Hi, Welcome.
360º ÷ 6 sides = 60º ÷ 2 = 30º each side of the joint.
Your 6 sided box will have 60º degree corners. Each side of the joint will be cut to 30º which will give you a 60º corner. How wide is the base of the glass pyramid? You want the top of the box to match the bottom of your glass pyramid so it looks like one continuous line? If so the box will be 20" tall when finished + the 4" glass to you a 24" finished height.

You can draw it out on a piece of scrap wood or large paper. Without knowing the width of the base of the glass you have you can draw two parallel lines 24" apart. Draw another parallel line down 4" from the top line. This is the height of your glass pyramid. Use a framing square & draw a centerline that connects the top line & the bottom line. On the centerline that is 4" down center the width of the bottom of the glass pyramid. Draw a line from these two points to the center mark on the top line. This should be the size of the glass pyramid.

Now take a straight edge & line one end up with the top centerline mark & move it across the bottom line until it lines up with the line for your 4" glass pyramid. Then draw a continuous line to the bottom. Do this on the other side & you should have a full size drawing of the sides.

Now your top & bottom of each side would have to be mitered to sit flat (parallel with each other) if it matters to you but without knowing any other measurements for the taper (base width to zero center point top)?

 

Hello,

Here is a simple calculator for cutting polygons.

http://myweb.cableone.net/mikec/wood/polycutcalc.xls

Mike

 

Hello,

Here is a simple calculator for cutting polygons.

http://myweb.cableone.net/mikec/wood/polycutcalc.xls

Mike

Hi Mike
did you make calculator? If so there are also two outside diameter's used in stave construction depending on desired need. One is outside center of each stave & the other is point to point. Could these be added?

 

Hi

A real easy way is with one router bit...the math is all done by the bit..see video.

http://www.mlcswoodworking.com/orderstatus/html/smarthtml/graphics2/TM58multiglueset.pdf
MLCS Euro door, door lip, finger pull, drawer lock bits, glue joint router bits

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Hi

A real easy way is with one router bit...the math is all done by the bit..see video.

http://www.mlcswoodworking.com/orderstatus/html/smarthtml/graphics2/TM58multiglueset.pdf
MLCS Euro door, door lip, finger pull, drawer lock bits, glue joint router bits

=======

Bob that works for a round cylinder on square stock but you have to cut the tapered pieces first before using the bit. He wants to match his glass pyramid on top. Either way you still need to know the finished diameter to know how wide your 6 parts need to be.

 

Hi

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I've found an error in my stave calculation formula.

Mike

 

Looking in my Practical Math Dictionary I believe the radius that measures from the center of each flat is called the "radius of inscribed circle". The radius that measure from point to point is called the "radius of circumscribed circle"

 

G'day N/A

Welcome to the router forum.

Thank you for joining us

 

The formula for calculating the stave width has been fixed.

http://myweb.cableone.net/mikec/wood/polycutcalc.xls

Mike

 

Thank you for the spreadsheet, I'll be using it!

 

Hi ltrivett,

You are welcome.

And yes, please post pics when you can.

Mike

 

I'm amazed at the wealth of information I've received from one simple post. I truly appreciate all the help I've gotten from the good people of this forum. As soon as I get a chance to cut these pieces, I'll see if I can post some pics so those who've helped can see the fruits of their assistance! Thank you all so very much.

 

To make my tapered lighthouse sides, I first built a jig to cut them.
It is as tall as the sides will be, and has 2 steps in the bottom edge which are (c) 1/2 the distance of the bottom edge (b) minus the top edge (a).
I cut the sheet stock on the table saw with the sheet on the first stop, turn that piece over, place on the second stop, and make the next cut.
Very simple to do. After making the first cut, just turn the stock over and continue cutting the remaining pieces.


I then use the router table with a chamfer bit to form the correct angle.
In my case with an 8 sided LH, I use a 22.5º bit. In your case, a 30º bit.

 

Well...

Thanks for sharing the calculator to cut the 6 sided polygons..
Its very useful for all of us...

 

You are welcome Anora.

Mike

 

Whatever you do, cut your first attempt out of stiff cardboard or cheap plywood, and see how it comes together. Then you can make adjustments as necessary before you get into real wood.