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Forum topic by bondogaposis posted 07-21-2013 06:52 PM 1388 views 0 times favorited 18 replies Add to Favorites Watch
View bondogaposis's profile


4754 posts in 2373 days

07-21-2013 06:52 PM

Topic tags/keywords: question

For those of you that have some experience repairing electric motors, how hard is it? I have an old Rockwell motor from my old lathe, probably ‘70s vintage. It still runs but get very hot after a short session and is starting to make growling noises as well. I assume I need to replace the brushes and bearings. Where do you get the parts? Will fixing it be worth it or might I be better off buying a new motor? I’ve never torn into a motor like this so I’m somewhat intimidated.

-- Bondo Gaposis

18 replies so far

View MrRon's profile


4793 posts in 3265 days

#1 posted 07-21-2013 07:05 PM

If the motor has brushes, then it is a universal motor. Motors of this type run at high speed and not as robust as an induction motor. You can find parts at www.ereplacement If you can find the right parts, it may be worth your time to try and fix it. I wouldn’t put too much money into a universal motor.

View Fred Hargis's profile

Fred Hargis

4996 posts in 2515 days

#2 posted 07-21-2013 07:23 PM

That’s almost certainly an induction motor (no brushes), and the way I would look at it is if I try to repair it and can’t, then I’d get a new motor. I suspect it won’t be that hard, but it can be aggravating. If that does happen to be a universal motor…consider getting a replacement that’s not. I agree with Ron, don’t put a lot of money into a universal.

-- Our village hasn't lost it's idiot, he was elected to congress.

View sprucegum's profile


324 posts in 2019 days

#3 posted 07-21-2013 07:35 PM

I have done some tinkering on my own motors but if you can find a motor repair shop local it may not cost too much and they usually have parts on hand to fix most motors. If there are any factories in the area that use a lot of motors ask the people that work there where they get their motors fixed. I have bought bearings before at the local auto parts store, if the bearing has a number on it chances are they can get it for you.

-- A tube of calk and a gallon of paint will make a carpenter what he ain't

View kdc68's profile


2657 posts in 2299 days

#4 posted 07-21-2013 07:38 PM

From readings of posts of TopamaxSurvivor, IMO he would be of great help in this situation. Maybe you can send him a pm…

Example of his electrical motor knowledge

-- Measure "at least" twice and cut once

View Mainiac Matt 's profile

Mainiac Matt

8082 posts in 2350 days

#5 posted 07-21-2013 08:03 PM

1. Carefully disassemble…it helps to take pics so you remember how it goes back together ( it may be a while)

2. Clean it out as best as you can…. Hi pressure air is your friend ( be sure to ware eye protection)

3. Spin bearings by hand… They should turn smoothely, with now crunchy feel or gritty noise, and no wiggle.

4. If the bearings are questionable, measure the inner dia, the outer dia. and the thickness (all in mm), then go to an after-market bearing store on line ( like XTP ) and go through the different styles of bearings until you find the one that looks like yours. Punch in your size, and order a spare, just in case you bung one up during installation. You should expect to spend $5 (or less) each, and as is often he case, S&H may cost more than the bearings…. Which is why you order an extra one right off.

5. There are lots of videos on You Tube that can guide you through the process.

6. Single phase induction motors have to have a starting capacitor, which is usually in a “bump” cover. The thing is, that if the starting cap is shot, the motor won’t start. But the cap may make a humming noise as it approaches failure. You can replace any cap with one of the same rating (in Farads) and size.

7. If OEM parts are available, they will cost a fortune.

8. The next failure is a breakdown of the insulation on the wiring. You can rewind a motor, though I wouldn’t suggest trying it yourself. If you have a local electrical motor shop, my guess is that it would run you about $90 to $125 to have them completely rebuild the motor, which should include all of the items listed above.

9. Induction motors can last very long time… especially when exposed to hobby shop levels of use.

Good luck with getting your motor figured out

-- It’s the knowledge in your head, skill in your hands and motivation to create in you heart that makes you a woodworker. - Mainiac Matt

View bbc557ci's profile


595 posts in 2096 days

#6 posted 07-21-2013 08:11 PM

FWIW… I have a 113 Craftsman table saw and the 1hp motor was acting up. I took it to a local electric motor rebuild shop and they wanted something like $60.00 just to look at it. The guy wouldn’t even speculate as to the cost of a rebuild, but said it could be as much as or even more than $150.00. I asked how much for a new one, and if I remember right it was $259.00. Well, I paid $35.00 for the TS so I wasn’t gonna sink that kind of $$ into a motor.

