Is my thinking on this correct ?????

[Bill Huber]

I am on the kick of getting my table saw blade at 90°. I know we are working with wood and all of that but I would still like to have a way to make sure the blade is at 90° and not 89.9° or 90.1°.

So if I take a chuck of wood say 3/4" by 2 1/2" high and make a cut with the miter gauge on the left of the blade (2 1/2" up). Then move the miter gauge and rotate the wood 180° keeping the bottom on the saw top and make another cut. Now the off cut should be the same at the top and the bottom, correct?

If there is a difference in the top and the bottom of the cut off that would show that the blade is not 90°.

282068

[Dennis Ford]

Makes sense to me, assuming flat table and sharp blade; that should work.

[Steve Rozmiarek]

Bill, why not just use a machinist square? Your technique would sure work I'd think.

[Bill Orbine]

Your technique does make sense and that's fine to use is you prefer this method. I almost always use a machinist square but sometimes I'm a little lazy to go get it wherever it may be in the shop. You can check your blade square to table without the measuring tools! Get a good flat scrap even thickness about 15" long or so and make one cross cut about the center of the board. Shut down saw. Without flipping either pieces over meet the two boards together at the cut on a flat table (table saw is one) and you should see no gaps top or bottom. Now flip just one of those board over and meet the two together at the same cut. If you got a gap at top or bottom, then your blade may not be set 90 degrees to table.

[Matt Neil]

I think that will give you a parallel cut, but not necessarily help you figure out if the miter gauge is set to 90. I tried drawing pictures on some scratch paper with a miter gauge set to 45, and I think the measurements are equal on that one too. Of course, I might not be understanding your technique, and my crude sketches have no accuracy. By try an extreme angle and see verify against those results too. Or maybe you just can't flip the piece of wood 180.

[Charles Coolidge]

If you are trying to achieve 90.0000 degree accuracy (I approve of this goal :D) you are in the zone where hand pressure, rate of feed, e.g. the human factors come into play even if your tools are dialed in at 90.0000, just saying.

[Marc Myers]

http://www.rockler.com/wixey-digital-angle-gauge

I have one of these. Not too expensive and works for any angle. Just set it on the table and zero it out, then attach it to the blade via the magnets and it tells you the angle of the blade in relation to the table. Works great.

[johnny means]

A better way to see any error is to cut a block in half. Flip one piece over them butt the cut ends back together. Any degree of error will be doubled more apparent.

[Charles Coolidge]

http://www.rockler.com/wixey-digital-angle-gauge

I have one of these. Not too expensive and works for any angle. Just set it on the table and zero it out, then attach it to the blade via the magnets and it tells you the angle of the blade in relation to the table. Works great.

I have one of these Marc, works great. It jives with the electronic angle meter built into my table saw and with my Starrett measuring tools.

[Keith Weber]

I don't trust the tilt gauge on my Grizzly cabinet saw, so I just use my Incra square so that the fat part is tight to the cast table and align the vertical part of the square so that it is flush to the side of the fully-raised blade and between a couple of teeth. Rotate the tilt handle until there's no light sneaking through and lock it down. Takes just seconds to do after you've tilted your blade for another purpose.

Keith

[Jim Finn]

http://www.rockler.com/wixey-digital-angle-gauge

I have one of these. Not too expensive and works for any angle. Just set it on the table and zero it out, then attach it to the blade via the magnets and it tells you the angle of the blade in relation to the table. Works great.
This is what I use.

[James Tibbetts]

I can't see any better way to get square to the cut.

[John Coloccia]

I think you'd do better with a square, Bill. Your method works, sort of, but in practice I think you'll have errors creeping in from:

1) miter gauge...is IT exactly 90 degrees to the blade? If not, the cut will taper and you'll have to be extra careful to measure in exactly the same place
2) and I think this is the killer....the offcut is free to flop around. It will whack into the blade as you make the cut, and certainly the very end of the cut could be truly awful.

With a square, your eyeballs, and a light, you can "candle" the gap under the square and see quite a bit better than .001"...noooooo problem. In fact, you'll find that you probably can't get it absolutely perfect because you'll start chasing gaps that are truly tiny before you realize just how small they are. :)

[Roy Turbett]

A better way to see any error is to cut a block in half. Flip one piece over them butt the cut ends back together. Any degree of error will be doubled more apparent.

+1 on what Johnny says. If you pass a perfectly parallel 3" high block through your blade with the miter gauge at 90 degrees and flip one end over (part that was on the table is now on top) and rejoin the pieces, you will get twice the error. In other words you will see how far your blade is off over 6 inches. You will also see what direction is off by whether the any gap is on the top or bottom. I first saw this described in Jon Eakes book, Fine Tuning a Radial Arm Saw.

[William C Rogers]

+1 on what Johnny says. If you pass a perfectly parallel 3" high block through your blade with the miter gauge at 90 degrees and flip one end over (part that was on the table is now on top) and rejoin the pieces, you will get twice the error. In other words you will see how far your blade is off over 6 inches. You will also see what direction is off by whether the any gap is on the top or bottom. I first saw this described in Jon Eakes book, Fine Tuning a Radial Arm Saw.
I use this same method, the wood must be parallel. I use a 6-8 block. This method is in my JoinTech Smartmiter manual.

[Brian W Smith]

I thought it was spelled hysteria........it's hysteresis,duh.I was right in it's definition though.

http://www.toolingu.com/definition-350115-5917-hysteresis.html

JMO,but you have hysteresis within your cutting action.Trying to measure its path is going to prove difficult.I'd back the truck up,so to speak,refine how each part of the problem(in this case,the saw,the mitre track,the mitre gage,ect)or action is taking place.An example would be to add a significant amt of weight to your mitre gage.....then clamp the part to it.

The problem and again,JMO......is the above dosen't directly change any mechanical errors(mitre track clearance for ex).But,it changes the feel that the operator has.It allows you some momentum within the action...which goes pretty far to resist certain errors from happening.Ex:you're having to hold an unweighted,unclamped pce pretty firmly to make your cut.Add 10 lbs and a clamp and you could potentially push it with one finger and have a better cut.It explains why sliders work so well.Good luck.

[Roger Pozzi]

A better way to see any error is to cut a block in half. Flip one piece over them butt the cut ends back together. Any degree of error will be doubled more apparent.

Plus 1 !!
Very accurate and fast.

[Bill Huber]

Thanks for all the input....

I have used the block and flip it over, I guess there should be a little explanation on this.

The way it started was a friend needed to make a panel and really didn't want to because they never came out flat. I went over all the ways to make the cuts so you would get a flat panel and found that his combo square was a cheap one he had gotten at HD.

So I wanted to come up with a way he could measure it, not just use his eyes but measure it. This did work and we found that his combo square was not square, he has now ordered a good one.

He will also be cutting on both sides of the blade to make sure the board will come together and make a flat panel.

[Ole Anderson]

Pick up a small drafting triangle at an arts and crafts store or online. They are just about dead-on as you can get. I have a small 45/45/90 and a bit larger 30/60/90, both bright orange.

[Rich Engelhardt]

Ole beat me to it about the triangle.

I usually go to Lowes and pick up a half dozen or so Swanson Speed Squares (the orange plastic ones) and take them home & check each one against my Starrett combo square.
I keep the one that's dead on and return the rest.