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Thread: Sled and zero clearance questions

  1. #1
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    Sled and zero clearance questions

    I have 2 different questions.

    1. I got my sled finished and was testing it for square, I use the 5 cut method with a 6 inch board.
    I measured it with my calipers in the inch mode and came up with .2835 on one end of the last cut and .2890 on the other. I then switched to fractions on the caliper and came up with 9/32 (.28125) on each end.
    So should I say that is good or do I need to work at getting it closer and just use the inches on the calipers?

    Some times these number just get all screwed up in my brain, that is I think I have one. My Dad always told me that when the Good Lord was passing out brains, I thought he said trains and said I had one.... and I do have a train.

    2. I made a zero clearance insert for the TS and put it in but it sure make a lot of noise when it is running. It is made out of Phenolic and I raised the blade thought it 3 or 4 times with no change. Do I need to file the opening just a little wider or is there something else that I have done wrong.


    Thanks....
    Last edited by Bill Huber; 07-21-2007 at 10:56 PM.

  2. #2
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    Myself, I'd try to improve it .. .. but if you're happy with the joints it produces, that's fine. From your numbers. it sounds like it's "out" by approx. 4 thousandths per running foot .. .. not bad, but not great either. Making it better depends on how difficult it will be to adjust your fence .. .. if you've provided for easy adjustment, I'd go for it .. .. if not .. be happy with what you've accomplished.

  3. #3
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    Dont have an answer for #1 but the ZC insert noise is somewhat normal on a new one and should go away in time. One thing you can do though is put a dado set shim or piece of paper on the arbor then re-raise the blade. That will open it up a few thou on one side.
    Use the fence Luke

  4. #4
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    Quote Originally Posted by Bob Wingard View Post
    Myself, I'd try to improve it .. .. but if you're happy with the joints it produces, that's fine. From your numbers. it sounds like it's "out" by approx. 4 thousandths per running foot .. .. not bad, but not great either. Making it better depends on how difficult it will be to adjust your fence .. .. if you've provided for easy adjustment, I'd go for it .. .. if not .. be happy with what you've accomplished.

    That is what I needed to know, I guess I really need to keep working at it. I want it write.....

    Thanks.

  5. #5
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    Quote Originally Posted by Doug Shepard View Post
    Dont have an answer for #1 but the ZC insert noise is somewhat normal on a new one and should go away in time. One thing you can do though is put a dado set shim or piece of paper on the arbor then re-raise the blade. That will open it up a few thou on one side.

    I knew someone would have the answer, I will stick a shim in it and brign it up again.

    Thanks.....

  6. #6
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    five cut method?

    Forgive my ignorance but what is the 5 cut method?

  7. #7
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    Quote Originally Posted by Stephen Pereira View Post
    Forgive my ignorance but what is the 5 cut method?
    Well you take a square board and cut one side, then rotate the board clockwise and put side one against the fence. Make cut 2 and rotate the board clockwise and put that side against. Then make cut 3 and turn the board and then cut 4 and turn the board. At this point you are back to side 1 being next to the blade, cut a 1/4 inch or so off and measure each end.


    http://www.thewoodshop.20m.com/calibrate_sled1.htm

    http://www.thewoodshop.20m.com/five_cut_method_swf.htm

  8. #8
    Quote Originally Posted by Bob Wingard View Post
    Myself, I'd try to improve it .. .. but if you're happy with the joints it produces, that's fine. From your numbers. it sounds like it's "out" by approx. 4 thousandths per running foot .. .. not bad, but not great either. Making it better depends on how difficult it will be to adjust your fence .. .. if you've provided for easy adjustment, I'd go for it .. .. if not .. be happy with what you've accomplished.
    Isn't he off by .00275 (two-thousandths) per foot?

    (.2890-.2835)/(6*4)

    That isn't bad. About as thick as a thin piece of paper over a foot. AND, you have to take into consideration that you have five chances to screw the process up. That is why I prefer just using a larger workpiece and a good, trusted square to set my sled up.

  9. #9
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    I would adjust and try again. It is not hard to get much closer to square than you have gotten. You will appreciate the difference when making mortise and tenon joints.

  10. #10
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    Bill, I would leave your crosscutting sled just the way it is right now. You've managed to get it pretty accurate which is no easy feat with a sled as I've learned from personal experience. My exaktor sliding table is off by 0.005 but you know what? I haven't lost any sleep over it yet! Your zero clearance insert may be rattling if it doesn't fit snuggly in the throat plate. The solution would be to shim underneath or on the sides to get it fitting tight.

  11. #11
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    I agree..don't beat yourself in the head too much. There are too many variables to deal with. Your sled might be as good as you can get because your miter slots could account for some of it.

    Gary K.

  12. #12
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    Quote Originally Posted by Phil Thien View Post
    Isn't he off by .00275 (two-thousandths) per foot?

    (.2890-.2835)/(6*4)

    That isn't bad. About as thick as a thin piece of paper over a foot. AND, you have to take into consideration that you have five chances to screw the process up. That is why I prefer just using a larger workpiece and a good, trusted square to set my sled up.
    Actually, if he is making 5 cuts and then measuring...wouldn't you have to divide by 5...then the sled would be off by only .0008. It is a accumulative thing.
    Gary K.

  13. #13
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    The 5 cut method is good because it does amplify the error. In this case, I think it is going to be very difficult to improve on the current adjustment. You could make it worse. What you should do is repeat the experiment a couple of times. I bet you will find that the repeatability error of your results will be larger than the original error you measured. You are not dealing with machine tools.

  14. #14
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    Quote Originally Posted by Bill Huber View Post
    2. I made a zero clearance insert for the TS and put it in but it sure make a lot of noise when it is running. It is made out of Phenolic and I raised the blade thought it 3 or 4 times with no change. Do I need to file the opening just a little wider or is there something else that I have done wrong.


    Thanks....
    What is holding your ZCI in place? Single screw, spring tab, gravity? If gravity I would confirm that it is evenly supported and then perhaps use some tape (or something fancier if you like) to shim the side for a tighter fit.

    P.s. Remember to divide your 5-cut error by 4; that's your error per pass.
    Last edited by glenn bradley; 07-23-2007 at 1:21 AM.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  15. #15
    Quote Originally Posted by Gary Keedwell View Post
    Actually, if he is making 5 cuts and then measuring...wouldn't you have to divide by 5...then the sled would be off by only .0008. It is a accumulative thing.
    Gary K.
    I think my math is correct, he is off approx. .003" over 12".

    I do stand by my previous statement that I'd rather my Starrett square tell me my workpiece is square rather than using a caliper on a cut-off.

    FWIW, I can EASILY see .003" over 12" with my Starrett. I can see .001" over 12". I really see no need for the five cut method when my Starrett allows me to quickly and directly check my workpiece, and I never need better than .001".

    I guess the five-cut method would eliminate the chance that my Starrett is inaccurate. But I check it w/ other squares from time to time.

    If you think .001" is hard to see w/ a square, try this: Make a square cut (I know, chicken and the egg) on the end of a board. Hold your square so the blade is on the end grain. Hold up to the light, check for light passing gaps (should be none).

    Now, put a .001" feeler gauge between the wood and the blade and hold it up to the light again. That .001" gap passes quite a bit of light, doesn't it?

    I don't need any more accurate than that.

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