# How do you replace the bearings in a motor?



## HMF

What is the procedure for replacing bearings on an electric motor, say a Baldor 1/2 HP grinder motor?

I have watched this video, and read this: http://www.craftkb.com/Uwe/Forum.aspx/metalworking/6265/Electric-motor-bearings

[video=youtube;I6y7tSPvmf8]http://www.youtube.com/watch?v=I6y7tSPvmf8[/video]

What type and where do I get the bearings?

Thanks,

Nelson


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## wawoodman

Nelson, 
I just googled "bearing shop queens NY" and got 3 hits. Once you get the old bearings out, just take them to the nearest shop. Generally, bearings are pretty reasonable.

A puller and a press will be your friends.


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## Starlight Tools

Nelson

Bearings are relatively easy to get ahold of. I keep dozens in staock and so would any small motor or other repair shop. Also there are industrial bearing houses and many car type parts stores.

Bearing removal, I have dozens of different bearing pullers and press fixtures just to facilite that. My Arbour press is what I will use most of the time. Supported by bearing knives like shown in the front page of that youtube video. If the rotor is too large in diameter to fit the arbour press, then it is either the big H-Frame Hydraulic press or a two or three arm puller, or a strong back puller like shown on the youtube picture. Bench grinders can be a bit tricky in that the shaft is really long for bearing pullers.

Walter


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## Starlight Tools

Also 

Bearing heaters are pretty rare beasts, very few home shops will have them.

When ever possible, and unless you have grease fittings on the motor, err for 2RS bearings with the two rubber seals. Open and shielded bearings let too much crap into the bearing in typical applications

Walter


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## HMF

starlight_tools link=topic=1628.msg9742#msg9742 date=1302501598 said:
			
		

> Nelson
> 
> Bearings are relatively easy to get ahold of. I keep dozens in staock and so would any small motor or other repair shop. Also there are industrial bearing houses and many car type parts stores.<BR><BR>Bearing removal, I have dozens of different bearing pullers and press fixtures just to facilite that. My Arbour press is what I will use most of the time. Supported by bearing knives like shown in the front page of that youtube video. If the rotor is too large in diameter to fit the arbour press, then it is either the big H-Frame Hydraulic press or a two or three arm puller, or a strong back puller like shown on the youtube picture. Bench grinders can be a bit tricky in that the shaft is really long for bearing pullers.
> 
> Walter



Walter,

I understand how a puller like the 2-jaw puller in the video is used, but I'm lost on how the arbour press works to separate the bearing and properly replace the new one. Perhaps a photo?
Thanks,

Nelson


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## HMF

*Can someone identify these pullers?*

So many pullers needed to do bearings. Can someone identify the ones in these photos please?  ::headscratch::

Thanks!!


Nelson


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## Fishchips

The first pic pullers are for bearings close to the end of the shaft, the other for a bearing deep on a crankshaft ie air compressor crank. I use a coiled single element hotplate for installing bearings.


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## StonewellMark

I just re-wired (some dumbass previous owner cut the wires just outside the motor housing), and replace the bearings in my rockwell tool grinder.  The bearings are easy to come by, just get the part number off the old ones, find a set of Timkens.  What a pain to re-assemble, I kept deforming the starter spring "plate" and the grinder wouldn't start, just hum.  Then I got "smart" and used an ohm meter during re-assembly walla a working motor.  As far as pullers I just used a cheapo 2 jaw puller.  Best of luck.

  Mark


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## Terry Lingle

a bearing heater is as simple as a 60 or 100 watt light bulb  in a stable socket  just balance the bearing on the bulb  and flip the switch  after 5 min or so flip it over ( the actual time is bearing and bulb dependent)  but the objective is even  heat on the inner race. I try for about 220 Deg F  or spit sizzles temperatures . 
A clean journal and a light wipe with never seize.  with a little practice  the bearing should slide into place with firm hand pressure ( wear gloves )


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## gonzo

On some of the larger motors the end bells have to go back on the end they came off of and the orientation kept the same as before. The best way is to punch a set of dots on adjacent surfaces before disassembly.
Sometimes when this is not done the shaft will lock up upon reassembly.
This is mostly a problem on larger motors with cast iron bells. However it's good not to take a chance.


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## Silverbullet

The puller set up in the second picture will do what you need , use the smallest separator then bolts to your puller. It won't hurt to use a bit of kroil on the shaft as you pull it. Bearings can bought lots of places Grainger , McMaster Carr , eBay . They are usually sealed bearings so most any of the shielded type in your size will work. Heating bearing may not be necessary , many times I find it easier to freeze the shaft overnight in a freezer . Usually the bearings drop on with light pressure. Then it's just putting it back together. Try not to rub any of the finish off the wound wires. Any dirt use a soft brush lightly clean what you can. If you have a brush run motor take care getting those in.


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## Firestopper

When it comes to pulling bearings, one single tool will not work every time.  The good news, many folks who have a decently equipped shop can modify generic pullers to get the job done correctly. The ability to machine and weld will save you time and money. Using tricks such as freezing and heating also go a long way. Pressing in new bearings is IMO far easier than pulling old ones. That said, I have found using a die grinder equipped with a thin cutoff wheel to score an old bearing race (on the shaft) in two or three places followed by a few light strike will result in success in removing. Obvious precautions taken to protect unwanted contamination while grinding. Over time this has become a less frequent operation as the collection of home made tool, shims etc are kept for the next bearing job that might come up, but always an option.

