Table Saw Won't Make Square Skim Cuts

[Bill Healy]

I am trying to tune up a Craftsman hybrid table saw. I can make a square cut so long as the full width of the blade is engaged in the workpiece. However, if I try to take a skim cut where the workpiece contacts only a portion of the blade, the cut will not be square. In a 6" board, it will taper to the left about 1/64th of an inch when viewed from the side of the board that rested up against the miter fence. I have tried to rule out error on my part by setting a stop on my miter fence (Incra 1000) to be sure that I am not somehow allowing the board to slip. I tried a new blade and achieved the same results as with the old one. There is nothing obviously loose in the trunnion assembly although I have not yet taken the top off of the saw to re-torque every bolt. Has anyone else encountered this problem and if so, what did you do to cure it?

[glenn bradley]

If I am understanding correctly, when you shave a bit off the end or edge of a board is when the deviation occurs. My immediate thought is a dull blade. This is a bit more impactive if the blade is also thin kerf. I used to run a Craftsman 22124 with thin kerf blades and had no problems with a clean sharp blade. A sub-optimal condition blade would exhibit misbehavior faster on a thin kerf than on a full kerf blade.

[Matt Day]

What type of blade are you using?

I know that RAS's can't do skim cuts well because of blade flex, which I bet could be the same for TS's. Maybe a full kerf blade and/or blade stabilizers would help. .

[Larry Edgerton]

Thicker blade. Thin kerf deflect too much. I think they waste more wood than they save.

Larry

[Lee Schierer]

If you don't own a dial indicator, go to Harbor Freight and buy one for $10. Then mount it to a block of wood attached to your miter gauge. Check your saw for alignment and for looseness in the blade. Once you have this set up, put the dial indicator in contact with the blade then wiggle the miter gauge in the slot left to right to see how much movement you get. With the indicator in contact with the front edge of the blade and the throat plate removed wiggle the arbor nut and see how much movement you observe on the dial indicator. These readings will help yo identify where your problem is, plus you will be able to precisely align your blade to the miter slot.

[lowell holmes]

Thicker blade. Thin kerf deflect too much. I think they waste more wood than they save.

Larry

My experience with a thin kerf Woodworker II belies this advice. It makes glue joint quality rip cuts period. I'm running a Delta 2000 contractors saw. It has no measurable run out.
I do have blade stabilizers on the saw. I get the same result with a Tenryu as well. The Tenyru is sharpened by Forrest.

[Art Mann]

Thicker blade. Thin kerf deflect too much. I think they waste more wood than they save.

Larry

I have not heard of anyone advocating the use of thin kerf blades just because they save wood. The reason I use a thin kerf blade is it allows my 1.5 hp saw to cut much more like a 3 hp saw. I can push 6/4 white oak through my glue line rip blade about as fast as I have any desire to push and the cut quality is as good as any other glue line rip blade I have ever used. When I upgrade to a cabinet saw, I may go back to full kerf blades but not before then because I can see no real advantage and one huge disadvantage - performance loss.

I think it is a long shot that the original poster is having problems just because of a thin kerf blade.

[Ken Fitzgerald]

Two things come to mind with these symptoms:

1. The thin kerf blade is deflecting or....

2. The bearings in the arbor are allowing the blade to wobble when both sides of the blade isn't supported by wood that has been cut.

[Alan Schwabacher]

It sounds like either the blade is deflecting, which could lead to a taper where the top is cut away less than the bottom, or that the stock is moving away from the blade during the cut, which could make a taper mostly front to back, but also up and down a bit because of the shape of the blade.

You can distinguish these by clamping the stock to the miter gauge and making a cut. After the cut, run the stock past the blade a few more times and listen. If the blade deflected, you should hear it continue to cut as you pass the stock by the blade again, but the sound will go away as the material being cut does. Once that happens, you should have a square cut.

If the stock has moved away from the blade, subsequent passes will not cut, and should sound similarly quiet. The clamping test and stop block you tried already should have prevented stock from being forced away from the cut, but it's possible slop in the miter gauge made a difference. Holding the gauge to one side as you cut, and then the other side and listening as you recut, should diagnose that.

[Jon McElwain]

A freshly sharpened blade will solve all manner of evils.

[Bill Healy]

Thank you to all who commented. Since I knew the miter gauge was tight in its slot (it is one of the Incra with the adjustable wedges for width) and was getting the same behavior with a new fresh out of the box 0.125" Freud ATB industrial blade and a similar older 40 blade, I tried checking miter slot to blade alignment again. While I would have sworn it was good when I posted, I found it to be off about .003 to .004 inches. Resolving that has significantly helped the taper problem with skim cuts. I'm still not getting as straight a cut as I would like (now it is square in general but a little dished in the center), I can at least move on to chasing other problems!

[Michael Kellough]

Thank you to all who commented. Since I knew the miter gauge was tight in its slot (it is one of the Incra with the adjustable wedges for width) and was getting the same behavior with a new fresh out of the box 0.125" Freud ATB industrial blade and a similar older 40 blade, I tried checking miter slot to blade alignment again. While I would have sworn it was good when I posted, I found it to be off about .003 to .004 inches. Resolving that has significantly helped the taper problem with skim cuts. I'm still not getting as straight a cut as I would like (now it is square in general but a little dished in the center), I can at least move on to chasing other problems!

Looks like you found the source of the problem. I just want to add that you get the same unsquare result when there is too much clearance between the fence and the rear of the blade.

Some people like to angle the rear of the fence away from the blade. There may be some benefit to that but if the shift is too much you'll get noticeable differences in the cut bevel depending on the projection of the blade.

If the bevel gauge was set to 90 degrees while the blade is at full projection then the the cut bevel will be more than 90 when the blade projection is less. With experience you can set the bevel gauge to less than 90 to compensate.

The reason being that the blade is round, moving the wood past it at any angle other than dead parallel results in the wood being undercut (overcut on the bottom).