Blade arbor - how worn is too worn?

[Jonathan Jung]

I recently got an Omga radial arm saw and have been going over it.

The main question is regarding the motor: how undersized or worn can a motor spindle be before it causes issues spinning a blade? It is 1" spindle, spins a 12" blade, and uses a keyway due to having a mechanical brake. Omga tech tells me a new motor spindle measures .999" with digital calipers. My spindle measures around .992-.995" (.005-.008" under). For comparison, the 5/8" arbor on my Sawstop measures .6235" (.015" under) and the 5/8" to 1" arbor adapter on my Makita miter saw reads .9985" (also .015" under). There's noticeable more slop with a blade on the Omga than with a blade on the miter saw or table saw. But is it enough to worry about? I don't see the slop introducing blade wobble, with the massive blade washers there. I'll be using the radial arm saw for general crosscutting and I do want it to cut well. A new motor is $1300.

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[Jared Sankovich]

More radial runout will cause a larger out of balance scenario. It may cause enough increased vibration to be problematic.

[Richard Coers]

Clearance of the blade hole and the arbor will not affect nut tightness. If that was an issue, every Harley motorcycle in the world would be laying in pieces on the highway. No wait......LOL Jared is right, only limits vibration.

[Edward Weber]

There is no reason why an arbor should wear like that. I would say that the previous owner/s didn't know what they were doing. It looks like the arbor was just sitting there spinning, and the blade wasn't, wtf

Without even knowing the numbers, just looking at it, I would be concerned and probably replace it.

[Jonathan Jung]

It looks that a previous owner ran wide blades or dado stacks without the key, so every time the brake engaged to stop the spindle the blades spun a little. Also it doesn't have soft start. I'm guessing after thousands of starts and brakes the blades wore on the spindle. The saw is designed to be turned on, left on for an entire batch of parts, then turned up.

[Patrick Kane]

I had a pm72 with a worn arbor, and i only ever noticed it with running wide dado stacks. The bottom of my dadoes would have ever so slight discrepancies between the chippers. Going off a 3-4 year old memory, my arbor looked worse than your arbor. Never noticed any issues ripping or crosscutting with the saw, just the dadoes.

[Larry Frank]

If your Sawstop measures .6235, then it is only 0.0015" under size.

[Bradley Gray]

I would put your intended blade on the saw, make some cuts and see if you find the results acceptable.

[Richard Coers]

If your Sawstop measures .6235, then it is only 0.0015" under size.
Yup, he better get a calculator! If you demand pure precision, take it to a motor shop. They can build up the shaft with a laser or flame spray and then turn it back down. Spun a bearing on a Griggio slider once and the motor came back like new. Not cheap and not every motor shop has the capability.

[Brian Runau]

I was a salesman for Chicago rawhide oil seals. We sold an item called a speedi sleeve to repair shafts from seal wear. You use metal filler and slide this on, once it sets up, new seal surface. Not sure if this would work here, but a shop could potentially weld it up and turn it down, I would think for less money.

[Greg Quenneville]

+1 on the shaft repair. That saw is too nice a machine to use with anything less than the original fabled precision.

[Ronald Blue]

Put a blade on and try it. You are talking .0025-.004 per side. I'm guessing you won't notice it especially since you only plan to cross cut with it. If the blade doesn't wobble side to side it shouldn't affect the cut quality. Compare smoothness when running without and with a blade mounted. Don't over think it unless it's necessary. Only if it causes an issue would I seek a solution.

[Steve Rozmiarek]

I let one of those get away on a local auction recently, still kicking myself. I doubt you will have runout problems. Where you put your dial caliper on that shaft will likely yield different results. You'll probably find that there are places that it actually reads in spec or slightly higher as the metal from galling didn't leave the shaft when the blade spun, it just moved it. You will probably find measuring the diameter runout of a blade, you get different results than just measuring the shaft. My guess is that you will find it's a non-issue in practical use, you might just have a cosmetic decision to make. Oh, good luck getting a blade that's +/- .001 for a solid test, you might have to try a few.

[Bruce Wrenn]

Could you have the shaft plated to build it up?

[Bill Dufour]

You could do it with JB weld then sand it down. have a one inch bore shaper cutter to use as a a go/no go guage?
Bill D

[Edward Weber]

The only problem I see with doing a patch of some kind is that if you do the same thing as the previous owner and don't tighten the blades properly. A spinning shaft inside a slipping blade will just destroy any quick fix.

[Ronald Blue]

Determine if it needs fixed first. Most people would have put a blade on and been enjoying the machine already. As I said in a previous post unless you have side to side runout it shouldn't be an issue. If you do you may have a different problem to resolve.

[Brian Runau]

https://www.mcmaster.com/speedi-sleeves/

[Jonathan Jung]

Thanks everyone for the replies. What prompted asking the question and not just testing the machine is that it still needs to be hooked up. In order to run it I either have to spend about $300 on a long power cord, plugs, and outlet boxes at my 440v transformer, to get across my shop to from my 3 phase, or convert to 220v and spend $450-650 on a VFD to run off 1ph. I was thinking that if the spindle is indeed shot, then I'd skip the 3phase hookup or VFD and just order a new motor in 1 phase. Two birds with one stone. But it looks like I should definitely try the machine as-is, so I'll spend the couple hundred on a SOOW cord hook it up as is.

[Bruce Wrenn]

Machine glued to the floor Why not move it near power source and try it out?