# Replacing Motor Bearings



## erics37 (May 7, 2009)

Jlarson said:


> I'm I like the only electrician left who does mechanical work on motors and pumps or something? :blink:


I don't even know where to start on tearing apart a motor  My apprenticeship curriculum spent a total of several weeks teaching me about the history of the IBEW and stuff but none of the motor texts did anything more than describe the components that make a motor work.

I never had any on-the-job training on motor repair either, because no one at my shop knows how to do it.

The good news is that there's a small motor shop right behind my house. Literally I could probably pee on the side of their building from my backyard if I had enough soda pop to drink. I haul motors down there occassionally and I've been picking the shop owner's brain for info every time I go there :thumbup:


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## micromind (Aug 11, 2007)

I can't even think of how many bearings I've replaced over the years, but it's been a lot!

Start switches and capacitors in single phase motors too. 

Seriously, replacing bearings in your average everyday electric motor is so simple, and they're readily available as well. 

A lot of motors these days even state the type of bearing on the nameplate. 

Rob


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## erics37 (May 7, 2009)

micromind said:


> I can't even think of how many bearings I've replaced over the years, but it's been a lot!
> 
> Start switches and capacitors in single phase motors too.
> 
> ...


I've got an old single phase 10 hp motor sitting at the shop. I think I'm going to bring it home and rip it apart just to see what's in there. I know the capacitor is shot but maybe it will be a good learning experience for me.


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## Jlarson (Jun 28, 2009)

micromind said:


> Seriously, replacing bearings in your average everyday electric motor is so simple, and they're readily available as well.



Exactly, some people act like only a motor shop can do it. These are also the people that complain when the shop then tells them it needs to be rewound too .


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## John (Jan 22, 2007)

micromind said:


> I can't even think of how many bearings I've replaced over the years, but it's been a lot!
> 
> Start switches and capacitors in single phase motors too.
> 
> ...


Same with me. Sometimes it is easier to replace the motor bearings right in place. you don't have to unwire the motor and sometimes don't even need to unmount it.

Most motor bearings are metric. A 6203 bearing has an inside dia of 17 mm, an outside dia. of 40 mm and a width 12 mm.
Pump motors have metric and inch inside dia. bearings. Motor backside bearing inside dia. is metric and shaft side bearing inside dia. is inch.

Years ago I used to to motor gearbox repairs....if you have the parts. Worked in a pencil factory in Calif. and would do 1-4 motors and/or gearboxes a shift. :whistling2:


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## Mike in Canada (Jun 27, 2010)

Jlarson said:


> Or actually any motor part for that matter, who does it? I mean themselves not sending it out to a motor shop.
> 
> The other day I ripped apart a 2 hp TEAO that was squealing to see if it's bearing were shot and needed to be replaced. Everyone looked at me like I was nuts for taking the thing apart.
> 
> I'm I like the only electrician left who does mechanical work on motors and pumps or something? :blink:


 I always take bad motors apart. Even if the bearings are good, a good, hard look at the stator can give you a very good idea of what happened to them. I do replace motor bearings, myself. However, I should mention that I'm also a licensed millwright.


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## McClary’s Electrical (Feb 21, 2009)

I always repair bearings, capacitors, overloads, and centrifugal switches my self. More than that goes to the motor shop


I got the same look from a maintenance guy in International Paper. They wanted to junk a motor because it needed (1) bearing. About 30 bucks to get it going. I ripped it apart, pulled the bearing off the shaft and handed it to him inside of 5 minutes. They employ parts swappers


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## lefleuron (May 22, 2010)

We do as much with motors as we can, bearings, caps,etc. The only thing that limits us is size, and actual problem.

If you have a 250 HP motor that makes no bearing noise, but the shaft itself gets really, really hot- that's beyond our reach. 

But we do have a growler, some pullers, a press, etc. and can handle the simple fixes.


