Cannot loosen arbor nut

[Bill Stark]

Purchased a Craftsman 10” table saw, Model 315.228410, in October 1999 and have never had a problem with it until yesterday.  Put on a new blade and did a few cuts and then went to change the blade to my 8” dado blade. 
On this model, there is one arbor nut that locks the blade into place. On the other side of the blade is a tapered washer (for lack of better words) that is permanently affixed to the arbor shaft. In short, the arbor nut is threaded onto the shaft until the blade fits tightly between the tapered washer and the arbor nut. To remove the blade, you lock the blade in place with a piece of wood lodged between the blade and the cabinet and with the wrench, back off the arbor nut. 
That has worked fine for the past 17 years.  This time however, with the wood firmly locking the blade in place and wrench turning the nut (yes, turning the correct way), the nut is not backing off the arbor shaft and instead both the arbor shaft and arbor nut move together. 
I rotated and inspected the arbor shaft and found no damage to the threads so it wasn't cross-threaded.
My first thought for a solution was preventing the arbor shaft from moving by attaching and holding locking pliers onto the arbor shaft while turning the wrench but was worried the pliers would ruin the threads on the arbor shaft.
Has anyone had a similar problem or can anyone suggest a method to remove the blade???

bill stark

[AgGEM]

My first thought for a solution was preventing the arbor shaft from moving by attaching and holding locking pliers onto the arbor shaft while turning the wrench but was worried the pliers would ruin the threads on the arbor shaft.

bill stark

Yes, dont do that.
Might try to rip something hard for a few rips to warm the blade / arbor and with the saw then unplugged, hold some ice against the arbor for a few moments.
Then try to wrench the nut.

That you have been using this tool for so long does suggest that you know it well, and something new has happened.
Ag

[Mac1]

Go to the pulley side and remove the pulley. My Craftsman saw had a flat on the shaft for the setscrew to bear on. Use vise grip pliers and clamp on to the flat.  You can put a shim between the jaw that is not contacting the flat and the shaft.  Block the pliers to prevent rotation and have at it..If you damage the pulley end of the shaft, you can clean it up with a file.

[Wild Turkey]

I've put a piece of wood across the drive pulley under the belt so that when you try to loosen the arbor nut the wood wedges the belt in place and increases the friction.

Worked for me on a different Craftsman.  Hope it does for you!

[Woodshop]

some saws (like mine) have a hole in the end of the shaft for a allen wrench for time like these, you might check. but then mine has a interchangeable shaft also

[RPE1]

Or, I've just squeezed the belt to stop arbor rotation.  You can use a clamp, your hands, or whatever else you can dream up to squeeze the belt.
RP

[Cecil]

Or, I've just squeezed the belt to stop arbor rotation.  You can use a clamp, your hands, or whatever else you can dream up to squeeze the belt.
RP

+1

[Pirate]

Are you giving the arbor nut wrench a good whack with a 2x4?

[K. L. McReynolds]

The following advice has come up several times since I joined WN and, since I started following it, have had zero problems with the arbor nut on either my shop contractor Rigid TS2424 or my portable PC jobsite saw. The advice came from an experienced woodworker.

When tightening the arbor nut after replacing a blade, only tighten the arbor nut hand tight. The operation of the saw tightens the nut sufficiently during operation. Ripping 16' PT framing lumber, reducing sheet goods, what ever, never had a problem. And the nut is rather easy to loosen(there are flats on the arbor shaft to the inside of blade on my saw) so using two tools is done.

For your situation, holding the arbor shaft on the drive side of the motor may be the best idea. Might require two people.

[brianwelch]

Would it make sense to use never-seez (or equal) on the arbor threads to facilitate future nut removal (not over tightening is a great, but oft overlooked, idea)? 
I have a tendency to use it any place I anticipate repeated nut removal...