# Possible bad bearing? How to tell?



## tymann09 (Mar 4, 2011)

Hey all. I was turning a large platter yesterday when I started noticing a strange noise on startup and slow down of my jet lathe. It sounds like once every revolution it is hitting something. I investigated a little bit and found that the top drive pulley is fine but the lower axle that comes out of The motor almost seems bent. When going very slow with it, it seems to wobble a little. Is this an indication of a bad bearing? I do have quite a few hours on the lathe but I guess I expected to get a little bit more out of it. Any suggestions would be great


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## Steve Neul (Sep 2, 2011)

Get a mechanic stethoscope and compare the sound of one bearing with another.


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## Hilltopper46 (Dec 29, 2013)

Not sure which Jet you have but the first thing to do in cases like this is to check the tightness of any set screws in the pulleys.


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## 9thousandfeet (Dec 28, 2014)

From your description I'm with Hilltopper. 
I would suspect a loose pulley on the motor shaft rather than a bad bearing. The symptoms you describe are those of something working loose more than those of a bearing going out.


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## tymann09 (Mar 4, 2011)

I've got a jet 1642 2hp. I will check the pulleys to make sure the set screws are tight. The sound I am hearing seems to come internally like something is rubbing but I will check.


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## hwebb99 (Nov 27, 2012)

Check the piece that the push button headstock lock engages into.


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## hwebb99 (Nov 27, 2012)

Here is the piece I was talking about. I have the same lathe as you, and the set screw fell out on that piece. It causes the same problem you describe.


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## Bill Boehme (Feb 9, 2014)

Hilltopper46 said:


> Not sure which Jet you have but the first thing to do in cases like this is to check the tightness of any set screws in the pulleys.


I also agree with your assessment. It is extremely unlikely that the motor shaft is bent.

Remove the drive belt and turn the spindle by hand to see if there is any noise or if the spindle pulley has any wobble. Do the same thing with the motor and its pulley. It might be that the keystock is the only thing that is holding the pulley. If the set screw is loose or missing, use Loctite to keep it from vibrating loose. Make sure that the key hasn't fallen out before installing a new set screw.


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## knika (Jan 15, 2012)

I have a Jet 1220 and had the same thing that you are talking about. After replacing the drive shaft bearings( the head stock) it turned out to be the set screw on the top pulley. I used some blue lock tight and have not had the noise since.


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## john lucas (Sep 18, 2007)

A common problem on just and powermatic is the set screw coming loose on the locking collar that works with the pin that locks the spindle. It can touch other things and give that once per revolution tick. Center it on the button and then lock it down


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## tymann09 (Mar 4, 2011)

Hey guys. Sorry for the very long delay. I only just got out to the shop today to look at the lathe. It turns out that I did indeed have a loose set screw. It was in the spindle lock collar thing. After toying around, I got the tick to go away. I do still have a slight wobble to my main drive shaft. Doesn't seem to be affecting anything though. Thanks for the help and suggestions!


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## Bill Boehme (Feb 9, 2014)

tymann09 said:


> ... I do still have a slight wobble to my main drive shaft....


What are you looking at that leads you to this conclusion? The best way to tell if the spindle is bent or has any free play is to run the lathe with nothing on the spindle nose (i.e., No chuck mounted NOR spur drive in the Morse taper socket). With the spindle speed about mid-range, feel with your finger inside the Morse taper socket to see if you can detect any wobble. It ought to feel glass smooth.

It would also be worthwhile to use a flashlight to inspect the Morse taper socket for any galling rings. If you have had a spur drive slip and spin, it will cause some metal smearing which will be seen as ridge and groove rings. That will need to be corrected before any of your drive spurs will run true. Repairing the damage is a bit expensive so the moral of the story is to not let it happen.

NOTE: It ought to go without saying, but I will say it anyway -- DO NOT shove your finger up the Morse taper socket as if it was a spur drive unless you want to have it wrung off. Just use the tip of your finger to feel near the end of the Morse taper socket. No need to go more than ¼" into the socket.


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## hwebb99 (Nov 27, 2012)

A dial indicator would be more accurate, and safer.


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## 9thousandfeet (Dec 28, 2014)

tymann09 said:


> I do still have a slight wobble to my main drive shaft. Doesn't seem to be affecting anything though


 Originally you talked about seeing a slight wobble in the motor shaft.
Is this the same wobble, or is the wobble you're seeing now in the spindle itself and not in the motor shaft?


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## tymann09 (Mar 4, 2011)

I guess I must have misspoke. The wobble is coming out of the main shaft, directly out of the motor. The actual drive shaft seems fine and I've never had a problem with turnings.


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## Ron Rutter (Jan 18, 2011)

Is it actually the motor shaft or the pulley you are looking at. A bent motor shaft would be odd.


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## 9thousandfeet (Dec 28, 2014)

OK, so it's the same wobble you mentioned initially, on the motor pulley not on the spindle pulley.

