Table Saw Vibration

[Harvey Pascoe]

I just finished rebuilding my Delta Unisaw - new motor, bearings and belts. We had wrongly diagnosed bad bearings in the motor because we thought we detected movement in the shaft when prying lightly on the lower pulley. Ordered a new one, but when we pulled the old one out could find nothing wrong with it. The saw had been making noise like bad bearings but we got fooled on that, too. Using a hammer handle as a stethoscope on the bearings, heard no unusual sound. But once I got them out, oh boy, one of them was definitely bad.

With everything replaced when I fired it up I expected it to run perfectly smooth. It did not, it had a low vibration that seems greater than before (I'm not totally sure of this). When I place any number of small metal objects on the table top while running, they do not move yet the vibration is enough that I can feel it. Perhaps my expectations for smoothness are unreasonable, I don't know. Should this saw run perfectly smoothly or is this degree of vibration normal.

The new motor, 3 hp Leeson is not as quiet as the orginal.

I see one possible cause. Although the belts are new, one is clearly a bit larger than the others as it does not pull as tight ; there is visible flutter but certainly not extreme. Also, the upper and lower pulleys do not and never did perfectly line up- they're 1/8" off.

[Lee Schierer]

An eighth of an inch is a lot of misalignment for pullies. I would see what can be done to get the alignment closer. Otherwise you will have premature belt wear and probably more vibration than you would get with aligned pullies. With regard to the belts did you buy a matched set? If not take them back if they are not damaged and get two that are the same size.

[Frank Drew]

The classic, low tech, test for vibration is to see if a nickel (or even a dime!) will balance on edge with the machine running.

[david brum]

You might try running it with just one belt to see if that eliminates vibration. If the vibration is gone, you'll at least know where your problems are coming from. I don't know if other guys are doing this, but I replaced all of my machine's belts with link belts a few years back. The cabinet saw has been running great with link belts, much better than with the stock belts.

[Steven Wayne]

Harvey,

I went through this when I went through my new-to-me Unisaw earlier this year. I have a thread about my saw here: http://www.sawmillcreek.org/showthread.php?160464-73-Unisaw-Resto-Mod

I (http://www.sawmillcreek.org/showthread.php?160464-73-Unisaw-Resto-Mod)t is VERY important that you use three matched belts. The information is in my thread. The previous owner had used link belts and they were much worse than the Napa automotive belts that he included with the sale. I bought the proper Delta replacement matched belt set and the saw runs smooth as silk. Check out my saw thread. I think it will help.

You need to align those pulleys as well.

[Harvey Pascoe]

Harvey,

I went through this when I went through my new-to-me Unisaw earlier this year. I have a thread about my saw here: http://www.sawmillcreek.org/showthread.php?160464-73-Unisaw-Resto-Mod

I (http://www.sawmillcreek.org/showthread.php?160464-73-Unisaw-Resto-Mod)t is VERY important that you use three matched belts. The information is in my thread. The previous owner had used link belts and they were much worse than the Napa automotive belts that he included with the sale. I bought the proper Delta replacement matched belt set and the saw runs smooth as silk. Check out my saw thread. I think it will help.

You need to align those pulleys as well.

Thanks, I will. I knew there was a recent thread on this but couldn't find it.

BTW, those pulley's have been misaligned for 17 years w/o vibration and the original belts lasted that long. I've had the top off twice in the last two weeks and I'd do just about anything to avoid doing it a third time, including living with the vibration. My belts are Delta belts, purchased after a set purchased from ebay were even worse. They have been on for 6 months and show no wear.

I just tried the nickle test and it will stand up most of the time. My saw is not perfectly level so its hard to keep it from rolling. However it does not remain perfectly still, it moves a bit. Its hard to make a nickle stand up with the saw turned off, so I wonder if I'm not being overly sensitive about this.

[Harvey Pascoe]

After looking at the belts I think I see the problem. The loose belt is the one at the blade end and this suggests to me that the motor pulley horizontal parallelism is not aligned with the arbor pulley. This further suggest that the motor is not level, but cocked a degree or so and this most likely is due to wear on the bolt holes, or the large clevis pin that supports the motor. This pin took quite a beating getting it in and out twice, but then so did the holes.

The motor is brand new yet this misalignment was there with the old motor as well where the same belt was looser than the others, the same then as now.

Here's and interesting fact: When my arbor bearing went bad I was very surprised to find that it was the non-loaded end of the shaft where the bearing went bad. I would have expected that it would be the blade-end bearing. When I mentioned that to an engineer friend of mine, he smiled and said that is always the way it is, and then explained why. Its a complicated answer but when you suspect bad bearings either in the arbor or the motor, always check the non load bearing end of the shaft first.

The reason is that when the loaded bearing gets a slight amount of wear, this causes the other end of the shaft to oscillate and place an uneven load on that bearing that ultimately causes its failure. So you do need to replace both bearings even if only one seems to be bad.

[Gary Kman]

You replaced the MOTOR, vibration starts, much work and discussion on BELTS. Hmmm?

[Harvey Pascoe]

You replaced the MOTOR, vibration starts, much work and discussion on BELTS. Hmmm?

Does you comment carry an implication?

[Steven Wayne]

I don't think you should be able to see visible fluctuation in one belt. You could put a dial indicator on each groove of the pulleys and look for runout. Perhaps you have a bad pulley. Did you install your belts in the order they were made on the mandrel? When I did this my minimal vibration went away.

Something else I did, before the belts that helped a good bit of the vibration I was noticing was to adjust my mobile base so that the saw was on all four feet (two wheels and two rubber feet) when the stand was parked.

[Harvey Pascoe]

No, I didn't put the belts on in any particular order, didn't know there was an order. I'm going to try switching the belt positions. I still suspect the motor mounts and need to look into that.

Both motor and pulley were dialed before being installed. OK

My saw is sitting on concrete and this is no help, I'm sure. I will try some thin wood shims and see what happens. If reduced, I'll look for some hard rubber.

[John Lanciani]

New motor is louder, mount is welded crooked, and it vibrates more than the old one...the concrete floor is not the problem. As for the belts, skip Delta or
Grizzly, go to a bearing supply house and get a fresh set of Gates or Goodyear power transfer belts. Cure the disease, don't just treat the sympoms.

[Harvey Pascoe]

I placed pieces of inner tube under 4 corners of the base. WOW, what a difference. runs much smoother and quieter now. Possibly the floor was slightly uneven and that was part of the problem. I'm done with spending my days on hands and knees under the extension table and inside the saw. I'm too old for this. While not perfect, I can live with the small amount of vibration that remains.

[Harvey Pascoe]

Just as a follow-on to this vibration problem, I bit the bullet and pulled the table top for the third time and aligned the upper and lower pulleys (were 1/8" out) when the vibration got worse and then started to make noise. Never would have guessed that that little deviation would cause that much vibration, but it did. Now the nickle stands on the top without moving a bit and the saw runs with just a hum - as it should.

[jeff vanek]

i put link belts on my unisaw yesterday and it made a world of difference, in the vibration and the start up thump.