So…I put a “looking for” add add on Craigslist, and about a week later a guy emailed me saying he had an almost new GE capacitor start 1hp motor that he’d sell for $45.00. Needless to say I grabbed it. Moral of the story is…. check around and you might come up with a good deal.

-- Bill, central where near the "big apple"

View bbc557ci's profile


595 posts in 2096 days

#7 posted 07-21-2013 08:15 PM

I didn’t see your post Matt, didn’t mean to discourage a DIY rebuild.

-- Bill, central where near the "big apple"

View Loren's profile


10476 posts in 3670 days

#8 posted 07-21-2013 08:34 PM

A 1/2 hp induction motor isn’t worth a lot.

I would replace it. Used fractional horsepower motors
are easy to find and cheap.

View MrUnix's profile


6757 posts in 2221 days

#9 posted 07-21-2013 08:37 PM

That is a capacitor start induction motor manufactured by Marathon Electric (no brushes). Based on the symptoms, you will need to open it up to see what is going on.. I could just be full of cobwebs and sawdust, or more likely, the bearings are starting to go. Fortunately, it’s really easy to do and you don’t need any special tools. There are just four nuts/bolts holding the ends on.. make sure you make some kind of marks so you can align the end pieces back in the same place when putting it back together. Once you get it apart, you can determine if it was just dirty or if new bearings are required. Actually, at that point I would probably just go ahead and give things a good cleaning and replace the bearings anyway. Bearings will be some standard size that you can get for a couple of bucks at your local bearing supplier or online at places like Accurate Bearing.


-- Brad in FL - In Dog I trust... everything else is questionable

View 8iowa's profile


1580 posts in 3783 days

#10 posted 07-21-2013 08:52 PM

It appears to be a reversible single phase 1/2 HP motor, 1800 rpm. There are no brushes. If you take the end caps off you will see a centrifugal switch that “turns off” the starting winding once the motor gets up to speed. These switches often get caked up with dirt and sawdust, which you can clean up.

While you have the rotor assembly out, take it to a shop to replace the bearings, or perhaps you can do this yourself. I suspect that these are sealed bearings.

-- "Heaven is North of the Bridge"

View RussellAP's profile


3104 posts in 2308 days

#11 posted 07-21-2013 08:55 PM

Those old motors are under rated. I’d take it apart and clean it real good. Probably all it needs. WD40 is good to clean it with, but be sure to get it all off, it collects dust and laps out bearings.

-- A positive attitude will take you much further than positive thinking ever will.

View bondogaposis's profile


4754 posts in 2373 days

#12 posted 07-21-2013 09:42 PM

This what I got so far. The bearings are definitely feeling crunchy bad. How do I get them off?

-- Bondo Gaposis

View Grandpa's profile


3259 posts in 2697 days

#13 posted 07-21-2013 09:48 PM

Use a puller. The correct puller will be cheaper than a new motor. I have been there to so don’t ask.

View MrUnix's profile


6757 posts in 2221 days

#14 posted 07-21-2013 10:07 PM

Pullers will make your life easier, but not required. I’ve used large screwdrivers to pry them off, front end ball joint ‘pickle forks’ work well also. Many times, you can support the rotor by the bearing and drive the shaft down through the bearing with a wooden mallet (or using a press). Last resort is to take a hack-saw and cut the outer race off, remove the innards (ball bearings and cage) and then lightly cut the inner race until you can pull it off. However you do it, just take care not to score, cut or bang the shaft. While you have it open, use compressed air to blow out any gunk in the stator windings and housing, give the centrifugal switch a couple drops of oil, clean everything else up and generally look around to make sure nothing else is amiss (such as frayed wiring, evidence of abnormal wear, etc..).

That motor looks to be in pretty good shape.. once you replace the bearings, it should be good for another 30+ years :-)


-- Brad in FL - In Dog I trust... everything else is questionable

View shampeon's profile


1775 posts in 2205 days

#15 posted 07-21-2013 10:11 PM

The cheapie bearing puller set from Harbor Freight is actually a decent tool, and has paid for itself in pulling spindles, bearings, and races off my old woodworking machines. All the rods, bolts, and nuts are standard so you can make extensions and jigs to get oddly shaped things pulled apart.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

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