Help with Saw Bearings

[Kurt Wyberanec]

Hello all....I have a JET 3hp Xacta cabinet saw, about 2003 service and I need a bit of help. My saw used to run nearly dead quiet and very low vibration. I've noticed over the last year or so that it is getting louder and more vibration. My thought is that a bearing is going somewhere or maybe a belt flat spot or something. I don't have a lot of experience working on or diagnosing motors, and I can't afford for my saw to be down to take it out for service so I need to have a clear idea of what is wrong before I could do so. I am planning on upgrading this year (that will be another post soon) but even if I order now I probably wouldn't see it for some time.

My question is how can I track down this noise and tell which bearing or component it might be coming from. I obviously can't fiddle in there while the saw is running so what would I need to take apart to be able to find it with the motor turned off and how?

The saw does not appear to be losing any power or having any problems cutting so it doesn't seem to be impacting performance at this point, with the exception of vibration.

Any thoughts or advice would be most appreciated. Thanks!

[Alex Zeller]

On my PM66 I could tell the bearings were about to go after I removed the belts. When I spun the blade you could feel they were dry. They didn't make any noise though. A good bearing has a little bit of resistance to it. Both the seals and the grease inside it resist the bearing turning. It's not much and it feels smooth. My bearings had no resistance and I could feel a slight vibration. Unfortunately it wasn't until I had them out that I could tell much easier. 19 years of usage could have your bearings ready for replacement. Most likely you can buy replacement bearings for a fraction of the cost of "Jet" brand bearings. I personally like Timken bearings but there's plenty of great brands. I'm not familiar with how to replace them on your Jet saw. On the PM66 it's not a hard job but I have a hydraulic press that made it easy.

[John TenEyck]

I would first check to make sure the pulleys are tight on their respective shafts. If so, then I'd remove the belt(s) and just run the motor. If you hear vibration then that's the source of your problem, either a bearing or maybe the motor is loose on its mounting plate/cradle. If not, while the belts are off, turn the arbor by hand and listen and feel for any noise, hesitation, anything other than completely smooth rotation. Also, try tipping the sawblade left/right, rotate a little, repeat a few times, again looking/listening for anything unusual. Check that the trunnion is firmly bolted to the cabinet or underside of the table, whichever the case may be with that saw. If you hear or see nothing, anywhere, I'd replace the belts and try it again under power.

John

[Kurt Wyberanec]

I would first check to make sure the pulleys are tight on their respective shafts. If so, then I'd remove the belt(s) and just run the motor. If you hear vibration then that's the source of your problem, either a bearing or maybe the motor is loose on its mounting plate/cradle. If not, while the belts are off, turn the arbor by hand and listen and feel for any noise, hesitation, anything other than completely smooth rotation. Also, try tipping the sawblade left/right, rotate a little, repeat a few times, again looking/listening for anything unusual. Check that the trunnion is firmly bolted to the cabinet or underside of the table, whichever the case may be with that saw. If you hear or see nothing, anywhere, I'd replace the belts and try it again under power.

John

Thanks guys, I was trying to think how to isolate the parts and it sounds like taking the belts off would be able to eliminate the bearings on the arbor. Is there any risk to running the motor without the belts attached? I know in some case they're designed to have load and running with no load can damage?

In respect to making sure all mountings are secure, totally makes sense...downside is the cramped confines of getting in there to try and check

Does anyone think that the belts themselves could at all be the issue? They appear to have the usual tension on them.

Overall it's been a very good machine to me with little headache.

[John TenEyck]

You will not hurt the motor by running it w/o the belts. You hurt an electric motor running it with too high an amp draw; w/o the belts it will draw the minimum possible for that motor.

Yes, the belts could be the problem. Frayed, partially broken, a missing chunk, or a permanent set could all cause vibration. Easy enough to check.

John

[Colin Busby]

Heat can be another telltale for bad bearings. Run the saw for 5 or 10 min, then turn it off, unplug/disconnect, and feel around. Or if you are lucky and have an FLIR camera just use that. Less work than taking the belts off, but ultimately that is what you will end up doing to confirm. Spinning the motor shaft and the arbor by hand once the pulleys are off should give you the answer.

