Table Saw Tuning

Article - February 4, 2008

This week’s question comes from Peter from Charlotte, NC. He writes:

“I have purchased a used General International cabinet saw from a professional shop that was going out of business and I have a question regarding its set up. Using an alignment tool that I borrowed from the Charlotte Woodworkers Association I have been able to measure the alignment of the saw’s 10″ blade to the miter slot. According to the dial indicator, the back of the blade is 0.011″ further away from the miter slot than the front of the blade. In your opinion, is this amount significant enough to warrent loosing the bolts holding the cast iron table top and trying to get it to line up perfectly (say +/- 0.003″)? Or should I leave it like it is and just try to line the fence up to the blade as best I can? That actually brings up a follow-up question: should I try to have the fence align with the blade perfectly or should I have the fence slope away from the plane of the blade at the back so that wood doesn’t get pinched between the blade and the fence and kick back? How much of a gap does one put on the back of the fence if you do this?”

And here was my reply:

“Hi Peter. First off, congrats on the new saw! Now down to business. Let me start by saying that I tend to fall on the “less picky” side when it comes to machine setup. Personally I don’t believe that a pair of calipers or a dial indicator is necessary to set up any woodworking tool (ok there may be a few). But I don’t consider the tablesaw to be one of them. That being said, I would never discourage someone from trying to get things as close to perfect as possible. Its your machine and your time, and obviously better is better, right? But in my shop, a pair of magnifying glasses and a 1/64″ graded ruler work just fine.”

“So the heart of the question is, “How much error is too much?” And please keep in mind that this is only my opinion based on my experience. You will find MANY different opinions on this topic. And many will vehemently disagree with what I have to say. But after all your research, you have to do what your gut tells you. Now I find it easer to judge these numbers when I see them in the form that I use everyday: fractions. So 0.011″ is just about 1/90th”. The smallest measurement I ever use in the shop is 1/64th”. So 1/90th in my mind is about the same size as dandruff off a dust mite. Ok, maybe it’s not that small. But if my saw had an error of 1/90th”, would I ever even notice it?? Probably not.”

“But there are two other components to this issue that we need to consider: safety and cut quality. From what I can see, a blade that is slightly further from the fence at the back really accomplishes the same thing as a fence that slopes away from the blade. So having the blade off ever so slightly doesn’t strike me as a hazard in any way. And I am theorizing that it might actually be safer when ripping. (Emphasis on theorizing).”

“Now cut quality is the one area that might concern me. The blade tilting in that direction means that your rip cuts will be squeeky clean. Anything cut from the right side of the blade will be perfect because there is no significant contact with the teeth at the rear end of the blade. And a little known fact is that certain tool companies actually use this technique on their circular saws in order to get the best cut quality possible. But what about the left side of the blade? Think of a cross-cutting operation with a miter gauge. The work piece will be cut ever so slightly by the back teeth, which means increased tearout since the back teeth cut upwards. And remember, when you line up your cut at the front of the blade, the actual cut will be 1/90th” off after you pass over the back teeth. Again, is that enough to be concerned about? Probably not in my shop.”

“So now you are even more undecided than you were before. lol. Let me just tell you what I would do at this point. You already have the dial indicator. Get the saw in position, loosen the bolts for the top, and try to get the blade as parallel as possible to the miter slot. This isn’t something you are going to do all the time, so you want to take your time and be a little picky. This way you are starting out on the right foot from day 1. And in all likelihood, this saw will hold its setting for a very long time. Furthermore, you will get to know your new saw. And whenever you check alignment in the future, you can make the decision on how picky you want to be based on everything you’ve learned.”

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