D.s - fixing the fit solved the problem.

Click to expand...

The bearings did turn smoothly before installation. I did not measure anything before installation.

I called Roll In and discussed the issue with them. They were stumped too. They press the bearing on to the blade guide, then press that assembly into the guide housing. This obviously applies a significant force to the inner race as the outer race is forced in place. The guide housing is not heated prior to assembly and they said it should not be necessary.

I removed the worse bearing and it rolls smoothly after removal. So, the problem likely involves the extra clearance of a C3 bearing, or you're on to something eKretz. I happened to have a couple "non-C3" bearings laying around so I pressed them in. They are WAY smoother. Still not a smooth as you'd expect, buy much better.

I've installed a decent number of bearings in various machine. Often, the inner race is a tight fit. However, the outer race can be slipped in with little effort. I suspect the tight fit may be the source of the problem. I eventually found two more bearings in my shop of the correct size and I'll install them tomorrow and take some measurements before installation.

For something that size you shouldn't have more than a couple ten-thousandths interference. Let us know what you find when you measure.

sounds like the bearings are either too large diameter or too small ID on the machine. accidentally pressed in a bearing 4 thou too small of a bore and just about destroyed a bearing as it didnt turn at all after from being compressed.

Sorry for the delay getting back to this issue. Been too busy lately.

I measured the size of one hole in the guide and it's exactly 2 thou undersize. However, this hole was already related to the "smoothest" running bearing of the four. Earlier, I pressed new bearings into the guide with the "roughest" running bearings to see how they felt (before I decided to measure). They are still a little rough but probably acceptable.

I'm going to go with this for now. Bearings are cheap and easy to replace so I'll revisit the issue later when I have more time. Another guy reported pressing some bearings into the wheels on a Roll In saw and they were 3 to 3.5 thou undersize. Maybe Roll In just likes undersize holes. If I were to guess, I'd say some of the worst holes are definitely more than 2 thou undersize...which is way too much for a small bearing. Anyway, now that my milling machine is back in service, it's an easy fix down the road.

For what it's worth, I talked to Roll In and they press the bearing in by applying pressure directly to the guide roller (i.e., no shims like I used to apply some pressure to the outer race).

I purchased this saw from the original owner, a machinist who used the saw very little. But I'm hearing a lot of "rumbling" from the gear box. I've heard the same noise on some saws on youTube. However, I'm a little suspicious of this noise. The key on one of the pulley's was very lose but that didn't completely alleviate the noise. So, on to the next issue I guess.

I don't think one should ever press a bearing into place on a shaft by pushing on the outer race, or into a housing by pressing on the inner race. That can damage the bearings or races.

abstruse said:

I don't think one should ever press a bearing into place on a shaft by pushing on the outer race, or into a housing by pressing on the inner race. That can damage the bearings or races.

Click to expand...

well, it depends entirely on the fit. if its a slip fit and you are securing things with Loktite 620, no need to worry what you are pushing on, right?

If the bearings have high clearance you can get away with a little more interference before it causes trouble. It sounds like you found the issue.

I wonder if it's possible that the casting has shrunk or distorted since it was new? When I rebuilt my Hardinge HLV (no -H) some of the holes in the apron gearbox and its cover were 1 thou undersize on 1/2" holes. I didn't realize untill some of the accuratey made replacement shafts wouldn't go into the needle roller bearings. I got around that by cylindrically grinding the shafts to fit.

I was about to post something similar to what eKretz said when I saw he already had. Steel is compressible and expandable, otherwise we could not use interference fits at all. If you squeeze a bearing down several thousandths, you have taken up all the internal clearance and you will have a tight bearing. As he often is, he is right on target. A very good machinery maker I knew would never fit a bearing with more than a couple of tenths interference.

Bill

Were the bearings of Chinese origin? I did a prototype job several years ago where all the parts, including the bearings, were made in China. I wound up scrapping all the bearings. They had excessive internal clearance and rumbled when you spun them.

Been there - done that!

It's been more than 15 to 18 years since I replaced those bearings on my Roll-In. But, I do recall that we used heat! At the time we contacted the company that bought Roll-In (seems like it was Kalamazoo), and they provided a procedure for installing the bearings.
I have no idea who owns the company now... If anyone has any information, I would certainly be interested in hearing from you.