Dado Blade Keeps Coming Loose...

[Adam Kaufman]

Hi all, I've got an old Unisaw and I recently bought a Freud Dado for it. I'm real happy with everything except for the fact that when using the dado blade, the arbor nut likes to loosen up. I don't notice it until I turn the saw off and the blade free-spins for a while. Granted, I'm only doing quick, short cuts, and I have a felling the nut only loosens up when I shut it off, but it is worrisome.

I crank down the nut as best as I can, but it still happens. I suppose I just need to find a way to get even more torque on the nut.

Has anyone ever come across this? What's the best (and most economical) way to hold the blade while I tighten it? I've seen the blade holders - will they work on a stacked dado?

Thanks all!

[Larry Browning]

The threads on a TS arbor shaft are left handed so that the nut should not loosen from the torque of the spinning blade. If anything it should get tighter. The only thing I can think of is that the shaft may not be long enough for the amount of blade stack you have. The nut should not have any thread showing when tightened.

[Mel Fulks]

I've used only one saw that did that with dados .Did not loosen with a saw blade,just dados. If we tightened dados more than blade it would stay tight. It was a machine that seemed to have unusually high quick torque,if that's any help. I would consider using two nuts with dados.

[Dick Brown]

If you are running a wide stack, and if they are 8" blades, you have a lot of weight in them that has to wind down. I would think they and the motor would try to slow down at near the same speed, but sounds like the motor, belts or arbor may be trying to stop faster than the blades and they are putting a forward spinning force on the nut which loosens it. Check for drag in motor and arbor bearings. Shoving a scrap wood into the blades as you hit the off switch will keep the nut tight but is not an answer to the problem.

[Dave Richards]

You aren't, by any chance stacking the chippers so their teeth are in contact or in contact with the teeth on the outer blades are you?

[Dave Zellers]

You aren't, by any chance stacking the chippers so their teeth are in contact or in contact with the teeth on the outer blades are you?
That's a good thought. The teeth overlap so it's really important that the chippers be staggered.

[george wilson]

Sounds like the motor is breaking the speed faster than the dado set can handle without continuing to spin too fast and loosen the nut. The dado (saw nut) can only tighten as you are cutting with it.

[Jamie Buxton]

Dunno about Freud dado blades, but Freud makes saw blades with a red Teflon coating. The slippery coating causes the symptom you're concerned about. I use a sander to clean off the area where the arbor nut contacts, and that solves the problem.

[Rick Potter]

As to the second part of your question. I don't know how old your Unisaw is, but mine is an '83, and it has a flat on the arbor for a second wrench.

Rick Potter

[thomas d evans]

You aren't, by any chance stacking the chippers so their teeth are in contact or in contact with the teeth on the outer blades are you?

+10
As Dave says or....
I just built a finger box joint jig and went through several setups of various sizes on my unisaw. I found that I had to be very attentive that all blades and shims were FULLY pushed flat with each other while tightening the stack. They had a tendency to hang up on the arbor threads.

[Joe Kieve]

You aren't, by any chance stacking the chippers so their teeth are in contact or in contact with the teeth on the outer blades are you?

Another thought along these lines...are you using the metal shims that come with many sets? Sometimes they will hang up on the arbor threads and not tight against the blades. You think everything is tight but it's not.

[Mel Fulks]

I think George's explanation is the most likely.The set I was using was a nice 10 inch FORREST set that would cut a whole inch .Since the jobs did get done they must have loosened just when the machine was slowing down. If that is the case just feed in a scrap piece as you turn it off.