Table Saw bevel angle problems

This week i've been building a small end table that is essentially just a mitered plywood box. On the first go around, i set up the blade to 45 using the wixey gauge and then cut all the bevels. I go to put the thing together and my angles are off. The sides angled in about 1/8" over 6 inches. Each bevel was off by about a half a degree.

So then i got to trying to figure out what was wrong.

I checked the wixey gauge first. I put my starrett combo square in the vise, set the gauge on the face, zeroed it, then put it on ruler. it read a perfect 90. I checked the starrett for square using the draw a line and flip it over draw another technique, and it was square too.

Then i went to the saw. The blade is perfectly square to the miter slots and the fence. I set it up only a few months ago, and i rechecked it tonight, at 45 and 90, rotating it and measuring off the same tooth, and it was all still good.

I got a piece of wood, put the blade to 45 using the wixey, checked it against the 45 on the starrett, it was flush. I made a cut, put the two halves together, and..it was acute. off by about a degree.
I put the wixey on the table, zeroed, and then on the bevel cut, it read 44.6. I put it on the blade, it read 45. I move the blade to 45.4, make a cut, put the bevels together and its a perfect 90. So at least now i know my cuts are off by .4.

What the heck causes this!? Could the blade be off? I just put a new blade on this week, an Irwin Marples one. I don't know what else to check at this point.

Thanks in advance for the help.

I have a wixey gauge that does not read consistently. However, your situation seems to be different. How flat is your blade? You might also try using a different blade. If it produces the same error, at the least you’ll be able to eliminate the blade as a source of the problem.

An angle gauge is useless if your blade is not aligned at 90 degrees and at beveled angles. Most often bevel alignment is checked at 45 degrees but, any severe angle will do. Most contractor format saws do not stay aligned when the carriage is tilted and I would not spend much time chasing that unicorn. A heavy set of cabinet mounted trunnions can certainly be aligned for true cuts at 90 and at 45 and everything in between.

Use the same method you use for confirming alignment at 90 degrees and check with the blade tilted to 45 degrees. If that passes muster we can move on. I use a shop made rig like so:

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I set my blade tilt angles with my Beall tilt box, which has about the same accuracy and repeatability of the Wixey. Those gauges only get you really close, but a quarter of a degree time 8 cuts is 2 degrees. When I do work like that where all the angles have to add up to be perfect, I cut my pieces extra long so when I do the test fit and it is off a tiny bit, I can tweak the angle and shave a hair off all the pieces and test fit again. Once the test fit is perfect, I trim all the pieces to the finished length. I would recommend this approach for future projects.

Is your table saw level?
You won't get a good read unless your table is absolutely level.

Like Glenn said, jobsite/contractor saws are notorious for not beveling well. What saw are you using?

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Originally Posted by liam c murphy

I have a wixey gauge that does not read consistently. However, your situation seems to be different. How flat is your blade? You might also try using a different blade. If it produces the same error, at the least you’ll be able to eliminate the blade as a source of the problem.

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I put the blade flat on the table and tapped around the edges, it made noise, so its not perfectly flat. When it's running you can see the slightest bit of wobble in the teeth, so it may likely be the blade that's the issue. It cuts consistently, now i just have to adjust for the error until i can afford a nicer blade.

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Originally Posted by glenn bradley

An angle gauge is useless if your blade is not aligned at 90 degrees and at beveled angles. Most often bevel alignment is checked at 45 degrees but, any severe angle will do. Most contractor format saws do not stay aligned when the carriage is tilted and I would not spend much time chasing that unicorn. A heavy set of cabinet mounted trunnions can certainly be aligned for true cuts at 90 and at 45 and everything in between.

Use the same method you use for confirming alignment at 90 degrees and check with the blade tilted to 45 degrees. If that passes muster we can move on.

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I don't have a gauge like that, but i did measure at 45 off the miter slot and the tooth touched the same 64th each time and on multiple teeth. It's possible that it could be off by less than a 64th, but that wouldn't be enough to give me .4 degrees off on one cut.

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Originally Posted by Nick Decker

Like Glenn said, jobsite/contractor saws are notorious for not beveling well. What saw are you using?

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I've got a 3 month old Grizzly G1023. The blade body angle reads 45 all the way around, but it cuts at 44.6. It's almost like either the blade changes angles once it starts up or the blade's teeth are off enough to cause the error. It is a thin kerf blade, and i am planning to buy some stiffeners to try to help it.

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Originally Posted by Lee Schierer

I set my blade tilt angles with my Beall tilt box, which has about the same accuracy and repeatability of the Wixey. Those gauges only get you really close, but a quarter of a degree time 8 cuts is 2 degrees. When I do work like that where all the angles have to add up to be perfect, I cut my pieces extra long so when I do the test fit and it is off a tiny bit, I can tweak the angle and shave a hair off all the pieces and test fit again. Once the test fit is perfect, I trim all the pieces to the finished length. I would recommend this approach for future projects.

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This will be my approach going forward, and has kinda been my approach till now as well. I re did the cuts this morning after adjusting for the error, and everything came out square.

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Originally Posted by George Makra

Is your table saw level?
You won't get a good read unless your table is absolutely level.

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Tilt boxes measure a delta. You zero them to one surface and measure the difference to the other.

Is there a reason you're using a narrow kerf blade? If it were me, I'd skip the blade stiffeners for the narrow kerf blade and put that money toward a decent reg. kerf blade, preferably not an Irwin.

I agree with Nick,

You have a real cabinet saw, might as well put a real blade on it...

To me this his would be the first step in solving the issue.

Bill

Edit. I see you were able to compensate for whatever is happening and made successful cuts. But we still don’t know if the cause is deflection of the thin blade or something else. Trying a standard thickness blade may help to determine the root cause.

I wonder about your insert..is it perfectly level with your table..I had issues yrs. ago and I realized my wood was dropping a bit onto the insert.

Jared,

I had that problem. You did the right thing, well, obviously, because it worked.

If you expect to make many bevel cuts in the future that have to be perfect, I feel that you should consider these choices: (1) make a shooting board called a donkey's ear for shooting perfect 45's and/or (2) make a 45* sled. It is easier to make 45* miters than to make 45* bevels. The picture below is of a panel-raising sled (more like 30* as I recall, but you get the idea) If you like books, get a copy of The Accurate Table Saw by Ian Kirby. A used copy will set you back about $4-5. Money well spent.

This is a teachable moment. Wixey gauges, miter gauges, etc. take you only so far toward accuracy. After that, you don't "measure" you adjust. That's what you did and it resulted in an accurate 45. Making a jig is just a quicker route to creeping up on your target.

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