Hi All,

I need some help. I am trying to construct a hollow square pyramid frustum
using slabs. Top inside 1" x 1", outside 1.25" x 1.25". Bottom inside
4"x4" outside 4.25" x 4.25" The angle of the side to base is 60 degrees,
the slabs are cut with the top and bottom parallel and the sides at ~65
degrees.
In order to be square at the top and bottom, the adjacent sides aren't
square to each other and there in lies my problem.
I can't remember the way to calculate the bevel the edges of the sides so
that when two side are assembled they are square when looked at from the
bottom or top.
I knew this trick years ago from making micro wave horns but I can't find my
notes.
All help appreciated, a pointer to a web sight with graphics and forumlas
would be even better.
Kent

On Mon, 26 Jul 2004 19:24:46 -0400, "K Frazier"
wrote:

Hi All,

I need some help. I am trying to construct a hollow square pyramid frustum
using slabs. Top inside 1" x 1", outside 1.25" x 1.25". Bottom inside
4"x4" outside 4.25" x 4.25" The angle of the side to base is 60 degrees,
the slabs are cut with the top and bottom parallel and the sides at ~65
degrees.
In order to be square at the top and bottom, the adjacent sides aren't
square to each other and there in lies my problem.
I can't remember the way to calculate the bevel the edges of the sides so
that when two side are assembled they are square when looked at from the
bottom or top.
I knew this trick years ago from making micro wave horns but I can't find my
notes.
All help appreciated, a pointer to a web sight with graphics and forumlas
would be even better.
Kent

Try this. http://www.woodcentral.com/bparticles/miterangle.shtml For
more help, Google for "compound miter table".