It's unlikely the motor shaft is bent, but it's possible the motor pulley is not _totally _free from a little runout.
I imagine you checked to ensure the set screw was snug when you were chasing that clicking sound, so if there are no symptoms—if the belt is tracking fine, and there's no weird noises or troublesome vibrations and it doesn't affect your ability to turn and enjoy the process, then maybe you're good to go.


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## Bill Boehme (Feb 9, 2014)

tymann09 said:


> I guess I must have misspoke. The wobble is coming out of the main shaft, directly out of the motor. The actual drive shaft seems fine and I've never had a problem with turnings.


I would look at the motor shaft and not the pulley when trying to determine where the problem lies. In all likelihood any wobble that you see is coming from the pulley.

Much of the misunderstanding comes from not being familiar with the commonly used terminology which is no sin -- we all were beginners at one time or another. The "shaft" in the headstock is called a spindle. The "business" end of the spindle that is threaded and has a Morse taper socket is the "nose" of the spindle. Sometimes the pulleys are called sheaves, but that term seems to be fading into disuse. The banjo is sometimes called a tool rest base. The "ways" are the two parallel flat surfaces of the lathe bed. Everybody knows what "legs" are, but some lathes have metal bases that look more like cabinets or in some cases you provide the mounting surface (that is the case for most mini lathes).


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## tymann09 (Mar 4, 2011)

I am back!!! After turning several more bowls, tonight I was turning a spindle and all of the sudden things went bad pretty quickly. The noise I was experiencing before became much louder and pronounced. After rechecking all the pulleys and set screws which were tight, I moved to the motor. The motor was extremely hot, almost too hot to touch. I pulled the end cover off and pulled the fan off, ran it and still heard the noise. I gripped the axle from that end and spun it and could feel friction. I put one hand on the motor and spun it by hand and could feel it.:thumbdown: I am now worried that during my recent move, something got off balance from being bumped or something and is just getting worse. It is to the point where the lathe should not be used and I'm right in the middle of a job too!!! :furious: Anyhow. Since the problem seems to lie within the motor, what should I do? Send it back to jet for repair? Help please!!!!


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## Ron Rutter (Jan 18, 2011)

Most likely the bearing on the pulley end. Remove the other cover & pull out the rotor & check the bearings. If it is really noisy one is probably seized. If you don't have the means to pull the bearings take it to motor or mechanics shop. Ron.


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## epicfail48 (Mar 27, 2014)

If the motor is getting hot to the touch, you've got a friction buildup causing excess heat, and one of the only thing that commonly causes that is a bad bearing. You could probably send the motor back for repairs, provided its under warranty, but replacing a bearing is such an easy process I'd say do it yourself. All you should need is a wrench, screwdriver and a 3 jaw gear puller to get everything apart, and a piece of PVC and a mallet to install the new bearing.


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## tymann09 (Mar 4, 2011)

Thanks for the feedback. Either of you guys know where I could buy a bearing? Is that something the auto parts store would have? If so what kind/size. The instruction manual isn't very helpful in that regard.


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## Bill Boehme (Feb 9, 2014)

The size and type will be marked on the bearing. Also check the centrifugal switch to make sure that it is working. You can't really tell much when turning the motor by hand since the switch will be closed and making a rubbing sound. The problem could be that the switch isn't opening as the motor spins up. This would result in excessive current in the start winding which would make the motor run hot and risk burning out the start winding. The wobble that you mentioned indicates that the problem might be a sized bearing with the shaft worn down. If so, the motor is toast.


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## tymann09 (Mar 4, 2011)

Bill thanks for the reply. How do I check the centrifugal switch? I'm planning on tearing into it when I get home from work this afternoon. I was considering bringing it machine shop since they would probably get it done quickEr than me


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## Bill Boehme (Feb 9, 2014)

tymann09 said:


> Bill thanks for the reply. How do I check the centrifugal switch? I'm planning on tearing into it when I get home from work this afternoon. I was considering bringing it machine shop since they would probably get it done quickEr than me


If you have a motor repair shop in your city then that would be the place to take it. A machine shop might not know any more than the rest of us when it comes to anything other than replacing the bearings. BTW, I meant to say "siezed" and not "sized" in the next to last sentence of my post. Sometimes these spell checkers are too smart for their own good.

The centrifugal switch is at the back end of the motor so when you remove the back cover you will see it. It consists of a mechanism with weights and springs and switch contacts. Several things that can go wrong with it are broken or loose spring, weight coming off the assembly, or pitted switch contacts. The contacts can often be cleaned up with a point file and crocus cloth. Any problem with the centrifugal weights or springs should be readily apparent. Here is one of *my posts in the AAW Forum* on centrifugal switches with some pictures. You can see the switch contacts, but the springs and weights are hidden from view beneath the switch contacts.

I should have first mentioned that if the motor is a half horse or smaller then it might not have a centrifugal switch. These smaller motors often have a start/run winding where the capacitor and start winding are permanently wired in. Those types of motors typically run hotter than the average AC induction motor. There are also larger motors for high torque applications that have two capacitors plus a centrifugal switch. The centrifugal switch switches out the start capacitor after the motor spins up and the run capacitor stays in the circuit full time to give the motor a bit of a torque boost under heavy load.


