Table Saw - not 90 degrees after lowering blade
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Alan thanks for all the help. Let me see if I can explain this more clearly. I can raise the blade up a little, check it and it's less than .001" out from front to back. I'm using the same tooth during the test. I then raise the blade another 1/4" and repeat test, same tooth or a different one it doesn't matter I still get less than .001". Let's assume I stop with the blade all the way up. I'm happy everything is near perfect etc.
Now lower the blade 1/4" and repeat the test. Now I get .005 or 006" out front to back ( not home and can't remember exactly but it way off). Now move down another 1/4" and it's still .005" off. Repeat two or three more times with the same results.
Move blade 1/4" up from where ever you did the last test and do the test and now I'm back to .001". A lot of people have commented (on mutilple sites) that it's back lash. I do have about 3/4" of play when I turn the handle that nothing moves except the handle but I don't know if that matters.
I'm going to call jet tomorrow if I get a chance but I'm out of town until Thursday so I can test anything
Steve
Now lower the blade 1/4" and repeat the test. Now I get .005 or 006" out front to back ( not home and can't remember exactly but it way off). Now move down another 1/4" and it's still .005" off. Repeat two or three more times with the same results.
Move blade 1/4" up from where ever you did the last test and do the test and now I'm back to .001". A lot of people have commented (on mutilple sites) that it's back lash. I do have about 3/4" of play when I turn the handle that nothing moves except the handle but I don't know if that matters.
I'm going to call jet tomorrow if I get a chance but I'm out of town until Thursday so I can test anything
Steve
We are on the same page now. I agree, it is a form of backlash, but as I understand it, it is perpendicular to the plane of the blade and direction of movement of the blade. It may be that whatever rides in whatever groove or slot is cocked or forced one way (apex to the right and bottom of the blade to the left) when the blade is driven up, but when it is lowered the mechanism and hence the disk of the blade are cocked in the opposite direction.
I has been so long since I assembled my saw after removing the top and lifting it up to my shop I don't remember what the whole trunnion details look like anymore. But sounds like you have definite slop there. I don't know if I have ever heard of an adjustment for that.
The measurement change could happen with a tilted blade/arbor if the arbor that can move axially in the bearings. I don't think that is the problem because there is no reason for axial motion of the arbor with only the height of the blade being changed.
Did you watch the blade tilt when adjusting the height? Even though you are only adjusting the height, if the tilt mechanism has slop it could be tilting on you without you noticing. You would need a Wixey or other tilt box.
I'm about out of ideas without tearing into my saw to give the trunnion a close look.
Here is a situation I found on the web that would cause your problem:
"Here's the latest update. I took the saw apart and I found that there was
significant play in the arbor assembly. Not the arbor or arbor bearings,
but in the hinge that attaches the arbor flange to the trunnion. When I
apply light pressure to the blade I can clearly see the flange move. The
saw is going back to Grizzly next week. Hopefully, they will be able to
fix it, or exchange the saw."
I has been so long since I assembled my saw after removing the top and lifting it up to my shop I don't remember what the whole trunnion details look like anymore. But sounds like you have definite slop there. I don't know if I have ever heard of an adjustment for that.
The measurement change could happen with a tilted blade/arbor if the arbor that can move axially in the bearings. I don't think that is the problem because there is no reason for axial motion of the arbor with only the height of the blade being changed.
Did you watch the blade tilt when adjusting the height? Even though you are only adjusting the height, if the tilt mechanism has slop it could be tilting on you without you noticing. You would need a Wixey or other tilt box.
I'm about out of ideas without tearing into my saw to give the trunnion a close look.
Here is a situation I found on the web that would cause your problem:
"Here's the latest update. I took the saw apart and I found that there was
significant play in the arbor assembly. Not the arbor or arbor bearings,
but in the hinge that attaches the arbor flange to the trunnion. When I
apply light pressure to the blade I can clearly see the flange move. The
saw is going back to Grizzly next week. Hopefully, they will be able to
fix it, or exchange the saw."
Precisely the situation I had in mind. One of the shaft journals is probably ever so slightly out of round, or the pivot shaft ("hinge pin") has a defect in it where it passes through the shaft holes.
C.
Talked jet. They said there is an adjustment for the slop in the gears but that would probably not fix it. He said it was likely a loose bolt or a cracked trunnion. Unfortunately that will mean a complete teardown...I think if it comes to that all ask for a replacement or see if they'll do it. My time in the shop is already very limited. As it is I have to take the top off just to see if things are broken or loose
With a helper you will likely be able to unbolt the table (typically 4 bolts, one per corner) and carry and rest the entire table, including rails, on your workbench while you inspect the trunion (just be sure to remove the fence first so that it doesn't slide about while you move it). This will save you a fair bit of assembly time when it comes to re-installing the table later on.
