Odd vibration in saw blade.


Rick A McQuay

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I have a Freud LM72R010, 24T, 10", RIP blade. Every 2 or 3 seconds it gets a momentary wobble leaving a rough cut. Otherwise the blade cuts well and seems fairly sharp. Slowing the rate of feed doesn't help. None of my other blades do this. I tried calling Freud but no one answered, they might be closed so I sent them an email. A sharpening/balancing may cure it or or may not, I hate to spend the money to find out. Anyone experienced something like this?

 

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My experience with this kind of occilation is that there is rarely one impacting factor. Keep in mind much of my experience with cyclic occilations is with heavy machinery many years ago and not specifically a table saw. Your blade could be out of balance but the fact that it cycles makes me think it is syncing with a failing bearing, pulley, or belt. The cycle is the balance issue periodically syncing with the frequency of the play in a bearing in the situation I suggest. I'd go over the whole saw with care, change blades, and even try to find a way to check the balance on your Freud.

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Your explanation makes sense. So you think it might be happening with all the blades but is only noticeable with the full kerf rip. The saw is about 15 years old but has had only moderate use. I checked the belt recently and it looked fine but I'll replace it and see if that helps. 

 

Here's a thought... What if it's not a saw or blade problem but a power supply problem? When I shut the saw off it vibrates a little. The full kerf blade would take a little more oomph than the thin kerfs, if the power wasn't steady it could lose speed for a moment causing the vibration. 

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Again I'd suggest multiple factors. Your motor spins so fast that a motor issue shouldn't only affect operation every 2-3 seconds. In fact everything should change over multiple times in 2 seconds and that is what makes me think syncing wobbles. There are some electric motor guys in the forum who know much better than I.

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Have you checked the fence for parallelism lately?  If your other blades are thin kerf it could be they are able to flex but the full kerf is being asked to flex too much and it flexes a bit then snaps back and repeats.  I have experienced this phenomenom, and while my saw does have some vibration issues, especially when it's cold, it mainly happens with my 30T full kerf rip blade.  My fence leaves much to be desired so fence alignment is a constant headache. 

 

But on the other hand it tends to happen more with harder woods, so I don't know if it's just related to the saw not having enough power with the combination of full kerf and hard wood.  I've never really gotten to the bottom of it, but I just use dedicated thin kerf rip and crosscut blades now which avoids the issue.

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The blade may have lost its tension causing it to oscillate.  You might even try it on another saw to see if it still does it.  Not sure if resharpening would help with that if that's what's happening.  I'd speak to an experienced sharpener to see what they suggest.  $15 for a resharpening is pretty reasonable if it solves the problem, otherwise even a new 24T FTG full kerf blade isn't too expensive.  

 

Some bargains:

Delta 35-7642 full kerf 24T FTG (made in the US) $37.50 shipped

Bosch PRO1024RIPB 24T FTG full kerf ($22.50 shipped)

Delta 35-611 18T full kerf FTG (made in Germany by Leitz)  $33.50 shipped

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I'm thinking bearings....maybe someone can weigh in on this but on a car or truck, you can jack a tire off of the ground and

push/ pull the top of the tire and often discover play in a worn wheel bearing or tie rod end.  Can you maybe discover this in a table saw blade bearing also?

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The blade may have lost its tension causing it to oscillate.  You might even try it on another saw to see if it still does it.  Not sure if resharpening would help with that if that's what's happening.  I'd speak to an experienced sharpener to see what they suggest.  $15 for a resharpening is pretty reasonable if it solves the problem, otherwise even a new 24T FTG full kerf blade isn't too expensive.  

 

Some bargains:

Delta 35-7642 full kerf 24T FTG (made in the US) $37.50 shipped

Bosch PRO1024RIPB 24T FTG full kerf ($22.50 shipped)

Delta 35-611 18T full kerf FTG (made in Germany by Leitz)  $33.50 shipped

This would be my guess.

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knottscott, I'm not familiar with blades losing tension, can you explain? Thanks.

 

Tim, I've tried what you suggest about rocking the blade but there is no bearing play I can detect.

 

krt, it happens in all wood, hard, soft, ply, and mdf. I did check the fence for parallel.

 

I'm going to replace the belt today just to eliminate a variable.

 

It must be a bad blade. But it is counterintuitive that a bad blade would vibrate every 2-3 seconds instead of constantly.

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Saw blades tend to want to distort at high speed because the outer portion of the blade wants to stretch away from the center because it's spinning faster at the outside of the plate than the inside.  To compensate for this tendency, saw blade manufacturers "tension" the steel plate by placing it between two high pressure rollers that compress the steel...you can often see it as a circle around the blade between the hub and outer rim.   Some are hand hammered to tension them.  Sometimes heat can cause the blade to lose it's tension, and vibrate more or go into some unusual harmonic oscillation that occurs at a repeated frequency.  Some harmonics exist in all saw blades...modern blades have gotten much better at controlling those harmonics through better steel technology and better manufacturing techniques like tensioning and laser cut expansion slots, but the tendency still exists to some degree, and if the blade got hot or wasn't quite right when new, it can oscillate.   

