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Need help with cuts for a pyramid!

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Forum topic by pashley posted 03-18-2017 09:49 PM 738 views 1 time favorited 17 replies Add to Favorites Watch
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pashley

1043 posts in 3533 days


03-18-2017 09:49 PM

Topic tags/keywords: pyramid

Hi,

I need help cutting a pyramid. I will be using ⅜” stock.

Here are the measurements of the pyramid when finished:

The rise is 2”, and it’s a square at 9 ⅜”

It will be mounted to a board.

My questions are: What are the blade angles for the miter joints, and the joint that will meet that board at the base?

Any other info is greatly welcome!

-- Have a blessed day! http://newmissionworkshop.com


17 replies so far

View jbay's profile

jbay

1800 posts in 715 days


#1 posted 03-19-2017 01:01 AM

47.4 miter
16.1 bevel

66.9 bevel at base

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jbay

1800 posts in 715 days


#2 posted 03-19-2017 02:24 AM

Correction:
47.4 is the angle of the triangle piece, the slide saw would actually be set for 42.6
Pretty sure the bevel is still 16.1…(or if the scale starts at 90 then it would be 73.9)

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

View firefighterontheside's profile

firefighterontheside

16740 posts in 1672 days


#3 posted 03-19-2017 02:41 AM

By my calculation, it’s a 23.1° angle of cut. You would have to stand your pieces up against the fence to make that angle. You will need 6 layers to get 2”. I’m thinking you glue 3 together that are 9 3/8 square. Then cut them. You probably need to use a sacrificial fence. After you cut that one, measure the short square on top and glue three more layers together that are that size. Now cut them at the same angle. That should make a pyramid that when set on the other one else, makes a pyramid that is 2” tall.

-- Bill M. "People change, walnut doesn't" by Gene.

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pontic

479 posts in 424 days


#4 posted 03-19-2017 02:51 AM

9 3/8” base but the height of the actual triangle is more than 2” isn’t it? How do you get the true height? so you can calculate the angle. It’s been 30some years since I did any complex geometry.
So how did you arrive at those angles? What steps?

-- Illigitimii non carburundum sum

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firefighterontheside

16740 posts in 1672 days


#5 posted 03-19-2017 02:56 AM

Rise over run. We know the rise is 2”. The run is half of the width at the base. I cheated and used a calculator to arrive at the angle, but otherwise it would have been tangents and cosines and the like. I too have forgotten how to use those.

-- Bill M. "People change, walnut doesn't" by Gene.

View Lazyman's profile

Lazyman

1444 posts in 1203 days


#6 posted 03-19-2017 03:41 AM

If you drew that drawing in Sketchup, you can use the protractor tool to measure the angles.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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jbay

1800 posts in 715 days


#7 posted 03-19-2017 03:53 AM

http://jansson.us/jcompound.html

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

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waho6o9

8010 posts in 2393 days


#8 posted 03-19-2017 04:08 AM

2 cool jbay, thanks

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runswithscissors

2545 posts in 1841 days


#9 posted 03-19-2017 04:08 AM

So is this a solid block, or a hollow pyramid (with thin panels_?

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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firefighterontheside

16740 posts in 1672 days


#10 posted 03-19-2017 11:55 AM

Good point. I assumed solid because that’s the easiest way to make it. Now that you say that and I re read the post, I think it’s supposed to be thin panels. I’m no help with that.

-- Bill M. "People change, walnut doesn't" by Gene.

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pashley

1043 posts in 3533 days


#11 posted 03-19-2017 12:40 PM

Yes, this is ⅜” panels, glued up, not a solid block.

-- Have a blessed day! http://newmissionworkshop.com

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htl

3063 posts in 975 days


#12 posted 03-19-2017 03:11 PM

Would it come out nicer cut solid, then veneer it, just a thought.

-- There's a hundred ways to do anything, alot depends on the tools at hand.

View squazo's profile

squazo

49 posts in 1461 days


#13 posted 03-21-2017 02:39 AM

here is how I would figure it out

I would cut an over sized triangle

then on a table draw a line that is 4 3/16” long and at 90 degrees to that the 2” line then

I would take a piece of scrap that is 3/8 thick and line it up on my lines and figure all the angles from there.

transfer the angles to the over sized triangle and blamo.

Im sure this was not much help but maybee you can get some ideas.

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jbay

1800 posts in 715 days


#14 posted 03-25-2017 04:56 PM

*

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

View pashley's profile

pashley

1043 posts in 3533 days


#15 posted 03-25-2017 05:38 PM

Jbay,

Please except my apology; I sincerely appreciate your help and thank you very much!

-- Have a blessed day! http://newmissionworkshop.com

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