TS arbor nut suddenly over-tightening in use

[roger wiegand]

I'm experiencing a new problem on my PM66 table saw that I've been using for the last 40 years. The last two times I've changed blades I've discovered that the arbor nut has tightened itself during use almost impossibly tight. The last time I took the blade off I needed to hold the blade with a C-clamp wedged against the table and a breaker bar on the arbor nut. Nothing like this has ever been required on several thousand previous blade changes. Threads all look good and clean, the nut threads on easily. I did notice some abrasion on the surface between the nut and washer so I flattened both surfaces on a stone. That didn't help the problem, after very brief use it was again similarly tight. I'm not happy of clamping the blade like that as I worry about warping it. (unfortunately there are no accessible flats on the other side of the arbor to hold it with a second wrench)

My usual practice is to thread the nut on snug and then tighten the nut with the wrench while hand-holding the blade. So not very tight. As the blade spins it tends to tighten up, but never so much that I've had any problem loosening it by just holding a block of wood against the saw teeth and using the wrench.

Any ideas what might have happened? Or suggestions for a solution? A plastic shim would probably let me get it off easier but at the cost of possible run out. I'm leery of adding a lubricant (teflon or graphite?) for fear that it might not hold as well, but will try that if others have had good experience.

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[Doug Garson]

Is the blade dull or dirty and thus causing more resistance to cut thru the wood and then causing the nut to overtighten?

[Richard Verwoest]

I have also had this experience with my Grizzly tablesaw. I noticed a week or so ago the drive belts looked old and sloppy. So I ordered new ones, but have not installed them yet. Your post got me wondering if the loose belts could somehow cause this?

[Jimmy Harris]

I've used WD-40 before. Not as a lubricant, but as a rust preventative and didn't run into problems. I don't know if that would fix your problem, but I doubt you'd have problems with the nut coming loose on it's own. My guess is you'd likely have the opposite issue, if anything, since that's the way the saw's forces are acting on the nut.


I might try replacing the washer and nut, if you can. That would be fairly cheap, easy, and quick. It's possible that the bolt or nut threads have become worn and have too much slop in them, allowing the nut to turn past where it should. Or the washer is too grippy and not letting the nut slide. It could also be a bearing issue, though I don't know how likely that is. Like the bearing is generating too much heat on the arbor, which is expanding and contracting and allowing the nut to tighten further than usual when hot, and then jamming it in there when it cools off. So if you do decide to replace the arbor, I'd also do the bearings.

[Mike Henderson]

I've had that problem when I didn't tighten the nut tight enough when changing a blade. Try tightening it a bit more before using the saw.

Mike

[Wes Grass]

Some story from long ago. Spin it up close and fire it up ... major hassle to get it back off.

One of the reasons I like the dowels on my Felder.

[Tom M King]

I use the wrench slam technique to loosen the nuts on table saws, radial arm saws, bench grinders, miter saws, and such. Use a block of wood to slam the wrench down on. Nothing ever touches a blade to put any kind of force on it. The same technique going the other way, only Much lighter, tightens the nut.

[Warren Lake]

never had that happen on any of my saws general or SCM so cant see what caused it. To loosen blades I just stick a piece of wood into the teeth closest to operator, wrench on and pull it towards you. Simple and easy and no damage to anything. Maybe some saws have a spindle lock like a shaper, maybe the SCM never looked close enough only used wood blocks on any saw . TIghtening only ever used hold blade left hand and wrench to the back till snug.

[Thomas McCurnin]

+1 on what Warren does.

[les winter]

You may be running out of thread and the nut is cutting its own way. Has the washer flattened?

les

[roger wiegand]

Warren's method is what I typically do, in this case I couldn't wedge it with a block of wood, the blade would simply cut through the block. I couldn't hit it hard enough or fast enough to get the wrench slam to work.

What seems to have worked however was a very thorough and careful cleaning of the nut and arbor threads. I noticed a little drag while tightening the nut for the final turn, which made me suspicious. I soaked the parts in Simple Green for a while, scrubbed them with a wire brush, then scrubbed them again with some lacquer thinner. Following that cleaning the drag on the last turn was gone and the nut has come off easily twice so far. So I think it was a small amount of schmutz in the threads that was causing it to bind.

Thank you for your ideas!

[Jimmy Harris]

There you go! It looked clean in the photo, but photos don't always tell the whole story.

[Steve Demuth]

I would try to determine if the blade is move against the arbor flange after initial tightening and installation. If it is, then the arbor is probably moving under the whole blade-washer-nut combination, resulting in the nut being drawn overtight.

Why would this change now? Different blades? Arbor flange has become too polished over time, allowing more movement than before? Some sort of lubricant got on the flange? Change in where you store you blades, so they've got lubricant on them?