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  • the angle on angles

    I was trying to make a "/\" frame and was trying to figure out what the angle had to be to have the 2 pieces join at the top.
    I actually used trig to calculate what I "thought" would be the correct angle(didn't know i would actually *use* that stuff i learned in school!)
    I have encountered 2 problems so perhaps someone can help me figure this out.

    Here are the specifics. I am trying to join 2 pieces of 1/2" thick plywood(about 4"wide) to create some shade for a few plants that don't like direct sun.
    They will span a planter that is 19.5" wide.
    I want the tip of the V to be 23" tall.
    First, please check my math.
    I want the 2 pieces to meet in the middle, so the length of the base is 9.75" (19.5/2)
    the height will be 23"
    tan@=opp/adj 23/9.75=2.359 arctan 2.359=67 degrees
    so, the angle between the planter and the /__ member is 67 degrees(internal angle)
    there is my first problem....how do I cut a 67 degree angle? (complement of 67 is 23....do i need to cut a 23 degree angle?)

    I figured the angle at the top of the /\ to be 23 degrees
    tan#=opp/adj 9.75/23=.424 arctan.424= 23
    23 degrees between the 2 members
    does this mean i need to cut 23/2(11.5 degrees) at each end?
    when i did this, the two members did not meet at the top.

    what am i doing wrong?
    also, how do i cut angles >45 degrees on the 2424 table saw?
    thanks for your help

  • #2
    I think that when you calculated the angle at the top, you divided the "/\" frame into 2 right triangles. Thus the arctan of (9.75/23) already gave you half of the full "/\" angle which is the you angle that you need. You don't need to divide that again.

    The full angle would be 46. The other base angles "/_" and "_\" of 67 are correct. The sum 67 + 67 + 46 = 180 as it should.

    You should be able to cut angles between 45 and 90 degrees by using the left side of the saw blade (between 90 and 135 on the right side).
    Mark

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    • #3
      I believe that would explain it!! (duh i feel dumb)
      as far as using the right side of the blade...is that safe? I think there was some kind of warning about doing that

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      • #4
        I think the problem is that with the fence on the left side you can "pinch" the board under the blade and between between fence "|_\"which presents a good opportunity for kickback. You can do it, it is just better not to. When the fence is on the right side of a left-tilt saw, it cannot become "pinched" under the blade. A better solution is probably to keep the fence on the right side of the blade. Instead of using the fence-blade side to cut the board to length, use it to remove the scrap portion of the board (if that makes sense).
        Mark

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