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Table saw arbor nut loosening with dado stack

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Forum topic by unclearthur posted 05-12-2017 03:24 AM 7578 views 0 times favorited 85 replies Add to Favorites Watch
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unclearthur

78 posts in 1426 days


05-12-2017 03:24 AM

I’ve had a couple of strange experiences with my TS; hopefully someone can enlighten me on whats going on.

I recently bought a Grizzly 0690 tablesaw. A few days ago I was using a dado stack on it, and at the end of the cut, after I turned the saw off, there was a plunk and the stack just freespun for a minute. The arbor nut had fallen completely off.

I had been using quite a wide stack with shims etc, and I assumed that I had setup something crooked or whatever.

Today, I was using the dado again, 1/2” dado (just two blades and 2 chippers). I double checked that it was all tight, chippers at 90 degrees, etc before tightening the arbor nut. Made a cut. Basically the same thing happened; the nut coming completely loose.

In both cases the cut was OK, but the nut came loose I guess when the saw was turned off and the blade brakes.

Its a freud dado stack which I’ve had for over 10 years. 5/8” arbor size.

I’ve not had any problems with the regular blade on the Grizzly. I also never had a problem using the dado stack on my old contractor saw (which was right tilt, if that matters).

The dado blades all look in OK shape, flat, not anything obviously wrong.

I must be doing something stupid, but I’m not sure what. Any thoughts appreciated.


85 replies so far

View LittleBlackDuck's profile

LittleBlackDuck

874 posts in 458 days


#1 posted 05-12-2017 03:49 AM

Hi unca’, not being an engineer but rather a cautious woodworker with still 10 fingers, I can only postulate a solution.

I will assume that the dado’s bore and arbor are compatible (I could only imagine that would unbalance the wheel’s rotation and exert undue forces), however, unless my dislexia has just cut in, I believe the rotation of the blade should have the tendency to tighten the nut rather than loosen it.

If you are confident that the blades (and shims if used) are properly seated and snug against each other put a scrap piece of timber on the saw and make a sacrificial cut. The go test the nut. If it is loose after just 1 cut I would put it down to a mounting issue or as you suggested “braking forces”. If you then tighten it and make another sacrificial cut and it’s loose again then maybe the “braking” may have some weight to it (no pun intended). If it is still tight and becomes loose after prolonged use I’m lost and can only suggest giving up woodworking and taking up knitting… just watch those sharp points… from a distance. Just kidding, I have no other suggestion other than regularly check the status of the nut and try to associate any obvious alteration to your previous activity. This may be a pain but well worth the effort to try to isolate the cause.

I have used many different types of dados and so far none has turned me into a dodo.

Good luck.

-- There's two ways to do things... My way or the right way.. LBD

View pintodeluxe's profile

pintodeluxe

5214 posts in 2451 days


#2 posted 05-12-2017 04:01 AM

Try using just the nut and not the washer when using the dado set. You should see arbor threads through the nut.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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clin

672 posts in 634 days


#3 posted 05-12-2017 04:16 AM



... unless my dislexia has just cut in, I believe the rotation of the blade should have the tendency to tighten the nut rather than loosen it.

- LittleBlackDuck


When the blade is cutting the forces are trying to tighten the nut. On the other hand, if the motor were to slow down fast (and you all keep mentioning a brake?), then the momentum of the blade would try to spin the blade and loosen the nut.

I’m not aware of any brake on a TS, but I’m no expert. My experience is the motor and blade take quite a long time to come to a stop.

I’m with pinto, I’m wondering if the nut is being threaded on far enough. While a 1/2” dado is not that large, the washers are usually really thick and in general I don’t think are used when using a dado stack.

-- Clin

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MrUnix

5216 posts in 1837 days


#4 posted 05-12-2017 04:34 AM

I’m not aware of any brake on a TS, but I’m no expert. My experience is the motor and blade take quite a long time to come to a stop.

I can spin the blade off my TS when powering down if I want (which I don’t!)... I just set the deacceleration time to a couple of seconds or less :)

AFAIK, that griz just has a pretty standard TEFC motor and there is no mechanical brake involved… although a lot of people hear the centrifugal switch closing down and mistake that noise as a brake. Depending on age, it may be slowing down faster than normal due to bearings, but they would have to be pretty bad to effect it enough to spin the blade off.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View unclearthur's profile

unclearthur

78 posts in 1426 days


#5 posted 05-12-2017 04:39 AM

In both cases the nut was definitely fully on the threads, as the arbor is long enough, even when using the arbor flange (washer). So I’m not sure why I wouldn’t want to use the arbor flange?

“Brake” may be poor terminology, but when I turn off the saw the blade comes to a full stop within 3-4 seconds; something is causing the deceleration, and that I guess exerts some counter-clockwise (ie loosening) force on the arbor flange/nut. But that would happen every time you turn the saw off ….. shouldn’t loosen the nut.

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Carloz

539 posts in 229 days


#6 posted 05-12-2017 04:58 AM


I’m not aware of any brake on a TS, but I’m no expert. My experience is the motor and blade take quite a long time to come to a stop.