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## Greg (Aug 1, 2007)

I haven't replaced bearings in years but in the Navy we replaced bearing on a regular basis. I can still do it in my sleep. If it (motor) needed rewinding then it was removed from the ship and sent S.I.M.A. on base on rewound. Rewind school was one school I never got the chance to go to. It would have been interesting.


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## electricmanscott (Feb 11, 2010)

You guys are so cool. 

Not everybody knows how to replace bearings. I do, some of you do, but is that any reason to look down your nose at somebody that doesn't?


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## BBQ (Nov 16, 2010)

Jlarson said:


> Or actually any motor part for that matter, who does it? I mean themselves not sending it out to a motor shop.
> 
> The other day I ripped apart a 2 hp TEAO that was squealing to see if it's bearing were shot and needed to be replaced. Everyone looked at me like I was nuts for taking the thing apart.
> 
> I'm I like the only electrician left who does mechanical work on motors and pumps or something? :blink:


During my 5 years as a 'carny' we fixed anything that would break, from trash trucks to DC drives.

Motor bearings we often did with the motor still in place with a line waiting for the ride to open. The real fun was working on hydraulic pumps / systems that just minutes earlier had been running for 8 or 10 hours, hot hyrdo oil is not a lot of fun. I had my work boot pretty much filled to the brim with hot oil, I could not get my boot off fast enough.


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## leland (Dec 28, 2007)

Out for repair- other things to concentrate on.
Would be a good thing to dabble with,so when your older and drop the tools you got something to do in the basement to supplement the income.

If it is critical equipment- out and replaced-repair the old and put in stock.

most of my motor repairs are only 1-$300 bucks, and the repairs are usually only around $$40 - $125.- so most customers will go with the back up motor scenario.


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## Mr Rewire (Jan 15, 2011)

Alot depends on the motor size and location on small motors its more cost effective to replace it than for them to pay my labor to rebuild it often the customer will send the old motor to be refurbished and then keep it on hand to replace others.The big 100Horse motor at the feed mill I will take it apart.


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## BBQ (Nov 16, 2010)

Mr Rewire said:


> Alot depends on the motor size and location on small motors its more cost effective to replace it than for them to pay my labor to rebuild it


I thought the question was about swapping a bearing, not a re-build.

On a small motor I can swap in a new bearing pretty quickly and small bearings are cheap.


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## Mr Rewire (Jan 15, 2011)

BBQ said:


> I thought the question was about swapping a bearing, not a re-build.
> 
> On a small motor I can swap in a new bearing pretty quickly and small bearings are cheap.


 Most of the time I don't have the bearings and niether does the customer but they will have a spare small motor.


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## backstay (Feb 3, 2011)

Other reasons to repair instead of replace would be obsolete motors that would be impossible to replace without modification of the mounting or coupling.


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## guest (Feb 21, 2009)

electricmanscott said:


> You guys are so cool.
> 
> Not everybody knows how to replace bearings. I do, some of you do, but is that any reason to look down your nose at somebody that doesn't?


What's with the attitude? No one here is "looking down their noses" at anyone. The OP was wondering simply if he's the only one who does motor repairs. 



backstay said:


> Other reasons to repair instead of replace would be obsolete motors that would be impossible to replace without modification of the mounting or coupling.


I had to engineer a new bedplate for a 5hp blower motor on Catalina Island, it was the exhaust fan for the film projectors, one of the oldies with a big flat leather belt and the motor mounted about 8 feet away from the fan. 

The old 1930's Westinghouse motor let out the magic smoke due to a few things: loose connection in the peckerhead and bypassed overload heaters. And it was the most foul smelling burnout I had ever encountered. 

The new motor got a brand-new fused local disconnect, and a new contactor/ol relay with phase loss detection. 

I wish I had taken pics, it was nice when it was done.


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## Rudeboy (Oct 6, 2009)

_Awww, come on guys, it's so simple maybe you need a refresher course. [leans arm on hot engine part, then jumps away] Heyya! It's all ball bearings nowadays. Now you prepare that Fetzer valve with some 3-in-1 oil and some gauze pads, and I'm gonna need 'bout ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State._
:thumbsup:


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## miller_elex (Jan 25, 2008)

Greg said:


> I haven't replaced bearings in years but in the Navy we replaced bearing on a regular basis.


