Compound miter problem

[jhmiii]

I am trying to construct a tetrahedron from six long pieces of wood. Using a web angle calculator (at that point I was not a member of the group and had not seen a great video posted here on compound angles without math) I found I needed the miter angle set to 30 degrees and the blade tilt to 54.7 degrees. My problem is that my blade will only tilt to 45 degrees (actually less since it is a very old table saw). I attempted to fake this by constructing a jig that tilted the workpiece to 54.7 degrees, but this gave the wrong angled cuts. Putting three pieces together left a big gap in the middle. Any and all advice, critique, commentary is appreciated.

[JR1]

The problem that you are having may be the same that I had trying to make a Three-Way Lock Miter Joint (see p18 of Domino Supplemental Manual by Rick Christopherson . I tried to cut the angles with a very accurate track saw but didn't succeed until I used a miter saw—don't really understand why—you may be having the same problem.

[mike4244]

Try this angle,35.3°. This is 90°-54.7°
mike

[jhmiii]

Mike, I tried 35º, but was still using a miter of 30º , so there was still a large gap (est. 10-15º). Do you think using the difference with 90 on both blade tilt and miter will work?

By the way since you used the º symbol, I explored a bit and found it is option-0 on my Mac keyboard.

Thanks for making me think and of course, the input.

[Boatman53]

For those using iPads the degree symbol is found by holding the zero and a blue window opens above it, slide your finger to the blue and you get one of these °. Other than that I can't help.
Jim

[mike4244]

jhmiii said:

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Mike, I tried 35º, but was still using a miter of 30º , so there was still a large gap (est. 10-15º). Do you think using the difference with 90 on both blade tilt and miter will work?

By the way since you used the º symbol, I explored a bit and found it is option-0 on my Mac keyboard.

Thanks for making me think and of course, the input.

---

I do think using the difference between 90° and 54.7° will work. and may work for the other part of the compound,try it.
By the way I type 0176 while holding the ALT button and pushing the + button. This gives you the ° sign.This is for Windows.

mike

[jhmiii]

Thank you all for your thoughts. The N-sided pyramid calculator is what I used to get the 30º miter and 54.7º blade tilt. I have since tried tilting the workpiece at 35.3º and mitering at both 30º and 60º. Neither is close, in fact the 60º miter with the 35º tilt was so far off I could barely recognize how the parts were supposed to fit.

I am now considering the video "Small Woodworking Shop Tips & Ideas" mentioned here some time ago. I figure I might be able to adapt his non-mathematical angle setting method to the tilted workpiece as opposed to tilting the blade. I will let you know if I can figure out how to adapt his method.

[JIMB49]

well i'm trying it goes back to trig. you had at way over 60 i'm been trying to figure this for the last 2.5 hrs so much for that e degree

[JIMB49]

i do know that the sum of any side must be 180

[jteneyck]

Try the N-sided pyramid calculator here and see if it makes more sense.

John