tablesaw bevel angle error

[Michael Panis]

Hi Folks,

I'm seeing a problem with my tablesaw (Jet cabinet saw) that I cannot explain.

First, I'll say my tablesaw top is flat and the workpiece I'm cutting is flat. I've adjusted the blade's tilt with an engineering square such that the blade, relative to the table, is dead on 90 degrees. The square rests directly on the blade, not the teeth.

After making a cut, I notice a small gap at the bottom of the workpiece, as shown in the diagram below:
tablesaw angle issue.jpg
If I put a square against the cut edge and look at the gap along the 6" edge, the gap is about 1/32", which is about 0.3 deg off of 90 deg. Since I'm using this edge as a reference for boring a hole that extends 6", I can't live with that variation.

Also, if I simply rest the piece against the blade after making a cut, I can see a small gap at the bottom.
And, if put both the workpiece and the engineering square used to setup the blade on the table, with the square against the cut edge, I can see the gap.

In short, the angle of the cut does not match the angle of the blade.

I've checked the arbor runout. It is zero. Shockingly zero. I'm impressed every time I've done that.
I've checked the flange that the blade sits against. It's runout is also zero.
The blade itself, a Forest Woodworker II small kerf, has about 5-10 mil variation across its surface, but I don't think that's the problem because:
a) I made the same cut with another blade and got the same result
b) Even if the surface of the blade has some variation, that doesn't mean the teeth have the same variation
c) Even if the teeth have some variation, I would expect that to cause some wobble or a messy cut, but not an incorrect angle. And the cut is clean.

Any ideas?

---Mike

[John Coloccia]

Are you ripping or cross cutting? Anyhow, check that the blade is square to the miter slot. If the blade is angled, it will cut an angle. Any angle will make a mini cove cut.

[John Coloccia]

Oh, and make sure you ZCI is level with the table and not causing a bump you can pivot on.

[phil harold]

Have you Checked all Adjustments?
http://www.woodmagazine.com/wood/pdf...ds-038free.pdf

Without actually looking at the saw I am thinking the blade is not parallel to the mitre slot
Go over all adjustments and then make a test cut again
good luck!

[Michael Panis]

It is a crosscut using an Incra mitre guage. Good point about the mitre slot alignment. I've checked it before, but not recently. Thanks!
(And I did make sure the Zero clearance insert is not interfering)

[Bill Huber]

Phil, I don't see that the blade being parallel with the miter slot should have anything to do with it, if you were cutting a 45 degree cut the face to the edge should still be 90 degrees, could you give some more detail on that?

I had somewhat the same problem at one time, I was checking the blade with an 18" drafting square and things were just fine. The problem was my extension on the left side was high on the left edge. So with a long board things were fine but with something short it was not cutting square. I readjusted the extension and now both long and short are square.

[John Coloccia]

Phil, I don't see that the blade being parallel with the miter slot should have anything to do with it, if you were cutting a 45 degree cut the face to the edge should still be 90 degrees, could you give some more detail on that?

I had somewhat the same problem at one time, I was checking the blade with an 18" drafting square and things were just fine. The problem was my extension on the left side was high on the left edge. So with a long board things were fine but with something short it was not cutting square. I readjusted the extension and now both long and short are square.

Imagine the blade 90 degrees to the miter slot. You will get a 10" radius on the cut. As it approaches parallel to the slot, the cut becomes straight. The path the wood takes needs to be aligned with the blade.

[Lee Schierer]

Imagine the blade 90 degrees to the miter slot. You will get a 10" radius on the cut. As it approaches parallel to the slot, the cut becomes straight. The path the wood takes needs to be aligned with the blade.

Nicely described. I agree check the blade alignment to the miter slot. Then don't forget to align the fence once the blade is aligned to the slot.

[Dick Brown]

Make a cut on a disposable piece of wood with a fair amount of wood both sides of the cut, slide the cut edges together with them on a flat surface and see if there is a gap at the bottom. If there is no gap, your blade isn't @ 90 degrees.

[phil harold]

The path the wood takes needs to be aligned with the blade.

If you are sawing a dado 1/8 x 1/2 deep if the fence is parallel you get a groove an 1/8"
If the fence is 15 degrees out of whack with the saw blade you get a cove 1.25 inches wide by .5 inches deep
His 1/32" is either the back or front of the blade cutting a small arc
@ 1/32" it looks more straight than an arc


When having cutting problems with equipment always make sure all your alignment is correct in all directions, once set they rarely go out of adjustment,
then look for other problems warped boards, table extensions not flat, warped cast iron...

[bob hertle]

Imagine the blade 90 degrees to the miter slot. You will get a 10" radius on the cut. As it approaches parallel to the slot, the cut becomes straight. The path the wood takes needs to be aligned with the blade.

I believe that would be a 5" radius! (Unless OP has a 20" saw)

Bob

[joe milana]

xxxxxxxxxx

[Bill Huber]

Imagine the blade 90 degrees to the miter slot. You will get a 10" radius on the cut. As it approaches parallel to the slot, the cut becomes straight. The path the wood takes needs to be aligned with the blade.

I am not saying you are wrong, I just can't see it. If the slot is not parallel to the blade the wood would go into the back of the blade as you made the cut or away from the blade as you made the cut.

If you are just cutting on the front teeth of the blade and those teeth are at a 90 degree angle to the table the face to end should still be at 90 degrees. The angle of the cut along the face will be off but the face to the end will still be at 90 degrees, how will that change, I just can't see it yet.

[John Coloccia]

I am not saying you are wrong, I just can't see it. If the slot is not parallel to the blade the wood would go into the back of the blade as you made the cut or away from the blade as you made the cut.

If you are just cutting on the front teeth of the blade and those teeth are at a 90 degree angle to the table the face to end should still be at 90 degrees. The angle of the cut along the face will be off but the face to the end will still be at 90 degrees, how will that change, I just can't see it yet.

The teeth don't move straight. They move in an arc (5" radius, of course, not 10" like I originally said...thanks Bob ). The profile left on the piece of wood that is cut is the 2d projection of the blade on a plane perpendicular to the direction the wood is moving. So as an example, put a piece of cardboard as a movie screen at the back of the table saw. Shine a light on the blade, and you get a straight, vertical line on the cardboard. That's the profile it will cut. Now twist the trunion so that the blade is crooked....say, it's heeled in at 10 degrees. It won't be a straight line anymore. It will be a gentle arc. At the extreme of 90 degrees, you will get a 5" radius circle, and that's what will be cut into the edge of the board.

Over a short distance, like 3/4" for example, a small misalignment won't look like an arc. Over a short distance, it will simply look as though the blade is tilted a bit.

[Bob Wingard]

If the blade is not parallel to the slot, what you can get is a mini version of a cove cut ... while it is conceivable, I would think the misalignment would be pretty obvious without need of any precision indicators.