Weird tablesaw cut problem

wormil · Apr 3, 2013

My 15 year old Delta contractor has developed a strange problem. Every so often when cutting through the middle of a board the blade will give a little wobble. It happens at regular intervals, maybe every 3 seconds. It's very obvious on my full kerf rip blade and it may be happening on my thin kerf combo blade but it's hard to tell.

If it is the blade, wouldn't it happen almost constantly? Unfortunately I don't have a dial indicator to check the blade but since it only happens once out of every couple hundred rotations it might be impossible to measure.

It's hard to describe and too subtle to photograph but you can hear it. Here is an exaggerated drawing to show what I mean. It might happen 3 times on a 4 foot cut.

Hammerthumb · Apr 3, 2013

Check your belts. Might need replacing. See if they have any glazed spots on them.

bondogaposis · Apr 3, 2013

Yeah, that was my thought too. Check the belt and pulley's. Make sure the pulley's are not slipping.

CharlieM1958 · Apr 3, 2013

My first thought would be arbor bearings, although I would not expect the problem to occur at such regular intervals.

Here is a discussion you might find helpful.

PurpLev · Apr 3, 2013

like the others suggested my first guess would be the belt.

if you can HEAR it - then take the belt off, and power up the saw and LISTEN. if you can still hear it then it's the motor shaft bearings or the motor winding. if you can't hear it then it's most likely the belt (or the blade arbor). try replacing the belt and see if it clears it.

Airspeed · Apr 3, 2013

Does it do it without cutting? Something is making the blade resonate, try a different blade, if it still does it you have a belt prob or the arbor is bad. I had this happen to my Unisaw, it turned out to be the nut, it was threaded crooked and putting more pressure on one side of the blade. My wife was helping me rip some long stock once and kept moving the boards to the side, it heated up the blade so much that it was ruined and did the same thing you describe, has your blade gotten hot recently?

Fettler · Apr 3, 2013

Do you hear the motor slowing when that happens? Could it be that the wobble happens when you hit a denser bit of wood (a shadow of a knot)? Is there any noticeable play in the arbor?

That sounds like a pain to diagnose.

ClintSearl · Apr 3, 2013

There's a bunion on the trunnion.

IrreverentJack · Apr 3, 2013

Have someone watch the motor to see if you have a bounce - If your belt is too short or slipping the motor pulley can walk up the belt when you have blade resistance then drop down. If you stop the cut, does it stop? -Jack

MarkDavisson · Apr 3, 2013

Clint gets the prize for comment of the day!

wormil · Apr 3, 2013

It only happens when cutting in the middle of a board, ripping or crosscut. When I say I can hear it, I mean I can hear the blade dig deeper into both side of the cut, sometimes causing a burn, everything else sounds normal. I cleaned the blade and checked all the extension tables for flush/level but it still happened.

It does not happen when: not cutting, cutting on the edge of a board, or taking light cuts. I inspected the belt recently and there is no fraying, hazing or bumps, it looks fine but I won't rule it out.

@PurpLev - Something is making the blade resonate

Yes, well put. Something is causing a momentary resonance when cutting inside a piece. I made a new zero clearance insert on the off chance that my factory insert (which I normally use with the rip blade) is bobbling and causing the wood to shift. I'm getting ready to go test it.

Grandpa · Apr 3, 2013

My first thought was heat. That is usually caused by a dull blade.
My second thought is a slipping belt or a slipping pulley.

JoeinGa · Apr 3, 2013

"@PurpLev - Something is making the blade resonate"

Yep, and I'm guessing it's HEAT. The deeper you cut into the wood, the hotter the blade gets. I think the heat is causing the blade to actually warp. And then as the blade slows it cools, making the blade stiffer again. Any chance you checked the blade for very small cracks? Heat would cause those to "open up", thereby pushing the blade out of true.

wormil · Apr 3, 2013

Heat would make sense except it was my first cut of the day, through 4' of 1/2" MDF so I can't imagine that was the problem. I installed a splitter hoping it would fix the problem but after switching to a new zero clearance insert and installing the splitter it only happened once in a 4' cut but it still happened. The blade isn't very used, freshly cleaned, is relatively sharp. I was just up under the saw yesterday and didn't see any problems. Tomorrow I'll switch to a full kerf combo blade and see if it still happens. If the other blades cut fine I'll send this one out for a sharpening/rebalancing.

CarpenterMark · Apr 3, 2013

I't's the result of an overfeed with a less than sharp blade; slow down the feed and see if it stops.

jumbojack · Apr 3, 2013

I am thinking a blade resharpen. You get the plus of a nice clean blade and I think it will cure your woes.

HR222 · Apr 3, 2013

You may have a blade spindle shaft bearing issue. Or possably a rear motor armature bearing.
This can cause weird blade runout as they load and unload. I hope I'm not being to technical, I'm not
familiar with your model but if your model is direct motor drove to the blade. then the magnetic field
in the motor can cause armature pulse when bearings [wheather bronze or roller] are worn.

distrbd · Apr 3, 2013

I would also suspect the blade being the problem,try another sharp blade ,if you eliminate the blade as the source then my next guess would be the arbor shaft,you may need to replace the bearing.

wormil · Apr 5, 2013

Okay, it's just that blade, it's not dull, and feed rate makes no difference. It also makes a very high pitch noise which I didn't notice yesterday wearing hearing protection. So I'm going to contact Freud and see what they suggest before I plunk down $10 for sharpening/balancing.

TopamaxSurvivor · Apr 5, 2013

My money is on a bearing starting to go.

History · Apr 5, 2013

I'd be suprised if it was a bearing, his saw looks too new. It's got to be something simple. Is there anything in the owners manual about it in the trouble shooting section ?

MattinCincy · Apr 5, 2013

I used to have the exact same problem with my last saw - a Jet Proshop. When I upgraded to my cabinet saw, the problem went away. I always attributed it to a lack of power.

History · Apr 5, 2013

Matt, a Cabinet table saw is not appropriate or even necessary for every shop. If you had a lack of power problem, it wasn't because of the saw. There are numerous things that it could of been. The saw not plugged into a sufficient electrical circuit and or extension cord, pulleys not aligned, not using the correct blade for the job, a dull blade, a fence that is out of parallel, the tilt hand wheel lock not tightened, etc. I bought a new Delta Contractor's table saw with a 30" Unifence almost 20 years ago, it's been a great saw for my shop.

SamuraiSaw · Apr 5, 2013

"If you had a lack of power problem, it wasn't because of the saw"

Talk about not having a clue…......

Have you ever used anything besides a contractor saw?

GROOVY56 · Apr 5, 2013

I would check the bearings,, thrust and radial play

TopamaxSurvivor · Apr 5, 2013

I have never seen that with my little 3/4 hp contractor saw.

Weird tablesaw cut problem

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