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Thread: table saw tuning......

  1. #1
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    table saw tuning......

    Curious as to what number is considered very good in a table saw setup. My blade is just about dead on as far as the blade to the miter slot but miter slot to fence is about .003 off. I mean that the end of the fence on the back side of table saw is .003 away from blade than the front part of the fence. I have only set up this saw once and had another person helping me or well pretty much doing it but that has been many years ago. I dont mean to be ignorant but I dont have a problem asking questions when I am not sure.
    "To me, there's nothing freer than a bird, you know, just flying wherever he wants to go. And, I don't know, that's what this country is all about, being free. I think everyone wants to be a free bird." - Ronnie Van Zant

  2. #2
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    Karl, if you ripped a 4 foot length of plywood or MDF, with one side flat and straight, what is the difference in the widths at the ends? And what difference are you comfortable with?

    Regards from Perth

    Derek
    Last edited by Derek Cohen; 03-24-2019 at 8:18 AM.

  3. #3
    Its customary to have the back side (post cut)be a few thousand wider to allow the wood to expand from the cutting process.

  4. #4
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    well I did what Derek had explained and for a 4 foot piece of plywood it was perfect as a tape measure goes. I am pleased. 6.5 inches on each end. Not dealing with very small tolerances on a daily basis tends to make me not be able to put .003 in perspective. I did use an A-Line-it deluxe kit to help with this.
    "To me, there's nothing freer than a bird, you know, just flying wherever he wants to go. And, I don't know, that's what this country is all about, being free. I think everyone wants to be a free bird." - Ronnie Van Zant

  5. #5
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    Quote Originally Posted by George Makra View Post
    Its customary to have the back side (post cut)be a few thousand wider to allow the wood to expand from the cutting process.
    George, I imagine that the ideal/best design for a rip fence could see it running parallel to the mitre slot (and blade), but only extending to the middle of the blade, itself?

    I have not compared the quality of a rip cut with short- and long fences. Has anyone here?

    Regards from Perth

    Derek

  6. #6
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    That .003" is thinner than a sheet of ordinary copier paper. Sounds dead nuts on to me.

    IMHO, some people make far too much of stuff like this. We're woodworking, not machining, and this ain't NASA.

    I generally allow about 1/32" of clearance (that's over 10X your .003") at the back of the blade, as George said, to give clearance if the kerf releases stresses and/or the wood moves after the cut, to help prevent burning/kickback. YMMV.

  7. #7
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    Rip a piece but stop as soon as you clear the front teeth and shut off the saw. Look at the cut on both sides of the board or mdf. If you can see the back teeth on the fence side and a slight ridge on the front end, you know the back teeth are cutting and the fence is set too far out of square towards the blade. If the ridge occurs on the offcut, the fence is set too far out. If you can't see or feel any difference between where the front teeth cut compared to the back teeth on either cut you are good. I also measure the kerf vs the width of the teeth. to determine runout. The kerf should only be a few thou wider with a 10" blade, assuming the blade is good. Dave

  8. #8
    Forest blades use to have a real nice write up on setting up your saw. You can call them and ask if they could email it to you.

    It covers everything and IRRC it about 4 pages long.

  9. #9
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    At .003, I'd leave it alone. I think you'll find that just switching blades can change that number at least a thou or two, maybe more.

  10. #10
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    Quote Originally Posted by Nick Decker View Post
    At .003, I'd leave it alone. I think you'll find that just switching blades can change that number at least a thou or two, maybe more.
    Plus, saw blades are tensioned, which means you can't even measure them to the .003" level of precision or not in any way that matters unless they're running.

    Which ain't recommended.

  11. #11
    If you're using a tape measure then you're not really in the spirit of the post.

  12. #12
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    " Dead On" "Dead Nuts" " Very Good" "Tape measure" " It's Only Woodwork"
    To some 0.003" is a lot, to others it's nothing,
    it depends who you are, what you do, and what you care about.
    What is considered good is in the eye of the beholder.
    You are asking questions that you have to answer yourself.

  13. #13
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    I'm curious - you say .003" difference from the blade. So, is the .003" over the length of the exposed blade, or over the length of the fence?

  14. #14
    0.003 over the 27 inches of a Unisaw top is plenty square. Actually some folks would say too square; there is a school of thought that a fence should angle very slightly away from the blade to prevent the back of the teeth from catching the wood, maybe a 1/64 or so away from the blade over the length of the fence.

    Here is the thing about the 0.003; I am going to say that you can't even measure squareness that closely on a saw. First, to measure that accurately, you need better training, better tools, and most importantly, a better reference on the saw. Many machining operations are not done to within 0.001 over 12 inches; the main reason is that they do not need to be.

    There is a chance your miter slots are not within 0.003 of parallel to each other. The miter slot itself may not be 0.003 within straight of itself. It is highly unlikely your fence is within 0.003 of flat to itself. The front bar of the fence is probably not within 0.003 of itself over its length. I'm not sure of the runout spec for a Unisaw arbor, but I wouldn't be surprised if it was a couple thousands.

    Despite those tolerances, table saws work just fine for woodworking. Actually, I have used plenty of metalworking machines more out of tolerance than 0.003 over 27 inches, and they worked just fine for most metalworking as well. In one shop I worked at in college, we had a lot of WWII lathes and mills owned by the Navy on long term loan to the University. After 50 years of use, not everything was as good as when new. Whenever we complained about one, the bossman would say. "If it was good enough for MacArthur, its good enough for you!"

  15. #15
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    Quote Originally Posted by Mark Hennebury View Post
    " Dead On" "Dead Nuts" " Very Good" "Tape measure" " It's Only Woodwork"
    To some 0.003" is a lot, to others it's nothing,
    it depends who you are, what you do, and what you care about.
    What is considered good is in the eye of the beholder.
    You are asking questions that you have to answer yourself.
    It also takes some pretty sophisticated setups to even measure .003" accurately. For example, if the rod in your dial indicator isn't perfectlly perpendicular to your fence/blade/whatever, you're gonna get another .006" or so of error.

    Then there's the issue of the straightness of the materials used to construct your fence. On my Powermatic's Accufence for example, the factory BB panels that cover the rectangular tubing of the fence vary by probably five times that – .015" – in and out, like a sine wave, all along the length of the fence, due to the clamping pressure of the t-nuts used to fasten the BB to the tubing. But even if you stripped off the BB panels, unless you scrape and polish the steel tubing of the fence, a speck of rust is gonna quickly throw in another .010" or so.

    If you add to that the fact that your wood is going to move maybe five or ten times that .003" every time you so much as breathe on it, you quickly realize that three mils has as much meaning in this discussion as three Angstroms.

    I'd be interested to see the woodwork done by those who think half the thickness of a human hair is "a lot." This kind of thing gets silly after a while.

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