Not sure how to upload a video but my lathe has what sounds to me like a failing motor bearing. The spindle turns freely by hand and the noise has been isolated to the motor by removing the drive belt and running the motor with no load. Does anyone bother to replace failed motor bearings or does it make more sense to replace the motor entirely? A replacement motor is not available as an OEM part so I would have to find a similar motor with the same frame, shaft diameter, etc., which might be as much trouble as replacing the bearings.
-
It's time to cast your vote in the April 2025 Turning Challenge. (click here for details) -
Congratulations to Steve Bonny for "A Book Holds What Time Lets Go" being selected as Turning of the Week for 28 April, 2025 (click here for details) -
Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.
Motor bearing failure
- Thread starter Holmes Anderson
- Start date
I have replaced ball bearings in several motors. Not too difficult if you are mechanically inclined. I just ordered bearings to replace on an old grinder. I think they were $7 for two.
The old ball bearings should have a 4 digit number stamped on them. Usually starts with 6. The rest of the numbers/letters are for the seals. For example the ones on my grinder were 6202-z, which has a metal dust shield on one side. The one I ordered is 6202-2rs, which has rubber seals both sides.
I would only go the new motor route if I had other problems when replacing the bearings. If you get stuck and can’t do it, you haven’t spent much $ to try.
If it has sleeve bearings, it’s much harder to find a replacement and you might need a bearing press.
The old ball bearings should have a 4 digit number stamped on them. Usually starts with 6. The rest of the numbers/letters are for the seals. For example the ones on my grinder were 6202-z, which has a metal dust shield on one side. The one I ordered is 6202-2rs, which has rubber seals both sides.
I would only go the new motor route if I had other problems when replacing the bearings. If you get stuck and can’t do it, you haven’t spent much $ to try.
If it has sleeve bearings, it’s much harder to find a replacement and you might need a bearing press.
It's pretty simple really, you just remove the motor and take it to an electric motor repair shop. They'll fix you right up.
Thank you both. I plan to take it to the local motor guy on Monday. The last time I had a motor failure I ended up paying $50 just to be told my motor was toast but I'm fairly sure this one can be repaired.
What if you don't have a local electric motor repair shop? Ski repair? You bet. Bike repair? No problemo. Industrial equipment? Huh?
john lucas
AAW Forum Expert
I just put new bearings in a Grinder. The bearing replacement was easy. Getting the housing back on took some paitience and a few 4 letter words.
Yeah, as another poster mentioned, what motor shop? Back in the day we had quite a few, all gone now except the shops who do high horsepower, really expensive motors. If the motor is three phase easy to replace bearings. Single phase, capacitor start motors have the centrifugal starting mechanism to be careful not to damage. DC motors have brushes to be careful of.
Get the number off the bearing. Some old bearings may be open shielded (not sealed). Back in the day seals available at the time caused frictional heating. Seals are much improved now so the bearing house can provide a bearing with seals appropriate for the bearing's running rpm.
When taking the motor apart mark end bells orientation with respect to the center section. Sometimes obvious, not always though.
With wages what they are I'd guess an inexpensive bearing plus labor would be at least a hundred bucks at a motor shop. I just replaced a couple bearings, but like most everything they cost about twice what my past experience told me to expect.
Years ago I had a motor shop tell me that if it's sized about 1.5hp or less, they don't repair, they replace. Their view was that the repair bill averaged the price of a new motor.
Now that we are in new economic times, where everything seems to be 2-3x, or more, its cost of a decade ago, maybe it does pay to repair these motors rather than replace.
Now that we are in new economic times, where everything seems to be 2-3x, or more, its cost of a decade ago, maybe it does pay to repair these motors rather than replace.
The motor seized on my Rikon bandsaw a month after I got it. Rikon sent me a replacement overnight and didn't require me to send back the old motor. I have considered getting it fixed, but I don't know what I'd do with it if I did.
The cost to professionally repair a motor is subject to the same inflation as the cost of the new motor therefore the only change in a decade is the value of a dollar.
What lathe is it? I have a powermatic that developed a high pitched squeal in the motor at higher rpm. It was ear splitting loud. Powermatic sent me a new motor no charge.
Years ago, the bearings on my 3520A went out. I was able to get new bearings and a new belt on it at a local repair shop for less than the parts would cost getting them from PM. That was 25 years ago though.
robo hippy
robo hippy
I will have to repair it for myself after all. The local motor repair shop wanted $125 just to prepare a quote that they told me would be for some amount greater than half the cost of a new motor. It took me less than 30 minutes to break down the motor to where the bearings are ready to be pulled. 2 HP 3 Ph Marathon motor "made in USA" with bearings made in China. Any recommendations for a bearing puller?
