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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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?
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.
Something just doesn't look right there, aside from how the blade stops pretty quickly. Have you checked the flange and washer to see if they have burrs? Checked how much runnout there is on the arbor? When it's in the stopping motion it looks like there's a wobble. Maybe that's just a trick of the camera, but it did appear that way.
He said 1/2". He also said the nut was fully on the arbor. I agree, that too thick a stack can lead to too few threads of the nut on the arbor, but that doesn't seem to be the case here. Good suggestion, bu not the solution, I am afraid.
All clean and dry …... I even just tried brushing the arbor and nut with a brass brush but basically it all seems grease free as far as I can see.
Something just doesn t look right there, aside from how the blade stops pretty quickly. Have you checked the flange and washer to see if they have burrs? Checked how much runnout there is on the arbor? When it s in the stopping motion it looks like there s a wobble. Maybe that s just a trick of the camera, but it did appear that way.
No burrs. When I set the saw up I checked the runout and thought it was OK, don't remember exactly how much variation. Haven't re-checked. Your right about the "wobble" but I've never known how to interpret that…..........
The nut just came loose again, this time with the regular blade (not the dado set). Bit scary actually. So I'm really dumfounded …..how hard do you tighten your arbor nuts on these saws? I've always been told not to overtighten ….... and never once had a problem on my contractor (lower hp) saw.
Here's 3 pics of the arbor, flange and nut. Anyone see anything strange? Just to be sure, the way I have shown the nut and flange together in the last pic is how they go on the saw, right? Can't see any other sensible way.
I'd send that video to Grizzly's tech service and see what they have to say. It's a bit slow to start, and very quick to stop. Sounds a bit sloppy on startup too.
BTW, you and your saw deserve a better blade than what's on there.
Blade seems to be stopping much too quickly. The mass of a dado stack could easily unwind the nut by stopping that fast. The fact that just the blade alone is stopping so quickly indicates something is definitely not right. In fact, with a heavy dado stack, the run down should take a lot longer than with the regular blade.
I agree, stopping unusually fast. Dado stack has more mass and therefore more momentum, so as the arbor slows too quickly there is more nut-unscrewing-force (NUF). Buy the way I just invented that term.
I'm sure the TS experts here can elaborate on what is wrong. Though being new, it should be on Grizzly to sort this out for you.
I also heard quite a rumble when you started the saw. Maybe bearings are bad. I know it's new, but maybe somehow they got damaged. Your average worker is not going to admit to having dropped an assembly. "Still looks okay, still spins. I'll go ahead and put it in".
I know with my saw (not a Grizzly) I can brew a pot of coffee in the time it takes to come to a stop. Well, maybe not quite that long.
I agree with knotscott, send it to Grizzly, something is definitely not right with the slow start up and rapid deceleration when turned off. The motor, motor bearings, belts or arbor bearings are causing the excessively quick stop and the inertia carried be the blade(s) are loosening the nut as a result. It could be a combination of two or more of those problems. If I were attempting diagnosis independent of what Grizzly said, I would first remove the belts (after removing the blade) and see if the motor turns freely (with the saw unplugged) then check the arbor in the same way. Then turn the motor on to see how it behaves with no belts installed and note any differences. It almost seems like it has an issue switching from the start winding to the run winding or something is bound up. In the video I did notice the blade stops and the belts don't find their set on the pulleys at the very last blade rotation like virtually every other belt drive saw I've ever seen. The blade stops as if a disc caliper is applied and very little movement occurs especially the third stop.
If you put a blade on and tighten it and it won't spin with just a little pressure then something isn't right. And if it requires force then something is definitely wrong.
OK thanks everyone, I will contact Grizzly again and see what they say.
By the way, I tried one more time with the dado setup, being 1,000% careful on the setup, and the nut loosened again after one cut. Too dangerous! Not trying again.
Made another video for Grizzly as well, and you can hear quite a clunk a second or so after the saw is turned off. Probably not a good sign either.
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