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Compound angles - how to calculate???

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  • Compound angles - how to calculate???

    I built the attached garden tool tray for my wife for her birthday, based on a pic I saw in Woodsmith Magazine. I angled the ends 15 degrees, and the sides 15 degrees. I used mortise and tenon joints to attach the sides and middle divider to the ends. All was going well until I tried to dry fit everything together. The sides fit tight into their mortises, but the other ends were angled in slightly, and wouldn't meet the mortise on the opposite end piece. Hmmm.

    After thinking about it, that made a certain amount of sense. If the sides were vertical, eg., 90 degrees, they would have fit fine at the opposite end. If the sides were turned 90 degrees to the end, they would be angled in at 15 degrees. So, since the sides were angled at 15 degrees, there must be some portion of 90 degrees that needs to be applied when cutting the ends of each side. I figured it like this:

    15 / 90 = 1.6666666 15 degrees as a portion of 90 degrees
    15 * 1.666666 = 2.5 # of degrees to apply to a compound cut of each end of the sides.

    According to this, I'd need to set my miter saw to 15 degrees horizontal and 2.5 degrees vertical while cutting the side pieces. Is this correct? Is there some sort of table that has this sort of info? I last had a math/geometry class in the 70's, so I need help...!

    Hope the above description of the problem makes sense. It took a lot of head scratching, and looking at the way things were fitting together, before it made any sense to me.Click image for larger version

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    Note that these are crappy cell phone pics and the color isn't even close.

  • #2
    Re: Compound angles - how to calculate???

    I don't know if this will answer your question but maybe it will............MiterMaster
    Teach your kids about 30 percent of their ice cream.


    • #3
      Re: Compound angles - how to calculate???

      That's great for mitered corners, which would be equally confusing. In the case of what I just built though, the sides were butted into the ends with mortise and tenon joints, so I think a different set of angles would be needed.

      Thanks for the link.


      • #4
        Re: Compound angles - how to calculate???

        Try this link


        • #5
          Re: Compound angles - how to calculate???

          Originally posted by Rambo View Post
          Try this link
          that looks like a great resource. thanks.
          there's a solution to every just have to be willing to find it.


          • #6
            Re: Compound angles - how to calculate???

            It's a trig problem. Nothing that can't be easily solved.

            44 and 10.5 degrees ought to do the trick.

            Here is a good refresher in the basic stuff