Yeah, in the navy we would rip anything apart and rebuild it.

There is a supply house in your town that sells just bearings. I remember alot of SKF's. The bearing catalog (before internet,) had tables on how to spec bearings, and they'd also take the part number off the existing bearing and cross-ref it to a new one.

You've got to use a mechanical puller to get it off the shaft, and soak the new one in a hot-oil bath (think deep-fryer,) to get it on. Some mechanics used liquid nitrogen to shrink parts, but I've never done it. Heard about one guy who mistakenly put liquid oxygen on a part and it blew him to Kingdom come.


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## BBQ (Nov 16, 2010)

miller_elex said:


> You've got to use a mechanical puller to get it off the shaft, and soak the new one in a hot-oil bath (think deep-fryer,) to get it on. Some mechanics used liquid nitrogen to shrink parts, but I've never done it. Heard about one guy who mistakenly put liquid oxygen on a part and it blew him to Kingdom come.


I put a rebuilt 200 HP in a walk-in freezer overnight and put the steel coupler in our shops lunch oven for a while. It slid on easily, it had taken a 50 ton puller and some heavy beating to get the coupler off of it originally.


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## Jefro (Jul 28, 2009)

Why, just the other day, I...


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## oldtimer (Jun 10, 2010)

Jefro said:


> Why, just the other day, I...




O M G, you welded the bearing on? :laughing:


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## Jlarson (Jun 28, 2009)

electricmanscott said:


> Not everybody knows how to replace bearings. I do, some of you do, but is that any reason to look down your nose at somebody that doesn't?


 I'm not looking down on anyone neither is anyone else. 




erics37 said:


> I've got an old single phase 10 hp motor sitting at the shop. I think I'm going to bring it home and rip it apart just to see what's in there. I know the capacitor is shot but maybe it will be a good learning experience for me.


Go for it, ripping stuff apart and learning from it is fun.


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## Jefro (Jul 28, 2009)

miller_elex said:


> You've got to use a mechanical puller to get it off the shaft, and soak the new one in a hot-oil bath (think deep-fryer,) to get it on. Some mechanics used liquid nitrogen to shrink parts, but I've never done it. Heard about one guy who mistakenly put liquid oxygen on a part and it blew him to Kingdom come.


I have one of those deep fryers in my shop. If you know your way around a gear puller, that'll get you squared away more often than not. Also, Aqua-Lube is a great product. You can use it on anything, it wont eat up rubber parts like petroleum-based grease will.:thumbsup:


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## Jefro (Jul 28, 2009)

oldtimer said:


> O M G, you welded the bearing on? :laughing:



Haha, someone was trying to make it stick to the shaft with grease!

Actually someone had been greasing a sealed bearing on a 40hp house pump motor and it was making an unpleasant angry sound...


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## eric7379 (Jan 5, 2010)

I always tear motors apart and replace the bearings in them. Of course, it all depends on the type of motor that it is. If it is a low-cost motor and I know that the windings are good but the bearings are shot, it goes in the trash. A lot of the motors that we use are OEM-only and can cost 2-3 thousand for a 3 HP motor. 

Every once in a while, we come across a motor in which the keyway is shot or the shaft is bent. If we have the time to do it, we turn down the shaft until it is true and then sleeve it. 

I've also ran across a few cases in which we had a PM DC motor that was showing that the armature was shorted to the frame. Took it apart, cleaned the hell out of the armature with contact cleaner to get all of the carbon dust off of it, put it back together and it worked like new. Of course, I also replaced the bearings while I had it apart.


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## Zog (Apr 15, 2009)

I don't see why not, as mentioned on smaller motors they are easy to replace and easy to find. We replace them on breakers every day.


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## John Valdes (May 17, 2007)

Jlarson said:


> Exactly, some people act like only a motor shop can do it. These are also the people that complain when the shop then tells them it needs to be rewound too .


