Best Way to Test for Bent Table Saw Arbor

[John Goodin]

I noticed some wobble in the table saw blade as it slows to a stop and think the arbor on the saw may be bent. What is the best way to determine if it is and what is the best solution? And how would an arbor get bent? It is a popular Grizzly model still in production so hopefully parts are available. Thanks.

[Gerry Grzadzinski]

Put a dial indicator on it.

[Ben Rivel]

Dial indicator. I have used both the Betterley UNA-Gauge and a Starrett mag base w/ arm to hold the dial indicator. But there are many options out there.

[Doug Hepler]

John,

To address your second question first- I can't think of any event in the use of your saw that would bend the arbor. I think it is much more likely that the blade isn't flat or that a bearing is worn. Now to the first question. As others have suggested, use a dial indicator. If you don't have one, they are readily available and not that expensive. However, you need a dead flat disk to bolt on the arbor. Some sanding disks will work, or a blade stabilizer. Freud sells a calibration and sanding disk that should work. Finally, you need a way to fix the dial indicator to the saw table. You can use a magnetic base or a fixture that goes in the miter gauge slot.

Doug

[mreza Salav]

As said, dial indicator.
I don't think you need a flat disk though. All you need to do is to check the run out (if there is any) at the flange.

[Ben Rivel]

Like so: LINK

Measuring-Run-Out-on-Flange-Grinding-Table-Saw-Arbor-Flange.jpg

arbor_runout_1.jpg

[Pat Barry]

I think you should try to determine first if the blade is wobbling left to right, which is more likely a bent blade or not properly seated blade, or if it is wobbling up and down.
Make a shallow test cut in a piece of plywood (at least deep enough such that several saw blade teeth are engaged in the cut - maybe something like 3/16 deep). Then remove the blade and test the fit of the blade into the saw kerf. If its a close fit then the bladde is not wobbling left to right. If its a very loose fit then you could have wobble due to either that blade being bent or not properly seated.
Now put on another blade and repeat the procedure. Same results - suspect the seating plane, different results - suspect the blade.
Assuming you have narrowed it down the the seating plane, which could be a bent arbor or might even be some kind of a burr that keeps the blade from seating, then you can go the dial indicator route.

[Erik Loza]

As others have said, dial indicator. Every ww'er needs one of these. Good for all sorts of stuff.

That being said, I would suspect a bad blade or possibly bearings before the arbor itself. I can't image how you could actually bend a saw arbor. Best of luck.

Erik

[glenn bradley]

I would put a different blade on and look for the same behavior. This would quickly tell you how to proceed. Another quickey is to unplug the saw, hold a piece of scrap or clamp one to the miter gauge so that it is just touching the blade blank (not the teeth). Slowly rotate the blade by hand and look for misalignment. Grip the blade body firmly but, gently and try to move it about; is there any slop? I agree that an inexpensive dial indicator is a must for any woodworker.

22124 Alingment 004.jpg22124 Alingment 010.jpgalign on the cheap.JPG

[Michael Dye]

I agree with most that the arbor, itself, would be hard to bend while on the saw. That being said, I purchased a Delta Unisaw from a boat manufacturer years ago. The saw had been mostly used for cutting aluminum and, due to that, had a worn out arbor. I ordered a new shaft and washer, installed the new washer (press fit) and discovered about a .020 runout on the face of the washer. Luckily, I have the equipment necessary to remove that runout. You might want to look at the flange of that thick washer and see if your runout is there. Worth a look.

[Martin Wasner]

There's also some harmonics at certain rpm that will make blade wobble. I can see it in every saw we've got when either spinning up or after cutting power.

[Warren Wilson]

You might enjoy this video -- posted today by Matthias Wandel:

http://woodgears.ca/saw_arbor/index.html