Unisaw bearings going???

[Mike Ruggeri]

I am starting to get some vibration in my Unisaw. First I thought it was the belts but now I don't think that is the problem (I tried several types of belts including the original, a link belt and a cogged belt and all seem to run the same). If I run the saw without a blade, it runs VERY smooth with no vibration. Once I put a blade in (I tried 2 different blades thinking my WWII might be bent or something), I get vibration. At this point the vibration is not excessive, but more than should be there (in my opinion). I am now thinking I should replace the arbor bearings. The saw is an early 90's model and has the original bearings and when I spin the arbor by hand (without the belts hooked up) it seems tights but the bearings make a very slight noise although no pronouced noise is noticed when the saw is running. Any thoughts or words of wisdom in my quest to make my Unisaw run smoother? Do you think its the bearings or something else causing the vibration?

Thanks

Mike

[David Christopher]

Mike, I would take the blade off and spray some PB blaster or kroil on the bearings and see if that smooths out the vibs and if it does then I would replace. the oil should give you idea if it is the bearings or not

[Pete Bradley]

I really don't get why one would spray penetrant on the bearings. If it gets past the bearing seals, you've contaminated the grease, if it doesn't it hasn't done anything.

A bearing swap on a Unisaw is not a difficult job and I'd probably do it on general principle. However it's hard for a bearing to generate noticeable vibration unless it's really, really trashed. I'd be looking for something that causes the blade to wobble, for example a burr, chip, or gunk that keeps the blade from sitting flat on the arbor, or an arbor out of true.

Pete

[Don Jarvie]

A few things to look at

When you turn the arbor without the motor attached it should turn smooth. If it sounds gritty or hard to turn then you may want to replace them.

Check the arbor without the blade with the motor running. Pretend you are checking the arbor for 90 to the table. Arbor should be straight up and down and left to right. The piece the blade will rest on should be straight

Also, do you use a washer between the blade and arbor? If so make sure the washer and the arbor washer are the same size in diameter and fit the arbor snug (no play up and down).

I restored my Walk Turner and put a smaller washer between the arbor and blade and the blade wobbled like crazy.

[Josiah Bartlett]

If the saw is more than 10 years old or so I wouldn't be surprised if the bearings were going. Sealed bearings seem to lose the grease effectiveness between 10-20 years old.

[Larry Fox]

Another thing to check is (are) the keyway and pulley. Mine was doing something very similar and they turned up to be loose. Easy fix.

[John Downey]

Sounds more like an imbalance problem than a bad bearing. Once a bearing gets so bad as to wobble, its usually been making an absolutely awful noise for quite some time.

[Ray Newman]

Use a shop-fabricated stethoscope.

Unplug the motor, remove the blade, and release the belts. Take a large diameter wooden dowel about 24" long and place one end against your ear, the other end by the bearing. Turn the arbor by hand and if the bearing(s) is bad, you'll hear a gritty noise.

You can also run the saw and do the same without the blade, and that will really amplify the bearing noise.

If the bearing(s) is bad, the best bearings will only cost a few dollars more than the so-called “economy grade” and be sure to replace all the bearings at the same time.