Tuning Up Your Miter Gauge

When I first opened my woodworking school, I did not have a miter saw in it. We did all of our crosscutting on the table saw using a good quality miter gauge. Now, the key to making that system work is that you have to have the miter gauge set up correctly. Once you do, you have basically turned your table saw into a sliding miter saw with big capacity, as long as the miter gauge is doing what it's supposed to do. So, here's what I mean by that. We wanna make sure that the miter gauge is cutting perfect angles every time. Now, it's real tempting when you're setting up tools like this to take a good quality square, put it against the miter gauge, put the head of the square against the blade. Couple things I don't like about that. The big thing is that, what I really wanna know is how this performs when I'm cutting not how it performs when everything is sitting still. So, whatever dynamics are involved when the table saw is running, I want 'em to be involved when I'm setting up the miter gauge. So, one way that people will do test cuts is to put a board in the miter gauge, cut an end square, and then test it. What I wanna do is take advantage of what I would call cumulative errors. So the way I'm gonna set up the miter gauge is, I'm gonna angle it to 30 degrees, create a six-sided object. And that has the effect of magnifying the error that I have so that I can really fine-tune the miter gauge and get it just right. So, first step, let's get the miter gauge pivoted out to 30 degrees. I'm gonna lock that in. Now, what I need to do is plug my saw in, and I'll get one end of all six pieces cut to that 30 degree angle. With one end of every board cut, what's key now is that we get every board exactly the same length. So, this is the benefit of a stop on a miter gauge, like this one. I'm gonna slide this over so that when my material goes against it, it's gonna lock it in place and I can get all these parts to exactly the same length. Now, when you do this, one of the things to be aware of is that we have a sharp knife edge here on this cut. So we wanna make sure that that knife edge can't creep under the stop. So you wanna make sure that like this one, once that stop is in a closed position, it's gonna stay there and not slide up that angle. Now, I'm going to come back and I'm gonna cut all the other ends off, and then I'll show ya how we actually check the setup on the miter gauge. What that gives us is six pieces, all cut at exactly the same angle, all cut to exactly the same length. We can use these to use that cumulative error idea and find out just how accurate our 30 degree cut was. I've got all the boards cut and I wrapped them in a band clamp here so that I can put that whole circle together and see what I've got. Now, here's what's happening. I've got a bunch of seams on here that are absolutely perfect, five of the six. And the way that it happened is, I kind of manipulated the board as it went into the clamps. On seam number six over here, it's touching at the bottom of the seam, but it's open out here at this end of the seam. Now, this is what's cool. This is the cumulative error business. This gap right here is the net effect of six seams being off just a tiny bit. So, this is just a tiny, tiny error. The error is actually 1/6th of the amount of daylight you can see right there. So if we had only caught one board and put a square on that one board, that'd be such a tiny amount, you might never see it, but this magnifies it. So, at this point, what you do is, follow the manufacturer's instructions, tweak your miter gauge. You cut all the boards again, both ends of every board. Use your stop again to make sure they're all the right length, put 'em back in the band clamp and get everything set up until that error goes away. So this one's gonna need just a small adjustment. Now, what's cool is that with a good miter gauge, once we've got that set at 30 degrees, I can toggle this back to 90, 22 1/2, 45, whatever angle I need, and have that same accuracy that I had at 30 at all those other angles. So it's definitely worth taking the time and once you have this set up, it really should be a once in your lifetime thing. So, take your time, do it right, and make sure that your miter gauge is accurately cutting and providing all the accuracy it can for you on your table saw.