Electric motor bearings

Those are abec-1 bearings, typically. They are available inexpensively from most supply companies. I suspect you will have almost no trouble replacing them - you might punch-mark the end bell housings on the motor to get them back in the same orientation, don't ever press through the balls on new bearings (OK to do if you are removing scrap bearing though, with a puller) and if you want to keep using the grease fittings then don't put in sealed bearings.

Jim

I have a small motor with a bad bearing, and the motor is irreplaceable. Multi-speed, small size, exact fit reqd, part of a pair. Bearing is loose and noisy, it's a fan on my wood stove and I cannot get to it when the stove is hot.

My solution to date: I installed a tiny (ref capillary)tube to feed thick oil (STP) to the bad bearing. Just a drop works wonders. The oil would be too thick for good bearings but loose ones need thicker oil. I'm using a 25ACP case for an oil reservoir, filled with cotton. Has been working well so far. Note this is a horizontal shaft model, YMMV with a vertical shaft.

New bearings should be easy. Mark the bells. I'd use sealed bearings. Why did they fail? Even after a long time. Keep your wheels balanced and dressed. Check your flanges.

All good advice, but while I was in there, I'd fold over a piece of 280 sandpaper and do a good job of cleaning the contacts on the centrifugal switch if it's a cap. start motor. Blow everything out too.

Garrett Fulton

Well it's been in service here since 1987 so I'd imagine they are failing from normal wear. I have just rebuilt the machine ways with new linear shafting and bearings. No flanges per se as it uses plate mounted wheels. The bit of vibration is requiring more wheel dressing on some very friable open wheels. The machine grinds the knives from wood chippers and the like.

Can sealed bearings fit where the ones with grease fittings were?

Beecrofter asks: "Can sealed bearings fit where the ones with grease fittings were?"

Take this up with the friendly guy behind the counter of the local bearing supply store. Bearing vendors are probably the most knowledable of their trade among all the counter sales types. I am impressed every time I deal with one.

Bob Swinney

Dimensions are the same for open, sealed and shielded bearings. I would suggest shielded bearings unless you have a pretty severe contamination issue. Shielded are cheaper than sealed, more readily available and do a pretty good job of sealing out dust, dirt etc but does not work for water. Contact seals create drag and limits your speed (but probably is not a problem on 1800 rpm motor of this size). If you need a better seal than the shields provide NTN makes a non contact seal (add LLB to the basic bearing number) which provides better sealing than the shield but still does not contact the raceway. I'd also look for bearings lubricated with Exxon PolyRex EM grease - pretty much the new standard for electric motor manufacturers. Be sure to press the new bearings on the shaft using the inner race if you don't have a bearing heater to prevent brinnelling and shortening the life. Good luck - let us know if you have any further questions.

Iset my bearings on a 100w light bulb for a little while to expand them a little and warm the grease.

Why do you want to warm the grease??

If you do replace the open cage bearings with shielded or sealed, be sure to remove the grease fitting and plug the hole. It will not help any when someone 3 - 4 years down the road tries to lube the bearing and the grease has nowhere to go.

Nate

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Some shielded/sealed bearings are wider than the unsealed bearing, not many and usually in smaller or thin section bearings, but it's worth being aware. Also, the runout allowance and some of the dimensional tolerances are greater on shielded and sealed bearings than the unsealed version. I mention this since it sounds as though these bearings double as a grinding spindle.

Ned Simmons

Not necessary, I'm sure, but it redistributes the grease and makes sure it hasn't seperated. The first few minutes in a bearing's life are crutial.

I don't think you're accomplishing anything. You should never heat a bearing over 148 degrees C. to install (don't think you can get there with a light bulb) and the grease shouldn't flow until you reach approx. 170 (varies depending on grease). The grease is instantly redistributed as soon as the bearing rotates.

I'm old now and don't respond well to logic. This is the way I do it! I always face the bearing North when light bulb heating to make sure it alligns with North magnetic pole, allowing for deviation and compensation.

Now that makes sense! Gotta allow for the compensated deviates in this world! Gerry :-)} London, Canada

OK so this is what I have learned so far.

Electric motor bearings have so little load they should last a few lifetimes.

The original bearings probably fail because coolant either gets past the shaft or as the unit heats up and cools down vapor condenses inside and this causes lubrication failure or corrosion. Not too bad for 17 years of hard use.

Bring the old bearing with me to the distributer in case there are size differences. Don't push against anything but the inner ring. Use a lamp to preheat the bearing and try to get the newer lube.

Because the coolant kind of mists around I expect the next set to fail around 2021.

Now if I go with bearings that need grease through the zerk fittings whats a good policy for maintaining them, I know overlube kills more things than underlube cause I've done it on other things.

But don't forget to spin it on the bulb after heating to de-magnatize it - otherwise you may attract contaminates and they'll be sucked in as it cools. :-)

You're exactly right about overlube. Exxon/Mobil has done some research and has actually measured the amount of grease dispensed by individual grease guns and determined lube schedules based on that. It only amounts to a shot or two every 6 months or so (depending on application. I'll try to find the info for you. Another strange thought is to use a single shield bearing and mount it with the shield toward the lube source - actually acts as a metering device to help prevent overlube.

Push on the inner race if pressing onto the shaft. Push on the outer race if pressing into the housing.

i.e. Don't squash the bearing's balls. You know what it feels like, so have pity on the poor bearing :-)

Mark Rand RTFM