Before you install the new bearings, do you measure the tolerances? Machine check the tolerances? Good motor shops do. If you cannot trust your motor shop, you should find one you can.




Jefro said:


> Haha, someone was trying to make it stick to the shaft with grease!
> 
> Actually someone had been greasing a sealed bearing on a 40hp house pump motor and it was making an unpleasant angry sound...


Greasing motor bearings can be an issue. Less is better than more. But the most important thing to remember when greasing bearings is to use the correct grease. Do you contact the manufacturer for grease recommendations? Do you know what type and how much to use? Some greases are not compatible and the addition of a non-compatible grease could cause immediate failure.



Zog said:


> I don't see why not, as mentioned on smaller motors they are easy to replace and easy to find. We replace them on breakers every day.


If the customer must run and you have the bearing, go for it. Unfortunately changing bearings is the easiest part. Its the possible machine work that will make or break this mechanical repair.
Just changing bearings may get you through a rough spot. But if you do not know what is expected and required to change bearings, you are not doing anything but teaching others to do shoddy work.

You know this better than anyone on this forum from my vantage point. You know how important a good machinist is to the mechanical aspect and proper repair of any electrical apparatus.


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## MDShunk (Jan 7, 2007)

I'll stick bearings, caps, and end switches in small motors less than 5hp, but send anything bigger than 5hp to the motor shop. I'm not going to mess around with a larger motor (read- higher dollar), guessing that all it might need is a couple bearings. On Satruday, I was faced with a motor at a dairy that probably needed two bearings, but I took it to the motor shop. It was only a 10hp, but the catalog price on that motor was $5,600. I'm not messing with that to try to save a guy a couple bucks.


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## Jefro (Jul 28, 2009)

John Valdes said:


> Greasing motor bearings can be an issue. Less is better than more. But the most important thing to remember when greasing bearings is to use the correct grease. Do you contact the manufacturer for grease recommendations? Do you know what type and how much to use? Some greases are not compatible and the addition of a non-compatible grease could cause immediate failure.


Yeah, all that stuff, and these bearings were sealed.


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## Mike in Canada (Jun 27, 2010)

> Greasing motor bearings can be an issue. Less is better than more. But the most important thing to remember when greasing bearings is to use the correct grease. Do you contact the manufacturer for grease recommendations? Do you know what type and how much to use? Some greases are not compatible and the addition of a non-compatible grease could cause immediate failure.


 Greasing motor bearings can be a HUGE issue. You can buy "EMB" from many if not most grease manufacturers - Electric Motor Bearing grease. All it is is grease that does NOT have the EP additives that are incompatible with motor windings.
Beyond using the correct grease the biggest problem is over-greasing. Many plants have a "Johnny Grease-Gun" running around causing all kinds of mayhem. I have long said that a grease-gun is a lethal weapon in the hands of the inexperienced.
I reached the point that I stopped greasing motors altogether UNLESS they were of sufficient size that they had a flow-through design with bleeders and the whole nine yards. In those cases I would grease, but it's a long, drawn-out procedure because you have to verify that the bleeder isn't clogged, and it's an exacting thing. If you over-grease the bearings, the extra grease WILL go into the motor and coat the windings. Even if it's the 'right kind' of grease it's still a bad thing.


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## BBQ (Nov 16, 2010)

John Valdes said:


> Before you install the new bearings, do you measure the tolerances? Machine check the tolerances? Good motor shops do. If you cannot trust your motor shop, you should find one you can.
> 
> 
> 
> ...


It's just a frikking electric motor, it ain't rocket science.

Jesus :laughing::laughing:


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## frenchelectrican (Mar 15, 2007)

I do replace the bearing from time to time but I always check the motour shaft for straightness { run true } few case I have to return it quick or restraight it out { if bearing got serious overheated or fubered then junk it }

But few special class motor then I will send it to the motour shop they will able deal with it in better way.

Merci.
Marc


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