Dave Landers
Beta Tester
Last time I needed one, I went to the local NAPA auto parts store and they loaned me one.
Go to Harbor Freight and buy a puller , cheap and good for light duty work
If there is a bearing dealer in or near your town you could probably get better quality bearings and of course it would cost more, otherwise there are several sites online that you could order from.
If there is a Motion Industries near you you can purchase your bearings from them
I replaced the bearings on an old grinder yesterday. One slid off the shaft easily. For the other I supported the bearing in a vise and tapped the end of the shaft with a wooden mallet. Didn’t take much force. I do have a gear puller, but would have had to go looking for it.
The new bearings we tighter than the old so I had to press them on. I don’t have a bearing press but the lathe tail stock worked like a charm. Just needed something to fit over shaft and contact inner race of the bearing. Don’t use the tapping in a vise trick on the new bearing, can damage it.
I have started to stay away from cheap Chinese bearings. They always seem to have a loose fit.
The new bearings we tighter than the old so I had to press them on. I don’t have a bearing press but the lathe tail stock worked like a charm. Just needed something to fit over shaft and contact inner race of the bearing. Don’t use the tapping in a vise trick on the new bearing, can damage it.
I have started to stay away from cheap Chinese bearings. They always seem to have a loose fit.
You never know, it's worth keeping around.
When the armature shaft on my Problematic 4224 broke, it was out of warranty and they wanted almost $1000 for a new one. I bought a used Baldor 3hp motor on eBay and adapted it to fit. I was able to get a pulley on the broken stub and mount it on my Jet drill press. Now, instead of swapping belt positions to change speed, I use the buttons on the VFD to go up or down. Of course 2hp (my 4224 had 2hp, not 3
) is way more than I need on a drill press, but I really like the electronic variable speed.
Many years ago I worked in an apparatus repair plant where the main subject for repair was specialty motors that couldn't be purchased as timely as repairing the original and the first order of business was to dismantle the motor. When repairing those motors they always put new bearings in. The tools used included lengths of pipe to seat or press the bearings on, presses and a small oven set to about 150 degrees F. The most common method used was to put the bearing in the oven, then when hot rapidly slide it on the shaft. The heat expands the inner race enough that it slides on, then the cold shaft will cause it to shrink in place and a sharp tap on the appropriate sized pipe will seat it.
I called a motor repair place last week as the bearings are going out on my dust collector. $200-250 typically for a 3hp motor. That seems worth it to me.
Since it’ll require a complete disassembly of the collector I’m debating building a free standing sound deadening closet for it.
Since it’ll require a complete disassembly of the collector I’m debating building a free standing sound deadening closet for it.
I ordered electric motor grade Nachi replacement bearings made in Japan and will visit HF for a puller. There is so much dust built up in the motor that it makes me wonder about the longevity of any lathe motor that is not mounted in a cabinet. Has that been discussed previously? I also noticed that the Marathon motor I am repairing has a 56CZ-80 frame, which I think translates to a non-standard shaft. The shaft is tapered and the pully has a matching taper. I was a bit baffled at first when I couldn't find a keyway and grub screw. My guess is that it would be difficult to even find a replacement motor with a suitable shaft and I wonder how many models of lathes are manufactured with non-standard motors and other parts. As it stands, this lathe is probably scrap if I can't get the motor running smoothly. Maybe I can convert it to a pole lathe.
Since motor bearings are typically easier and cheaper to replace than an entire motor, replacing the bearings is generally the better first step. You don’t need to replace the motor unless there’s a larger issue with the motor itself or the bearings are inaccessible. Motor Spherical Roller bearings are a relatively low-cost part, and with a little bit of research and effort, you can usually find a suitable replacement.
Last edited:
Agreed. I replaced the bearings and the lathe is back up and running. The interesting thing is that the local motor shop could not do the job economically relative to the cost of a new motor.
It can take at least an hour to replace electric motor bearings. The actual pulling off and pressing on off the bearings was rather quick taking maybe 10 to 15 minutes if you've got a press and pullers handy. Its getting the motor apart and putting it back together that can eat up lots of time, particularly on single phase motors. There's also the issue of having the bearings in stock. Most motors use the 6200 series bearings but not all. That's when you'd better be prepared and experienced. I have found that Asian-made motors were a little easier to work on but their catastrophic failure rate was much higher.