I have no idea how to get these angles correct

RickSanchez · Oct 29, 2020

Hi Knowers of All Knowledge,

I'm trying to create a pyramid roof for a small japanese bell (don't ask) and I'm having a problem with angles. I'm tilting my miter saw over to 20* because I want the pitch to be about 5/12. When I make my angled cuts however they always are off. I've attached photos. How do you figure this out???

Loren · Oct 29, 2020

These are fun trig problems, but there's a chart somewhere on the internet or drawing it in Sketchup will give you the exact angles.

This sort of tool may help you out too. http://www.pdxtex.com/canoe/compound.htm

wildwoodbybrianjohns · Oct 29, 2020

Use Pyramid angle calculator. Google that. You just put in base length of one side, plus height, plus number of sides, and it will do the magic trigonometry for you. In Inches or Metric.

I am currently working on box with a pyramid top, came out perfect.

If you want precision though, you should use a tablesaw and jigs. I can post some photos of what jigs I used, tomorrow, if you want.

For example, for my project:

RickSanchez · Oct 29, 2020

Thanks, WildWoods.

I think I'm getting lost in the terminology. I have no idea what the face angle is etc. I'm new to miter joints.

wildwoodbybrianjohns · Oct 29, 2020

the only one that is really important is:

Triangle segment edge bevel angle.

In your attempt you used 20º for the bevel.

Face angle is Slope, base to top.

RickSanchez · Oct 29, 2020

So in my case it says the base should be 6" and the angle you mentioned should be 14°. What should the bottom half of the miter saw be set at? 45?

351923 · Oct 29, 2020

Use this calculator (Rectangular Pyramid)
http://jansson.us/jcompound.html

Compare the angles given in the charts to my drawing and you will understand which angles to use where so that you can enter whatever sizes you want next time.

06132485 · Oct 29, 2020

I remember a time before computers, sometimes it wasn't pretty.

Killer link, thanks for posting it LeeRoy.

wildwoodbybrianjohns · Oct 30, 2020

Not 45º

It will be the angle of the triangle segment, relative to base. So, from the example I posted, the angle will be 50.2º.

So in my case it says the base should be 6" and the angle you mentioned should be 14°. What should the bottom half of the miter saw be set at? 45?

- RickSanchez

them700project · Oct 30, 2020

keeping things simple couldnt you cut it like crown molding?

Sylvain · Oct 31, 2020

If you don't like trigonometry, try descriptive geometry. ;-)
I will give you everything graphically. Then you transfer the angle with your sliding bevel.

I have no idea how to get these angles correct

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