Tablesaw arbor nut comes loose - and I now know why

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Travis Porter

Travis
Corporate Member
I have a PM 66 Tablesaw with a zero clearance insert. One of the ones you buy premade. Occassionally now, the arbor nut will come loose when I turn the saw off. The first couple of times I thought maybe I didn't tighten the nut properly, but just this past time it did it and I know I tightened it. Any thoughts or suggestions as to why this is happening?
 

sapwood

Roger
Corporate Member
Re: Tablesaw arbor nut comes loose

Travis, I had the same problem on the Griz. Check the arbor threads for signs of wear. I ordered new shaft ($9) and bearings since shipping was biggest cost. Mike Davis and son Collin were kind enough to do the work for me, but I'm sure you are competent enough yourself. ;-)

Between problem and fix I just made sure to retighten nut each time I used the saw. Since the fix I've not had any problems :icon_thum

Here's a link to my thread that posed the same question. Lots of helpful answers/suggestions in it. :)

Roger
 
T

toolferone

Re: Tablesaw arbor nut comes loose

The only blades I ever have a problem coming loose are the Freud Teflon coated blades. I don't ever use 2 wrenches on noncoated blades, but I do on the coated ones. That's the only thing I can think of.
 

cpowell

New User
Chuck
Re: Tablesaw arbor nut comes loose

That sounds a little bit scary. 8-O

I snug slightly more than finger tight for a regular full kerf blade. I use a wood block and wrench for a dado stack (being careful not to overdo it). When I go to remove the blade the nut has tightened so that it requires a wood block and wrench.

Chuck
 

DIYGUY

Mark
User
Re: Tablesaw arbor nut comes loose

Before you go to the trouble of a new shaft you might want to try double-nutting it. If the threads are a problem usually the ones on the end aren't as in tough shape as they don't get much action. Just a thought ...
 

junquecol

Bruce
User
Re: Tablesaw arbor nut comes loose

The only blades I ever have a problem coming loose are the Freud Teflon coated blades. I don't ever use 2 wrenches on noncoated blades, but I do on the coated ones. That's the only thing I can think of.
Tom, I don't think Freud blades are teflon coated. Best I remember from meeting a TWA that Freud sales rep did a couple of years back, they are coated with a propierty type of coating. If arbor nut is coming loose, it is from inertia of blade. (This is a real problem on some Delta 14-16" RAS with the electric brake.) Check and clean arbor flanges. You might want to take some 400 grit sandpaper to them. If any residue from a coated blade is on them, then they are more likely to slip. This could include "mill oil" from a new or newly sharpened blade. Also bad bearings that don't let arbor spin down can cause this action. It could be either bearings in arbor, or motor.
 

Travis Porter

Travis
Corporate Member
Re: Tablesaw arbor nut comes loose

I am going to give cleaning the arbor, roughing up the flanges a try. I will check for run out as well. The zero clearance insert does rub slightly, but I wouldn't think it should loosen the arbor nut the way it does. When it does do it, it is one horrendous noise with the nut coming loose and the blade spinning. If I have to break down and buy an arbor and bearings I will as I want the thing to run right. If nothing else, who knows I might buy a 5/8 lock washer, but I couldn't use it some of the time with the stack dado blade.

I have used the Freud teflon coated (I think that is how they are advertised) in the past, but since installing a splitter I have exclusively been using a Forest WW II blade.
 

Toddler

New User
Todd
Re: Tablesaw arbor nut comes loose

Does the arbor have a separate nut, or is it actually threaded and acting as the nut? I'm assuming there's a separate nut if you can use a lock washer between the arbor and nut. As a temporary fix, double nutting seems safer since you can tighten the two nuts together and not need to crank down to make a lock washer useful. Seems safer if the blade ever binds.

Also, what is the thread size? I have some of those pseudo locking type nuts where some of the threads are plastic. I'm pretty sure they're too small since they're from my weigh lifting / squat cage and likely only 1/4 or 3/8" ID, but I can check. Might be 1/2". If they're the right size I'll drop one in the mail to you.

Todd
 

NCPete

New User
Pete Davio
Re: Tablesaw arbor nut comes loose

those are called 'aircraft nuts' I believe????
 

