What actually happens when you don't change bad bearings?

catalytic · Jun 24, 2017

For the decade or so that I've been maintaining my own machines, I'm a stickler for replacing bearings whenever they sound bad, feel bad, or feel dry/soapy. I do this mostly because I have heard and read here that horrible things may happen if I don't.

Aside from a bit of heat or runout, what are these horrible things, and what happens if you continue to run an old soapy bearing? If a bearing sounds bad but there is no perceptible heat/runout, is there any urgency to change it?

Do they apply equally to basic radial motor bearings and to quality spindle bearings (angular contact)?

*EDIT* after looking at the first few replies, I should specify I'm mostly interested in:
1. radial ball bearings in fractional to 5hp motors that you find on the various machines around your machine shop and
2. angular contact spindle bearings such as the ones in your bridgeport and toolroom lathe

Has anyone actually seen a bearing lock up and the shaft or housing spin in either of these cases? If so, is are there a lot of warning signs first?

DDoug · Jun 24, 2017

Loaded question, machine specifics please.

alonzo83 · Jun 24, 2017

I wished I was as good at judging bearings as the op.

moonlight machine · Jun 24, 2017

catalytic said:
For the decade or so that I've been maintaining my own machines, I'm a stickler for replacing bearings whenever they sound bad, feel bad, or feel dry/soapy. I do this mostly because I have heard and read here that horrible things may happen if I don't.

Aside from a bit of heat or runout, what are these horrible things, and what happens if you continue to run an old soapy bearing? If a bearing sounds bad but there is no perceptible heat/runout, is there any urgency to change it?

Do they apply equally to basic radial motor bearings and to quality spindle bearings (angular contact)?

What is a soapy bearing? I have repaired plenty of bearing housings and shafts that were damaged by bearings that were run to destruction, it can get pretty ugly. Run a motor bearing too long and the armature rubs on the field laminations. It depends where the bearing is, a spindle bearing on a lathe that rumbles will show in the finish on your work.

CarbideBob · Jun 24, 2017

Depends on what is going bad.
I have surface grinder spindles that have been making noise for 5+ years with no problems in size control or finish.
(Only real problem listening to the whine all day long)
Have had other bearings that made just a tiny bit of noise and everything went to poop.
Always best to replace at the first hint of not right, sometimes you......
Bob

Red James · Jun 24, 2017

Bad bearings tend to lock up and cause the inner bore to spin on the shaft, ruining the shaft. Sometimes the outer race spins in its bore and ruins that bore. Neither of these are good, usually requiring expensive repair.

rons · Jun 24, 2017

A shaft that has been spun upon by a bearing will have to be chrome plated and precision ground back to dimension. A typical problem that has to be fixed on BMW twin motorcycle cranks.

JS · Jun 24, 2017

When in doubt change your bearings...

I work in a mine so I'll say this much ........

Imagine the bearings in a $300K gearbox running dry and failing. Think 20K lb gearbox driven by a 1200hp motor and a shaft that locked up under full power 1800 rpm. The motor about 10K lbs was about 300 foot up a mountain literally broke bolts, structure and went over the edge of the platform and down the mountain. a 4" shaft was bent around 40 degrees. Bent 2" plate steel as it flew apart.... :leaving:

JST · Jun 24, 2017

There's bad, and there is stating to go bad.

Unless there is dirt in them, they do not wear out, they start to get pitted as small pieces fatigue and crack out of the surfaces of races and balls. That means they make noise.

Eventually they get rough, and may lock up due to larger chips spalling off.

"Soapy" is different, that's from separated grease, they get rough, but its usually a "soft" sort of roughness.

I bet that mine gearbox cost some serious cash, and time, to replace. Likely someone got fired.

Davis In SC · Jun 24, 2017

JS said:
When in doubt change your bearings...

I work in a mine so I'll say this much ........

Imagine the bearings in a $300K gearbox running dry and failing. Think 20K lb gearbox driven by a 1200hp motor and a shaft that locked up under full power 1800 rpm. The motor about 10K lbs was about 300 foot up a mountain literally broke bolts, structure and went over the edge of the platform and down the mountain. a 4" shaft was bent around 40 degrees. Bent 2" plate steel as it flew apart....

But on the other hand, I can live with a slightly gritty bearing in my fidget spinner... As other above stated, depends on the application...

Bill D · Jun 24, 2017

And when it goes bad on your Mars rover you have to park it and wait for the repair space ship to bring in the spare parts.
Bill D
BTW It will literally take an act of congress to send the parts.

Danny VanVoorn · Jun 24, 2017

Ask the guy with the 911 that had an IMS bearing go, better yet I'll tell you. It cost him thousands for a complete, new engine. Seems those high performance engines have low tolerance for bearing grit running through the lube system.
If its just a cheap, disposable big box store electric fan or some other consumer grade item run it until it quits. If it's something that is worth getting every pennies worth then best to stay on top of things.

