tablesaw bevel angle error

[phil harold]

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.

If the front of the blade is closer to the slot then the middle
The bottom of the board will be shorter than the top

[Andrew Pitonyak]

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 don't have time to do the match now, but, at 90 degree cut with a 10" blade on 1.5" material would leave a different of about 0.23" from top to bottom.

I did not draw the picture or take the time to make sure that the difference is truely related to the sin of the angle, but, if so, then the sin(x) * .23 = 1/32. Solve for x. So x = arcsin(1/32/.23) = roughly 8 degrees. Again, I did not draw the pictures and verify the geometry, and it is certainly something to check, but I am more inclined to agree with Bill Huber that it is probably related to the saw top.

I am curious, what happens if you cut on the other side of the blade?

Also, if there is something with the table top, you should be able to see that when you simply set the piece of wood against the blade while the blade is not spinning. If you do not see the gap, then it may be something as simple as blade deflection.... but you saw this with multiple cuts.

[glenn bradley]

I'm in the camp that suspects material travel to blade to not be perpendicular. Getting a bit of a cove cut as a result.

[Michael Panis]

I was sold on the idea of the blade's not being aligned with the mitre slot, but measured it last night and it is aligned to within 0.001" so that does not appear to be the problem.
I did notice two things, though..
a) I had tightened the arbor nut with a wrench (I know...I know...hand-tighten only). Loosening it and tightening it by hand seemed to decrease the problem. I believe that what was happening was that the excessive force put a slight dish in the blade. This means that when the arbor was exactly parallel to the table top, the dish caused the top of the blade to be closer to the left of the blade. Since you align the surface of the blade to the top, to get the dished surface as close as possible to the edge of the engineering square, I had to tilt the top of the blade to the right. The teeth, however, only travel around the circumference of the blade. By aligning the dished surface to the table top, I had misaligned the teeth such that the teeth at the top of the blade were closer to the right while those near the table stop were closer the workpiece.

Furthermore, when I put a new blade on the saw, I didn't re-align it, so it produced the exact same bevel error!

b) Even though I aligned the blade to the tabletop with the zero clearance insert removed, I believe there may have been spots on the ZCI that were slightly higher, almost imperceptibly, than the table. This might have added to the problem, although to a smaller degree.

I still have a little more alignment and testing to do...

Thanks for all the suggestions...

---Mike

[Jay Maiers]

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)

Does this mean that it only happens when you are using the mitre gauge, and not when you use the fence?

Does it happen with both miter slots, or just one of them?

Is it possible that the motor torque is pullng the saw out of square while it's running?

Have you checked to make sure the Incra is really at 90 degrees? (I don't think this one matters, but one never really knows...)

[Alan Schwabacher]

Have you made check suggested earlier in the thread, to put the two cut parts back together on a flat surface and check to see if they meet? This will distinguish between a tilted but flat cut from a tilted blade, (if the pieces meet top to bottom) and a wedge shaped cut (pieces meet at top but not on bottom) that would result from a misaligned movement of stock. Note that stock movement can be misaligned either if the blade is out of parallel with the miter slot, or if the stock shifts on the miter gauge as you cut. Sandpaper on the miter gauge fence prevents stock shifting.

[Myk Rian]

Not only should the blade be parallel with the miter slot, so should the fence.

[Steve Baumgartner]

Despite the theoretical appeal of coving due to misalignement to miter slot, I don't think that is a credible explanation. Think about it: the depth of the cove is equal or less than the difference between the distance between the blade and miter slot where the teeth pass through the table surface vs at the center of the blade (equal if the blade height is exactly the thickness of the wood). A 1/32 cove would mean at least a 1/32 skew, which would mean a 1/16 difference between front and back of blade!! If his saw was that far out, there would be other problems such as burning and massive chipping at the back side of the cut.

Something else, such as the suspected cupping due to overtightening is going on.

While thinking about this, the following strange idea crossed my mind: the coving is away from the blade at the bottom on both the miter gauge side (cut by the front of the blade) and the offcut side (cut by the back of the blade). The angles are the same instead of complementary! That means if you do the traditional cut-an-flip test, it will look like you are cutting perfectly at 90 degrees despite the cove!
Steve

[glenn bradley]

I was sold on the idea of the blade's not being aligned with the mitre slot, but measured it last night and it is aligned to within 0.001" so that does not appear to be the problem.

Oh darn. That was my vest guess ;-)

a) I had tightened the arbor nut with a wrench (I know...I know...hand-tighten only). Loosening it and tightening it by hand seemed to decrease the problem. I believe that what was happening was that the excessive force put a slight dish in the blade. This means that when the arbor was exactly parallel to the table top, the dish caused the top of the blade to be closer to the left of the blade. Since you align the surface of the blade to the top, to get the dished surface as close as possible to the edge of the engineering square, I had to tilt the top of the blade to the right. The teeth, however, only travel around the circumference of the blade. By aligning the dished surface to the table top, I had misaligned the teeth such that the teeth at the top of the blade were closer to the right while those near the table stop were closer the workpiece.

This is a little confusing as the blade washer should have and opposing profile to the arbor flange. This disallows blade plate distortion. Is this not the original washer or arbor perhaps? Good luck with your pursuit and please let us know what you find ;-)

[phil harold]

This is a little confusing as the blade washer should have and opposing profile to the arbor flange. This disallows blade plate distortion. Is this not the original washer or arbor perhaps? Good luck with your pursuit and please let us know what you find ;-)

Since you checked all the other things during a tune up, we can now take those out of the equation

Glen is right on washers
On my jet I have 4" Blade Stabilizer on each side of the blade,
then the stock blade washers

Like these:

http://www.toolstoday.com/p-5322-saw...37_a_7cSTF_d_4

and with all threads, we like to see pictures
so show us you saw, zero insert, and a pretty piece of wood

[Bill Huber]

I agree, if you can cove the blade by turning the arbor nut you have a problem with that but I am not saying that will fix the other problem but it should be corrected.

[Chris Parks]

Check the square? Also so to get a longer reference on the saw blade, crank it down very low, remove the ZCI and use the square upside down so it lays against the blade under the table. You then see the blade of the square over the whole of the saw blade.