Gofor

Mark
Corporate Member
Re: Tablesaw arbor nut comes loose

I doubt you will find self-locking nuts of the correct threads per inch to fit the arbor. Most self-locking nuts are fine thread, and also have a maximum number of "re-uses" before they no longer lock (depending on the criticality of the part, for aircraft some are allowed only the initial use, and most are allowed only 3 re-uses, and that is with a torque limiting wrench to tighten them). They do make a locking nut that has the actual metal peened in on the back side, but that style will tear up the arbor shaft.
As for a second nut (jam nut), if the inner nut moves outward during the "locking" tighening of the jam nut, the blade will be loose.
If you think something may be dragging down the arbor/motor causing the blade inertia to be the culprit, you may want to blow out the motor with compressed air. Could be saw dust buildup causing the drag, which also is probably causing a lot of friction heat in the motor. I don't think its the ZCI, as that would still be putting tightening torque on the blade just like cutting a piece of wood.

JMTCW

Go:eusa_thin
 

Travis Porter

Travis
Corporate Member
Re: Tablesaw arbor nut comes loose

Go, I think you have made the most sense I have heard so far thinking about it.

When I tighten the blade, I do it towards the rear of the saw. The blade goes towards the front, so that should keep it tight. I think I said that right. I posted on another site and they commented on belts and between the two, I believe it may be one or both. I will blow the motor out first as that is the cheapest route.;-)
 

Travis Porter

Travis
Corporate Member
Re: Tablesaw arbor nut comes loose

Well I have pulled the motor cover off and blew out the motor real good with an air hose. Additionally, I pulled out the dial indicator and I have less than .001 of runout on the arbor. The threads on the arbor look good and both flanges of the washers or whatever you call them are clean, no play whatsoever. I got out the blade cleaner and cleaned the blade since I had it off as well. One thing I did notice is that it seems the belts have gotten a "memory" where they want to sit in one spot. I am going to contact Powermatic tech support to see what they say.
 

NCPete

New User
Pete Davio
Re: Tablesaw arbor nut comes loose

memory is typical of v-type belts. especially when it starts to turn cold (though frankly this isn't cold). something to consider would be those silly link-belt things, they don't take a set, which is actually a contributing factor to vibration. your v-belts will probably show much less set if you have run the saw for some time, as they run and warm up, they 'heal' a little.
 

Travis Porter

Travis
Corporate Member
Re: Tablesaw arbor nut comes loose

Powermatic has yet to respond. Since I have taken the ZCI out and used the standard insert, the nut has not come loose since. It seems odd though since the nut should be tightening itself instead of loosening. When you do shut the saw down, you can "hear" the belts where the memory has developed. I am going to go ahead and order a pair of belts since I haven't replaced them since I bought the saw 15 years ago.
 

NCPete

New User
Pete Davio
Re: Tablesaw arbor nut comes loose

may also try locking the ZCI down with another piece of wood, and then running the blade up through it again. maybe a clearance issue, especially if the one throatplate is working, and the ZCI not?
 

junquecol

Bruce
User
Re: Tablesaw arbor nut comes loose

:roll:Before replacing belts, "clock them". That means loosen motor, and move one belt 90 degrees from original position. Now both memory sets won't occur at same time over sheaves. I do this on my Uni sometimes, especially when the shop has been cold. Because it has three belts, I "clock" them, one 90 degrees one way and the other 90 degrees the other way. You can get belts from NAPA, Grainger, Dillon. Any car place that sells Gates belts will be able to do a cross refence to PM's #on belt. Just take on with you, and be sure to ask for a match ground set.
 

Grgramps

New User
Roy Hatch
Re: Tablesaw arbor nut comes loose

Travis, I notice it's been a week since your first post and I wonder if you've figured this out yet. I can't imagine the insert could have a negative effect on this. It seems to me that a dragging insert would have the same effect as cutting wood. Both would have the tendency to tighten the nut. I agree with those who believe the culprit is blade inertia. The question is why does the motor, pulleys, bearings and belts present enough drag when turning off the motor to loosen the nut?
Roy
 

NCPete

New User
Pete Davio
Re: Tablesaw arbor nut comes loose

Roy, you are probably right, I was 'thinking backwards' (?)

but, if he is not having a problem with the regular throat plate, what is going on?
 

Grgramps

New User
Roy Hatch
Re: Tablesaw arbor nut comes loose

Pete, I believe it was mentioned that the nut loosens only occasionally, so I think we've merely been distracted by the mention of the zero insert. Sort of like hearing hoof beats and looking for zebras?
Roy
 

NCPete

New User
Pete Davio
Re: Tablesaw arbor nut comes loose

Pete, I believe it was mentioned that the nut loosens only occasionally, so I think we've merely been distracted by the mention of the zero insert. Sort of like hearing hoof beats and looking for zebras?
Roy


What? Don't you? :rolf:



I like the analogy. :lol:
 
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