You will want to remove the ZCI and blade first so that you don't damage the blade -- and you will have to cut a new ZCI when you reassemble since you will likely not duplicate the original alignment perfectly. Then the blade to miter slot and fence to blade (as well as measurement site) will all need to be readjusted when you re-install the table. The only 'hard' adjustment is getting the miter slots parallel to the blade once again, and that is accomplished by pivoting the table about one bolt (fully loosen other 3) with a mallet. You may also need to reset the 45deg and 90deg stops depending upon whether the trunion's stops are referenced against the table or the trunion/cabinet assembly.
From there, with the help of a good flashlight (and possibly magnifier), you should be in a good position to see where the movement is coming from. If you have a magnetic base for your dial indicator you can also use it to measure for lash/play by securing it to the saw chasis or other suitable reference point. While you are in there it is an excellent opportunity to fully clean the trunion assembly and fully relubricate with paste wax or silicone grease (or other dust resistant lubricant).
I'm guessing you already know most -- if not all -- of this, but it is information that others may find helpful in the future as well so I thought it worth mentioning.
Good luck!
You will want to remove the ZCI and blade first so that you don't damage the blade -- and you will have to cut a new ZCI when you reassemble since you will likely not duplicate the original alignment perfectly. Then the blade to miter slot and fence to blade (as well as measurement site) will all need to be readjusted when you re-install the table. The only 'hard' adjustment is getting the miter slots parallel to the blade once again, and that is accomplished by pivoting the table about one bolt (fully loosen other 3) with a mallet. You may also need to reset the 45deg and 90deg stops depending upon whether the trunion's stops are referenced against the table or the trunion/cabinet assembly.
From there, with the help of a good flashlight (and possibly magnifier), you should be in a good position to see where the movement is coming from. If you have a magnetic base for your dial indicator you can also use it to measure for lash/play by securing it to the saw chasis or other suitable reference point. While you are in there it is an excellent opportunity to fully clean the trunion assembly and fully relubricate with paste wax or silicone grease (or other dust resistant lubricant).
I'm guessing you already know most -- if not all -- of this, but it is information that others may find helpful in the future as well so I thought it worth mentioning.
Good luck!
Well I haven't taken the top off because I've been able to get to a bunch of bolts, and a lot were loose including at least 3 of the trunnion bolts and 1 of the motor mounts so I've tightened them all up but nothings has changed. I also ran these tests without the belt attched in case it was too tight but it didn't change the results.
I did get my magnetic dial indicator mount so I mounted to the bottom of the cabinet and put the dial indicator under the shaft (part number 144 - http://www.ereplacementparts.com/jet-xacta-708674-super-deluxe-saw-parts-c-32652_32759_33056.html). I mounted it on both ends and it really doesn't move - .001 - .002 at the most. but when I mount it just in front of part 146, the worm gear, and lower the blade, the shaft raises .007 which is the amount that I see the blade moving. Its not out of round it just raises .007 and stays there no matter how much I lower the blade. If I then raise the blade, it goes back to zero and stays there no matter how high I raise the blade.
Any thoughts :help:??? :BangHead::BangHead::BangHead:
Thanks!
Steve
I did get my magnetic dial indicator mount so I mounted to the bottom of the cabinet and put the dial indicator under the shaft (part number 144 - http://www.ereplacementparts.com/jet-xacta-708674-super-deluxe-saw-parts-c-32652_32759_33056.html). I mounted it on both ends and it really doesn't move - .001 - .002 at the most. but when I mount it just in front of part 146, the worm gear, and lower the blade, the shaft raises .007 which is the amount that I see the blade moving. Its not out of round it just raises .007 and stays there no matter how much I lower the blade. If I then raise the blade, it goes back to zero and stays there no matter how high I raise the blade.
Any thoughts :help:??? :BangHead::BangHead::BangHead:
Thanks!
Steve
Sounds like time to use an RA# !
If I am following your description properly, it sounds like you need to check parts #B-140 (bushing, 2 sets) for excessive wear/runout and a snug fit. There are two of these bushings and these serve the purpose of a low-friction (if properly lubricated) bearing surface for part #B-146 (the worm drive). You will also want to make certain that there is no loss of diameter in part #B-146 [shaft] where it revolves within the bushing.
You might also wish to check out parts B-138 [fiber washer] and B-143 [collar] of the other shaft and worm drive assembly, which adjusts blade angle, to ensure that neither of the fiber washers have worn/disintegrated or the shaft collar slipped -- just make sure everything is snug with no free play.