[Robert Engel]

If it’s that old it’s very likely arbor bearings.

I had the same saw (2001). It’s a bit if a job you have to remove the top. That could e tail removing the wings unless you have some hefty help.

Two things I learned, one VERY important.

1. The retaining nut (other side of arbor plate) is LEFT HAND THREAD on a left tilt machine.

2. You have to be careful about realigning top or the ZCI will not line up exactly. I suggest putting a blade on while you’re doing it.

[Bill Dufour]

Old school trick is to remove the blade then use a long, small stick of wood touching each bearing in turn while running or hand turning Put the other end of the stick into you ear and listen for growling noises. They sell mechanics stethoscopes with long ridgid probes for this
Bill D

[Lee Schierer]

Unless this saw was in a production shop and used for hours every day, I doubt it is the bearings. It won't hurt to remove the belts to check the motor and arbor bearings. I have a Craftsman TS from the 1980's and the bearings in it are just fine. On the other had cold weather and/or infrequent use can cause the belts to take a set which results in excess vibration until the belts warm up. Cracks in belts or pieces missing can also cause vibration.

[Jerry Bruette]

Old school trick is to remove the blade then use a long, small stick of wood touching each bearing in turn while running or hand turning Put the other end of the stick into you ear and listen for growling noises. They sell mechanics stethoscopes with long ridgid probes for this
Bill D

A long screwdriver or pry bar with a plastic handle works well too.

[Bill Dufour]

A screwdriver has the advantage that it will not scratch up the inside of your ear. And it is too large to touch the eardrum if something bad happens.
Twenty years is not bad for grease life if you think about it.
Bill D.

[Ronald Blue]

A screwdriver has the advantage that it will not scratch up the inside of your ear. And it is too large to touch the eardrum if something bad happens.
Twenty years is not bad for grease life if you think about it.
Bill D.

I agree with Bill that the bearings are a good possibility. Grease does lose some of it's lubricating characteristics over time. Especially in a sealed bearing where the quantity is minimal. Do all the diagnostic checks already suggested and even if the belts end up being the cause of the vibration I would make a plan to replace the bearings on the arbor. Motor bearings could also be the culprit. Quality bearings aren't that expensive and it would be good for another 20 years.

[Brian Runau]

Kurt, if your pulleys are misaligned this can create noise and vibration. My opinion, a failing bearing is a high pitched noise.

[Kurt Wyberanec]

Kurt, if your pulleys are misaligned this can create noise and vibration. My opinion, a failing bearing is a high pitched noise.

Thanks guys, I will definitely do some of these checks and see what I can find. I am a light duty professional but it's a one man shop. My biggest challenge is that I haven't done much of this diagnostic work.....quick question though Brian, the noise I have is more of a raaaaaaa kind of sound not as high pitched as say a router running, but not exactly a grumble either. How would I be able to tell if the pulleys have somehow gone out of alignment? The saw did undergo a shop move about 2.5 years ago, but I can't recall as to when I started to notice the noise increasing....might have been before but at least a year now.

2nd question, if it is the arbor bearings, how does one replace them??? Can the arbor be removed and likewise brought to a shop to press them in (I'm assuming they need pressing)?

Thanks again!

[Ronald Blue]

I've dealt with lots of bad bearings in my career. They should roll smoothly and quietly. The first thing I always did was spin a wheel, hub, pulley or whatever. If you hear it then it's not good. Just make sure it's not anything else rubbing. Same with the motor when you have the belts off. As for pulleys moving? Anything is possible but unless you can see signs of movement or you can wiggle it then it's not likely the problem. Others can better advise on changing bearings. If you have the manual there should be a good break down of all parts but you can source bearings locally. Get an SKF or NTN or something similar. NAPA is often a good source for a reasonable price. If the Jet saw I looked up is the same it has the same size on both ends of the arbor. 6203-ZZ bearing.