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Thread: compound angles calculating?

  1. #1
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    compound angles calculating?

    Hoping somebody help me understand how to calculate a compound angle cut.

    I have a table base. The legs are square tube splayed at 15 degrees out and back. I need to attach a square tube between them to tie them together.

    Perhaps somebody could direct me to your favorite tutorial,template making, or some old school knowledge.

    Current, I am not ready to punt and cut a hole in the tubing. I have not tried it in 3D CAD, yet.

    Would like to gain some understanding, as i think it would be a nice tool to have with out a bunch of trial and error.

    Thanks

  2. #2
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    Re: compound angles calculating?

    I use chalk or soapstone... marking the tubing inside the legs and outside the legs. Then connect the dots... but you have to have a stable hold that repeats for this. It also alleviates errors if you are careful and place each "gusset" in before welding.

    I am sure there is a more high tech technique but this is what I do and it hasn't failed yet.

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  3. #3
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    Re: compound angles calculating?

    Thanks. Funny, I hadn't considered using a grinder to hand cut the angles. I can see it minimizing error and address the potential offedness of my leg angle. That is probably the approach I will need to take at this point. Since, i want the tube centered, I could transfer the marks/angles where ever they need to be.

    Still, Trying to understand the compound angle thing. So, I can set up and cut on a band saw.

  4. #4
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    Re: compound angles calculating?

    Can you show pics of what you are working on?


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  5. #5
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    Re: compound angles calculating?

    I just make sure my legs are longer than they need to be. That way when I screw it up, I can try again.

    I usually just do them with a grinder much like Mac said.

  6. #6
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    Re: compound angles calculating?

    Just set the bevel on your saw for a 90* cut, then add 15*. Then put the tubing in the saw on the diamond instead of flat.

  7. #7
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    Re: compound angles calculating?

    Thanks. Mac, that worked in shorter order.

    Bob, again funny, I sketched it in 2D. calculated the length of the 15 degrees legs in 2D. Then came up short since other 15 degrees was not taken into account. I did not expect it to reduce the height an inch.

    Jeffrey. I may post a photo when welded. It is just a dining table base.

    Walker, the part needs to sit with flat side parallel to the ground??? I cut the legs at 15 degree bevel and 15 degree mitre. I am not sure that actually gives 15 degrees splay as I stated, from what I read.

    Thanks to all

    I still would appreciate input if somebody has a theoretical approach the compound angles.

  8. #8
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    Re: compound angles calculating?

    Try this, it is for machinist with a compound sine plate,

    http://www.auto-met.com/subtool/stcat/st_137.html

  9. #9
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    Re: compound angles calculating?

    Thanks, Jones.

  10. #10
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    Re: compound angles calculating?

    I've only set up a compound angle cut on my saw a couple times and it's a pain in the rear. But if I understand what you're asking, you would set your saw to 15 degrees, then you need to raise one end of the piece you're cutting to 15 degrees.
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  11. #11
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    Re: compound angles calculating?

    Quote Originally Posted by ccs View Post
    I've only set up a compound angle cut on my saw a couple times and it's a pain in the rear. But if I understand what you're asking, you would set your saw to 15 degrees, then you need to raise one end of the piece you're cutting to 15 degrees.
    Thanks

    I was trying to connect the legs with cross member. I tried the 15x15 degree cut. It was not the correct angle. It wasn't a bad experience to cut it by hand. I think a belt sander would be in order if i had multiples.

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