CarbideBob · Jun 24, 2017

I don't own a Mars Rover just plain ole earth bound 1/2 million dollar machine tools.

kpotter · Jun 24, 2017

I have an old as dirt blanchard grinder that is so loud I wear hearing protection. The spindle bearing are shot. The machine is from the early 1920s I doubt I can find any bearing for it so I just run it and keep oil in it. The thing has been screaming for a couple of years now. It is no worse or better than the day I got it.

CarbideBob · Jun 24, 2017

kpotter said:
I have an old as dirt blanchard grinder that is so loud I wear hearing protection. The spindle bearing are shot. The machine is from the early 1920s I doubt I can find any bearing for it so I just run it and keep oil in it. The thing has been screaming for a couple of years now. It is no worse or better than the day I got it.

The bottom bearing is probably just a standard Timken roller but not cheap due to size. Most of my top are off the shelf ball style.
If you flush the bottom one with kerosene a few times filling, run a few minutes, drain/rinse/repeat.... it might quiet down a bunch.
(not that I would ever do such a thing to my Blanchards but sometimes the spindle just stops too fast and you gotta make parts....

)
Bob

Forrest Addy · Jun 25, 2017

Well, for one failing bearing don't heal up. Noticing signs of bearing failure should be the start of a maintenance project where the necessities (new bearing, seals, tools, lifting gear, etc) are located, purchased, gathered and at the first opportunity employed to replace the bearings.

I suggest a window of a month or two unless the bearings are actual screamers where attempts at interim lubrication has no effect. Then you better not dally. Should the bearings fail utterly, the shaft and endbell fits are sure to suffer making a repair/buy decision inescapable

All periodic jobs should be organized this way. When I was still active n my shop the holidays between Christmas and New Years was my opportunity to clean and calibrate mikes deep clean the machinery, execute reair projects, clean and organize the shop, change fluorescent tubes, list for future purchase materials and equipment inventory equipment, material, consumables. Well run commercial shops operate this way as in acknowledging recurring work to maintain thee facilities etc though it may be quite informal in two to ten man shops.

However the home shop owner would benefits by having some form of organization in place if only to keep up with stocks of abrasives and motors having failing bearings.

MattiJ · Jun 25, 2017

What I have seen and heard ball bearings are not so prone to FUBAR style failure as tapered/cylindrical roller bearings.
When the rolling elements in roller bearing decide that its time to turn sideways relative to rotation at full speed the results are magnificient. =Total lock-up, broken shafts, exploded bearing housings and worldwide nuclear war.

Tyrone Shoelaces · Jun 25, 2017

I was working at one place on a Sunday morning. I needed compressed air so I went to the compressor house to start the compressor up. Normally this job was done by a labourer who opened the place up. It was a few months since I'd been near the compressor.

When I started the compressor up the outboard bearing was making quite a racket. My pal and I decided to investigate the noise. The bearing housing was the split type were you could take the top half off. When we took the top off you could actually see right through the bearing where the balls and cage should be. The cage was more or less destroyed and all the balls had just gathered at the bottom of the bearing when the shaft stopped rotating. It must have been like that for a while.
We whipped the old bearing off and managed to get a new one that day even though it was a Sunday.

In my toolbox I still have half of a 1.25" ball out of another bearing, several of the balls were sheared completely in half !

Regards Tyrone.

Jim Williams · Jun 25, 2017

During the 1960s, we lived in a remote town in the western part of Virginia. We owned a 1960 VW Microbus which had a front wheel bearing go bad. When I examined the roller type bearing, it contained a lot of metal bits on both sides, and the rollers and races were severely pitted. Having only the one vehicle available, and needing it to go after parts, I cleaned the bearing with solvent and lubricated it with fresh bearing grease. After driving the bus. to Bluefield, WV, and back, I replaced the complete bearing with new parts. I was amazed to fing that the damaged bearing had "healed", and was turning without noise. The edges of the pits were smooth, and no debris had been generated. I suspect that the damaged bearing would have continued to work well for a long period. Ball and roller bearings can be inherently noisy, and continue to give good service. In many instances, a good cleaning and relubrication is all that is needed.

Jim

moonlight machine · Jun 25, 2017

Jim Williams said:
During the 1960s, we lived in a remote town in the western part of Virginia. We owned a 1960 VW Microbus which had a front wheel bearing go bad. When I examined the roller type bearing, it contained a lot of metal bits on both sides, and the rollers and races were severely pitted. Having only the one vehicle available, and needing it to go after parts, I cleaned the bearing with solvent and lubricated it with fresh bearing grease. After driving the bus. to Bluefield, WV, and back, I replaced the complete bearing with new parts. I was amazed to fing that the damaged bearing had "healed", and was turning without noise. The edges of the pits were smooth, and no debris had been generated. I suspect that the damaged bearing would have continued to work well for a long period. Ball and roller bearings can be inherently noisy, and continue to give good service. In many instances, a good cleaning and relubrication is all that is needed.

Jim

Strange that it had rollers, mine had ball bearings.......

What actually happens when you don't change bad bearings?

Cast Iron

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