 

See the light circle on the back of this Amana Tools combo blade and on this CMT GLR blade:

AmanaDWbladepics002.jpg CMT30back.jpg

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Your explanation makes sense. So you think it might be happening with all the blades but is only noticeable with the full kerf rip. The saw is about 15 years old but has had only moderate use. I checked the belt recently and it looked fine but I'll replace it and see if that helps. 

 

Here's a thought... What if it's not a saw or blade problem but a power supply problem? When I shut the saw off it vibrates a little. The full kerf blade would take a little more oomph than the thin kerfs, if the power wasn't steady it could lose speed for a moment causing the vibration. 

 

 

My experience with this kind of occilation is that there is rarely one impacting factor. Keep in mind much of my experience with cyclic occilations is with heavy machinery many years ago and not specifically a table saw. Your blade could be out of balance but the fact that it cycles makes me think it is syncing with a failing bearing, pulley, or belt. The cycle is the balance issue periodically syncing with the frequency of the play in a bearing in the situation I suggest. I'd go over the whole saw with care, change blades, and even try to find a way to check the balance on your Freud.

Seems that this is the first full kerf blade and that the wobble happens under load, I think would exacerbates the effect C Shaffer is pointing out.  Does that sound right, Shaffer?  

 

I love the diversity of knowledge on this forum!

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I'm really getting an education. Today I installed a link belt and the difference is incredible, like a new saw; much quieter and more smooth. But it didn't fix the blade issue entirely although it reduced it a lot. Before the wobble would happen about once in every 12" of cut, after the new belt it happened once in 12' of cutting. When I cleaned the blade I could only get the sides, the face of the teeth still have some pitch. Tomorrow I'll look for a brush with longer bristles that will let me get down in there and clean more thoroughly. I dread it, but maybe I need to pull the saw top and clean the inside very thoroughly.

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McQ, I just soak mine a bit in Simple Green Concentrated and then hit the teeth with a toothbrush or small brass brush.  I've found a water catch for a planter is perfect because it elevates the teeth.  I have one that fits both my 10 and 12 inch blades.

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That looks very handy Vic. I stay away from Simple Green as it reportedly will damage the carbide although they do make products that are supposed to be safe. My wife is a helicopter crew chief and they are not allowed to use Simple Green. WD-40 and PB Blaster, both worked fine but I still needed a brass brush to remove the pitch, a teflon coated pizza pan from Dollar Tree to hold the blade. Was going to use citric acid but wasn't sure if it would attack the blade's coating.

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http://www.carbideprocessors.com/pages/saw-blades/steel-saw-plate.html

I have always bought blades on severe budget and for external features made of cedar etc. tensioning is a new discussion for me so I am trying to do some homework. This article seems to call the of tensioning small blades (10" and under) questionable in value. As I have no experience with this particular aspect I admittedly did the dangerous and searched the web. I am curious how those of you with more experience respond to this.

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http://www.carbideprocessors.com/pages/saw-blades/steel-saw-plate.html

I have always bought blades on severe budget and for external features made of cedar etc. tensioning is a new discussion for me so I am trying to do some homework. This article seems to call the of tensioning small blades (10" and under) questionable in value. As I have no experience with this particular aspect I admittedly did the dangerous and searched the web. I am curious how those of you with more experience respond to this.

I had never heard of tensioning.  interesting article.  I've never had a saw plate distort or wander in the cut, even when I've used a thin kerf blade, like the Freud Diablo.

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Vic, I suspect that Simple Green is probably no danger unless blades soak in it for extended periods and even then I found a post elsewhere by someone who analyzes blade failures in their job and said that carbide technology has come a long way and cobalt leaching is no longer a concern. My blades are almost all Freuds and they recommend soaking overnight in Kerosene. 

 

I did find this interesting article, looks a bit dated but still useful. Carbide Processors tested and found generic oven cleaner to be the best but citrus cleaners were a close second and basically tied with brand name oven cleaners.

http://www.carbideprocessors.com/pages/saw-blades/cleaning-saw-blades.html

 

I'll try a citrus cleaner and use a scotchbrite pad, like Marc did in his video, to get between the teeth.

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Back on topic, before you invest in any more parts for the saw, I'd get some compressed air blown into the motor to remove dust buildup.  Even those with ducting in their saw cabinets can get some buildup, especially if this saw has been "lightly used" for over 5 years.

 

(I'd laugh if it's because a spider is doing a happy dance on the shaft while the blade is spinning.)  I'm inclined to agree with the balance issue, since you've switched to a link belt from a solid belt.  Those have been known to reduce excess balance issues.  I'd also worry that maybe the motor itself is slightly out of balance.  Check that all the bolts are tight before you do any work on it.  (And don't think that you can mount the blade back into the saw and turn it on to get those last few drops of cleaner from the blade!  -That's my trick!  :D )

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