the usual reason for the flats is to prevent the arbor/shaft from rotating while one loosens/tightens the nut holding the blade on. is there any other arbor locking device on the saw?

can you describe the wobble a big more - a slight difference in diameter could make for vibrations, but should not let the blade move around.

 

I am trying to figure out why the washer you have is a problem? Have you checked carefully or are you just assuming the washer is causing a problem?

Wobble issue to me sounds more like a blade problem or bend arbor.

 

Can you tell more precisely what is causing the wobble? The washer with the flats is so small and light in weight that I would be surprised if it is causing any out of balance problem. If the blade is wobbling, I think there is another cause besides this washer. The inner washer on the other side of the blade could also be a cause. Or, the arbor itself could be the problem. I would be reluctant to change the outer washer without knowing, for sure, what the cause of the wobble is.

 

>is there any other arbor locking device on the saw?

There isn't. But any (I suppose) cast iron saw has no any flats and ok with it. In soviet literature I found a mention of that case, but there were flats on arbor only. In my case, flats with corresponding washer, it's more like hand-held saws -- preventing overtightening of the clamping screw/nut when blade gets stuck in material. But also for holding arbor while assembling the blade.

>can you describe the wobble a big more

It's interesting. Lets say, it is not constant. There are constant relatively small vibrations, but in some moment there comes a "hrrrrr" sound, and amplitude of shaking rises so much, that the riving knife begins to oscillate noticeable by eye (several millimeters, I think, in direction parallel to the arbor). That situation repeats randomly in 5-10 seconds, lasts for 1-2 seconds.

>Wobble issue to me sounds more like a blade problem or bend arbor.

Indirectly and touching the disc quality, the vibrations/wobbling/shaking situation could be also described this way. CMT brand blade, 10", that costs like a third of a saw itself and should give a "glue line cut", gives a cut quality like some random noname disc. And the second CMT blade, little less in diameter (216mm), results an accordingly less stress.

>Have you checked carefully or are you just assuming the washer is causing a problem?

I've measured radial deviation (what's the term?) on the washers. First one, counting from motor, gives 0,13 mm. Third one, outer, -- 0,15mm. So either the "circularity" of washers is compromised or they being clamped somehow with offset on the arbor (due to the gap of 16-15,875=1,125mm). Clear arbor rotation itself gives 0,014mm (approx. by eye on thousands), but the pressing down on it is measured in 0,02mm (flimsy construction of a support plate -- about 3mm of not-a-cast-iron metal sheet)

The deviation on the end (or face or face of a washers) gives 0-0,01mm on the inner and 0,05-0,06mm on the outer flange, but not sure that I measured it with the necessary accuracy. Outer flange was set inside out, for example, to contact a working surface.

BUT! In despite of all that measuring, I really only assume flanges' contribution to the vibration an wobbling. Earlier I've got some shims inserted in "sliders" (up-down rails in support plate) -- and that helped a little bit. And earlier more I've replaced a stock blade for CMT (that not helped).

Process of radial measurements on an arbor (similar to the washers):

End (face) measurements, not-so-accurate (forgot about tilting, outer washer is reversed):

 

the outer washer in pix 3 is installed wrong.
the boss with the flat edges goes on the outside.

if you have 0.13mm run out on the arbor, that's going to be a problem.

 

>the outer washer in pix 3 is installed wrong.

Yes, I've mentioned it. It's the only way to measure the flatness of its' working surface.

>if you have 0.13mm run out on the arbor, that's going to be a problem.

It is almost new. Hmm. I'll check it again, more accurately.

UPD 0,13 mm is the radial deviation on the first washer from motor. Arbor itself is 0,01(4?)mm.

 

Let's start from what "should be". If there is an inner "flange" check that for run out first. If there is only an inner "washer" .... put a short spacer and the nut on the arbor and snug it up to check it for run out. Now leave the spacer on and check the outer washer for run out. If the run out is .002" or so it's probably OK. Here's the problem with an arbor that is out of round ... you can't fix it. Here's the deal with a wobbly blade ..... it just makes a wider kerf, much like a "wobble dado". If your blade isn't flat YOU can't fix that either and you'll need to send it out for sharpening and flattening. I have sanded my blade washers on the inner surface to remove any uneveness. You can't really true up a blade washer unless you have a magnetic table and a surface grinder. It's cheaper to buy new IF you think your's is out of whack.