As far as procedures on electric motors, I have only done a few  Makita 4" grinders and smaller 2 hp or less sealed motors. On motors that I can't find information on, I start of by marking both ends with an indexing line for later reassembly. Remove the long screws and tap the shaft end cap with a small brass or soft hammer.Once it begins to move, Its pulled evenly off. Then the rotor assembly is pulled straight out slowly keeping track of any shims, spring washers etc. The inside of the motor can be cleaned out using low pressure air and electronic spray cleaner (air usually works well enough).  Depending on bearing set back a pulley puller could do the job, but always soak the shaft with penetrating oil.
I recently replaced the bearings on a Rockwell/Delta finishing machine. This is how I proceeded.


I had room to use a generic pulley puller for both bearings. This type of puller will damage the bearing being pulled out but who cares, they're already shot.


Here you can see the indexing mark I mentioned on the rear end cap and housing as well as the shims and spring washers in the lower right. I should have mentioned the fan on the rear was removed prior to disassembly (snap ring).
The rotor assembly shown was in great shape for a 34 year old motor. The right end of the rotor is the rear and shows the centrifugal switch and was also inspected prior to installation of new bearings.


The pressing operation went smooth and an old sleeve was used for this. The custom sleeve was turned long ago for a different job and lives in a bucket along with other pieces next to the press. The sleeve should slide freely on the shaft (OD) and contact the inner race of the new bearing only. I froze the bearing in a Zip-loc bag for 40-60 minutes prior to pressing. The bearings also had a small shim for them to seat agents once pressed (most of them will) but make sure they do prior to pulling old bearings. If no shoulder is found, then careful measurements should be taken to ensure proper depth of new bearings.




Nothing fancy about the HF 20T press. Its the correct tooling that makes it work.
These quality bearings found on the shelf at a local bearing house. All the bearings on the machine where a shielded type except one. I replaced them all with Koyo sealed bearings to keep the grit out. These new motor bearings ran under $5 each so check your local sources. On the upper left, you can see the sleeve that was used to press the new bearings in.


The inside of the motor after using low pressure air (40 psi) to clean out. Looks amazing considering its age.


Reassembly of the rotor;
You must be carful not to contact the rotor to the stator and line up the bearings to the end caps with all the correct shims in place. I was lucky to have an extra set of hands for this. The end caps have bearing bosses that retain said shims. A light coat of dielectric grease helps keep them in place during assembly. Once you verified everything is lined up properly you can begin to tighten the long screws evenly in a criss-cross pattern pausing to gently tap around the end cap using a mallet or small dead blow until fully seated and spinning the shaft by hand (during the process) to ensure all is well. Reinstall rear fan and vented cover and bench test if you feel the need. We installed the motor and then tested. It runs like a new motor without the grumbling it once had. I also replaced the start capacitor for good measure.



I hope this answers some questions and can be of help. 

Turn and burn,
Paco


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## markba633csi

Looking at all those pullers reminds me of all the tools I still don't have 
Mark S.


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## talvare

Nels,
There's a lot of good information given here for you. One thing I didn't see mentioned is the importance of how the new bearings are driven or pressed into place. If the new bearing is being pressed or driven onto a shaft, drive ONLY on the inner bearing race. If a new bearing is being installed into the end bell (usually not the case) or a bearing housing, drive ONLY on the outer bearing race. For removal of the old bearings it doesn't make any difference as they are being disposed of.

Ted


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## Firestopper

firestopper said:


> The sleeve should slide freely on the shaft (OD) and contact the inner race of the new bearing only





talvare said:


> Nels,
> There's a lot of good information given here for you. One thing I didn't see mentioned is the importance of how the new bearings are driven or pressed into place. If the new bearing is being pressed or driven onto a shaft, drive ONLY on the inner bearing race. If a new bearing is being installed into the end bell (usually not the case) or a bearing housing, drive ONLY on the outer bearing race. For removal of the old bearings it doesn't make any difference as they are being disposed of.
> 
> Ted


Mentioned in post. This is very important!


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## machPete99

You can probably use a piece of pipe to tap the new bearings in. Just make sure that it only hits on the inner race, as others have noted.


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## markba633csi

I've found that many standard pipe sizes make nearly perfect tooling for pressing metric size bearings like 6200 series for example. 
A 1.25" piece fits the outer race perfectly without hitting the shield.   Half inch piece for the inner race.
MS


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## tertiaryjim

When using a puller, put a protective cap over the end of the shaft so the center isn't damaged.
If the shaft has to be set up in the lathe, a bad center hole will make you crazy.


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## 4GSR

tertiaryjim said:


> When using a puller, put a protective cap over the end of the shaft so the center isn't damaged.
> If the shaft has to be set up in the lathe, a bad center hole will make you crazy.


Sometimes I'll take a hex nut like a 3/8 or 1/2 and put it between the center point of the puller and the end of the motor shaft to protect center in the end of the shaft.
I remember having to fix a center in the end of a motor shaft from a 75 HP DC motor before I could recut the commutator.   The lathe I was on did not have a way to install a drill chuck in the tail stock or anyway to hold a drill chuck in the tool post.  Had to grind a tool to go in and touch up and remove the dings at the front of the center.  I was doing this on a 36" Monarch lathe with a make shift adapted steady rest!


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## tertiaryjim

4gsr
A messed up shaft center was one of my pet peeves. Had to deal with a number of them.
Terry Lingle already mentioned  using a little never seize when installing bearings but I would like to add to that.
Too much never seize takes up space and can change the clearance of the bearing. It can also make a race seize to the shaft slightly crooked.
Small effects but they can cause problems or reduce bearing life.
Never seize applied too thick can also cause a bearing to score or gaule to the shaft on removal. Seen it!
I will put it only on the fit if the bearing is being heat shrunk.     Most small bearings have only two tenths interference.
If pressing the bearing on I will put it on the shaft and race but in all cases its spread so "thin" you can hardly tell there's anything there.


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