I can spin the blade off my TS when powering down if I want (which I don t!)... I just set the deacceleration time to a couple of seconds or less :)

AFAIK, that griz just has a pretty standard TEFC motor and there is no mechanical brake involved… although a lot of people hear the centrifugal switch closing down and mistake that noise as a brake. Depending on age, it may be slowing down faster than normal due to bearings, but they would have to be pretty bad to effect it enough to spin the blade off.

Cheers,
Brad

- MrUnix


Never heard of mechanical brakes on induction motors although I asuume there are some somewhere. The common and cheap way to brake induction motor is by induction not friction.

View LittleBlackDuck's profile

LittleBlackDuck

874 posts in 458 days


#7 posted 05-12-2017 05:22 AM

WHOA GUYS, yank on the bridle, ease up on the spurs and rein in those hosses
Sorry for the confusion… That is why I put ”brake” in inverted commas… I was inferring to a braking effect through motor resistance against forces/motion in affect. If I didn’t quote all my references to brake I again apologise.

WoodN’ said blade brakes in his intro post and I just ”pit bulled” on that statement.

PS. Dog lovers and pit bull owners need not reply

-- There's two ways to do things... My way or the right way.. LBD

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knotscott

7611 posts in 3013 days


#8 posted 05-12-2017 09:32 AM

Check the tension of your belts….sounds like they might be too tight if the blade stops within 3-4 seconds of shut down.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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hairy

2480 posts in 3170 days


#9 posted 05-12-2017 11:33 AM

Did you buy the saw new? If someone over tightened the arbor nut, threads on the nut would strip, not the shaft.

-- stay thirsty my friends...

View bondogaposis's profile

bondogaposis

4263 posts in 1989 days


#10 posted 05-12-2017 12:37 PM

I have had that happen. It is because one or more of the shims has dropped into the threads and is preventing you from fully tightening the stack. It will feel like it is tight, but as soon as the stack starts moving the whole thing loosens up. It happens most when using those really thin shims, I try to avoid using them or replace them with playing cards which work just as well but don’t bind in the threads.

-- Bondo Gaposis

View ohtimberwolf's profile

ohtimberwolf

697 posts in 1990 days


#11 posted 05-12-2017 01:16 PM

Puzzling because it happened with and without shims.

-- Just a barn cat, now gone to cat heaven.

View Carloz's profile

Carloz

539 posts in 229 days


#12 posted 05-12-2017 02:00 PM

The direction of the threads assumes tightening as the blade rotates. If it loosens the only reason you did not install the blades and chippers correctly. After you put the stack on “shake it up” to ensure all surfaces are flat and tight against each other. Often chippers catch on the threads even if you do not use shims

View unclearthur's profile

unclearthur

78 posts in 1426 days


#13 posted 05-12-2017 04:38 PM



Check the tension of your belts….sounds like they might be too tight if the blade stops within 3-4 seconds of shut down.

- knotscott

That’s an interesting comment because I had a different issue with the saw: when I first got it, when I’d start it (especially the first time in a day) it would take several seconds to come up to full speed. I asked Grizzly about it (and sent them a video), and after checking that the start-up capacitor was OK they decided the belts were too loose. We tightened those as much as I could and the problem was still there. They then advised:

The saw would typically only start like your machine for a few reasons. First, the bearings in the motor and/or blade arbor are to too tight at cooler temperatures. The start capacitor is weak. Or, the belts being loose or slipping, which they are not based on the videos.

The capacitor looked to be in good condition, but there is a possibility that it is still defective. Providing the overload is not tripping during startup, what you are experiencing is likely to not be harmful to the saw. At this point, we would recommend monitoring the table saw as the weather gets warmer and let us know if you have any other issues.

Since then the start-up issue has got better (it has also got warmer here) but is still sometimes noticeable.

Here is a video I made today of starting / stopping. Anything look strange to you? Is the blade stopping faster than normal?

Could “tight bearings or arbor” be causing both problems? ie – slow startup and too abrupt stopping? If so, do you think that improves on its own over time or do I need to do something?

Thanks for any advice

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unclearthur

78 posts in 1426 days


#14 posted 05-12-2017 04:44 PM


Did you buy the saw new? If someone over tightened the arbor nut, threads on the nut would strip, not the shaft.

- hairy


The saw was bought new, and I think the threads look OK. The nut hasn’t come loose when using the regular blade.


I have had that happen. It is because one or more of the shims has dropped into the threads and is preventing you from fully tightening the stack. It will feel like it is tight, but as soon as the stack starts moving the whole thing loosens up. It happens most when using those really thin shims, I try to avoid using them or replace them with playing cards which work just as well but don t bind in the threads.

- bondogaposis


Thats what I thought as well, but it happened again when I was not using any shims.

View papadan's profile

papadan

2556 posts in 3006 days


#15 posted 05-12-2017 06:46 PM

UncleArthur, are you using any oil or grease in your dado stack? All parts should be clean and dry.

-- Artificial intelligence is no match for natural stupidity!

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