Your problem may still lie elsewhere, but this should be checked and eliminated first. Basically you have some lash/free play within your assembly that is compensated for when you raise the blade (likely courtesy of either gravity or friction in a pivot point), but which is not compensated for when lowering. It is just a matter of identifying where the movement is occurring and what is allowing for that unwanted movement -- something is out of spec.
Good luck!
I've checked all these parts and don't see anything wrong with any of that. I didn't disassemble it to check the diameter inside the bushings because, frankly that's too much work for a new saw.
I think I know what's wrong with it but I haven't figured a way to fix it. I believe there is too much play between the actual gears on the worm drive and on the arbor bracket. I believe what happens when I move the blade up, the worm drive will engage the arbor bracket teeth, take its weight and deflect the worm drive shaft downwards. Once all the weight is on the worm drive it remains true.
When I then lower the blade, there is a small amount of slop between the gear on the worm drive and the teeth on the arbor bracket. The slop can actually be seen as the worm gear moves from engaging on the back side of the the arbor bracket teeth to the front of the arbor bracket teeth. Its very small but you can watch the dial indicator move when this happens. The worm gear shaft lifts up, I assume because there is no weight on it. I'd say that all the weight at this point is being held by the trunnions and therefore there is no deflection in the shaft. Not sure if the slop has anything to do with it but it seems to move as the gear is moving between the front and back of the teeth.
Any ideas on how to correct it?
Steve
I think I know what's wrong with it but I haven't figured a way to fix it. I believe there is too much play between the actual gears on the worm drive and on the arbor bracket. I believe what happens when I move the blade up, the worm drive will engage the arbor bracket teeth, take its weight and deflect the worm drive shaft downwards. Once all the weight is on the worm drive it remains true.
When I then lower the blade, there is a small amount of slop between the gear on the worm drive and the teeth on the arbor bracket. The slop can actually be seen as the worm gear moves from engaging on the back side of the the arbor bracket teeth to the front of the arbor bracket teeth. Its very small but you can watch the dial indicator move when this happens. The worm gear shaft lifts up, I assume because there is no weight on it. I'd say that all the weight at this point is being held by the trunnions and therefore there is no deflection in the shaft. Not sure if the slop has anything to do with it but it seems to move as the gear is moving between the front and back of the teeth.
Any ideas on how to correct it?
Steve
I don't know if there is any adjustment for that or not -- some things are much harder to discern from a parts diagram then a good look at the real thing.
At this point, if you are relatively confident that this is the source of your troubl, call Jet and ask them if there is an adjustment for this (eccentric bushing/cam at the pivot point?). If not, with your saw still under warranty I'd just ask Jet to ship you a complete replacement trunion assembly (the *entire* assembly) so that all you have to do is unbolt the existing trunion and bolt in the new, then re-install your table and re-align everything. This should be much easier for you than dealing with shipping and packaging the entire tablesaw and it will save Jet a small fortune in shipping fees (if they want the old trunion returned, insist they pay return shipping). As such, it should not be too hard to convince Jet to go this route (famous last words, but this approach usually works for me).
Just my $0.02.
At this point, if you are relatively confident that this is the source of your troubl, call Jet and ask them if there is an adjustment for this (eccentric bushing/cam at the pivot point?). If not, with your saw still under warranty I'd just ask Jet to ship you a complete replacement trunion assembly (the *entire* assembly) so that all you have to do is unbolt the existing trunion and bolt in the new, then re-install your table and re-align everything. This should be much easier for you than dealing with shipping and packaging the entire tablesaw and it will save Jet a small fortune in shipping fees (if they want the old trunion returned, insist they pay return shipping). As such, it should not be too hard to convince Jet to go this route (famous last words, but this approach usually works for me).
Just my $0.02.
All Jet should need to replace is the trunion mechanism (a bolt-on assembly). If they are replacing the entire saw it is my hope that they intend to handle the delivery, re-packaging, and return shipping themselves. I certainly would not wish to to repackage an entire tablesaw for shipping myself!
Well the new saw showed up today along with a twin. For some reason they sent me two. They'd probably never know but I'll send it back. Anyway, its put together, turned up and NOT exhibiting the same problem as the other one so I'm happy. Everything rides up and down with very little deviance - I'd call it .0015". Thats certainly better than .010"!
Old one is boxed up and ready to go - along with its twin!
Steve
Old one is boxed up and ready to go - along with its twin!
Steve
Maybe the second one is for your troubles lol.Naw, but congrats on the new one being acceptable.
Tony
Tony
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