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## tymann09 (Mar 4, 2011)

I am back. I ended up taking the motor to an electric motor repair shop, the closest one for me was 45 minutes away. He said he'd get to it in two weeks. Well almost 4 weeks later, he called me up (today) and said he couldn't find anything wrong with it but said the bearings were in pretty tough shape so he replaced them for me. He also said he cleaned it up nice too. I had my fiance go pick it up for me since she works evenings and I work days. Turns out it cost $145, it looks beautiful but it is actually worse now than it was before. This is extremely aggravating. The poor woman I'm doing a job for has been patiently waiting for my lathe to be repaired and after 4 weeks I'm set back $145 and it's worse!!!! 

Bill, Thank you for all of the very useful information in the last post, I learned a lot about motors. I took a video of the lathe running with my cellphone and was wondering if there was a way to post it in here? I can also email it to anyone who is interested. I'm hoping the video represents the knocking noise i'm hearing well. Any input?


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## 9thousandfeet (Dec 28, 2014)

tymann09 said:


> Turns out it cost $145, it looks beautiful but it is actually worse now than it was before. This is extremely aggravating.


 No kidding.
But I'm struggling to understand why a motor repair shop would turn a repair job loose without quickly spinning it up on a test bench, and if they did that and the motor runs badly and is noisy, why in the world would they return it to the customer with a $145 bill?

You're saying the motor is now "worse now than it was before".
Your description of the motor initially was this; 
_"The motor was extremely hot, almost too hot to touch. I pulled the end cover off and pulled the fan off, ran it and still heard the noise. I gripped the axle from that end and spun it and could feel friction. I put one hand on the motor and spun it by hand and could feel it"_
So are you saying that those symptoms are now worse even though the motor has new bearings and all the rest of the work done?

If you run the motor without the belt, so you're not driving the lathe spindle at all, is the motor noisy and running badly? 
If it is, then I'd take it back to the repair shop and insist they put it on a test bench while I was there.

Can't help with how to upload video, I'm afraid.


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## tymann09 (Mar 4, 2011)

I too was really ticked to see that it was worse. They even put a new paint job on it I'm pretty sure. I wish I could put a video up. It sounds insane. However, I pulled everything apart and looked inside. The coil laminations have striations on them from where the shaft was hitting. I did some research and found a thread on sawmill creek forums with the exact same issue that I have. Long story short, they've said jet manufactured a line of defective motors around 2003. My lathe was manufactured in 3/2003. Apparently the shaft steel wasn't hardened properly and it fails over time. I really have no time to take off from work so can't go back to the shop to demand my money back. I think I've concluded that my motor is toast. Oh well.


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## Bill Boehme (Feb 9, 2014)

Is your lathe a Jet? If so, which model? Does it have Reeves pulleys or fixed pulleys? If fixed pulleys, does the lathe have electronic variable speed?

When you are running the motor after it has been "refurbished", is it installed on the lathe or just sitting on the bench running without any pulleys?

The reason for these questions is that I am trying to determine the type of motor and how it is being tested for noise.

Regardless of all my questions, I am shocked at what the repair shop charged. Maybe their main business is repairing industrial motors which are high dollar items. But, it sounds like maybe they didn't do the job right. Your experience is a lot different than mine with a local motor repair shop where they told me that a blower motor wasn't worth what he would have to charge to rebuild it. However, he scrounged some end caps with still serviceable bushings from some junked motors and just gave them to me. He also gave me some of the cotton fiber material that is an essential part of the oil circulating system that blower motors with bushings use. He also spent a lot of time talking about how this type of motor works and how the oil circulating system works. He then started taking the motor apart while we were talking and if I hadn't stopped him, he probably would have rebuilt it while we were talking. I thanked him profusely for being so very helpful and for refusing to take any money. He said that he also benefited from my engineering expertise so we both were happy in the end.


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## hwebb99 (Nov 27, 2012)

I think he has a jet 1642 which has a 3 phase motor with a VFD and a ribbed flat belt.


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## Bill Boehme (Feb 9, 2014)

hwebb99 said:


> I think he has a jet 1642 which has a 3 phase motor with a VFD and a ribbed flat belt.


Thanks, I missed that earlier and as a result some of my suggestions aren't applicable because they are for a single phase motor. It is altogether possible that the problem is due to a defective VFD. If the OP hasn't talked to Jet support, I think that it would be worth describing the problem to them.


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## tymann09 (Mar 4, 2011)

Yes it is the 1642 EVS 2HP with VFD. I am running the motor attached to the lathe with no belts on at all. I haven't yet called Jet nor have I called the repair shop to ream them out (hate doing that to people). I have concluded after a lot of research that I'm going to be stuck with getting a new motor. I think I'll do that and in a few years, sell it and upgrade to a mustard monster or oneway since I don't think the jet will last. I do a ton of turning.


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