Any strong feelings out there?
I was thinking along the lines of a simple way to determine the proper bevel/angle if I wanted a box 12" square at the bottom, 16" square at the top and 20" tall.
JP
******************* Trigonomically challenged.
Here is a good free cad program. It's a 5 or so year old version of Tubocad with no expiration date.
Rico
Look for the freeware program called "Polycut", its great for what you want to do. Let me know if you can't find it and I'll try to send it to you.
Ed Angell
Assuming you are going to use a compound miter saw to cut your parts. Here is a formula that will give you the miter gauge setting, and the head angle for any number of sides on any angle you choose.
First, we need to find the angle of your side pieces. This angle is from the horizontal up to whatever angle you want. In other words, if the sides were vertical the angle would be 90 deg. In your case the sides tilt out 2" in
20". So to find your angle take 20/2 this is the tangent of the angle. Which equals 84.2894 deg.Now to try and make the formula easier to understand we need to define two variables. The number of sides will be in variable "s". The angle of the sides, which we just calculated will be in variable "b" Just plug the correct values in this short formula and you will have your answer
a=360/s x=arctan((cos b)*tan(a/2)) y=arcsin((sin b)*sin(a/2))
The "x" value will be the angle that you set your cross cut to.
The "y" value will be the angle that you set your saw blade to.
In your case the cross cut angle will be 5.6824 deg. and the saw blade will be on a 44.7164 deg. angle. Of course you can round those numbers off, I've been a machinist for 28yrs. and always think to four decimal places.
Mmmm... math.
I've added a form to my website that does this for you:
The OP's results would be:
Cool! I remember actually doing OK in trig as a kid, but I haven't had need to use it in.....hmmm...*ever*, actually!
Also thanks to those who pointed me towards free calculating software.
JP
*********************************** Reawakening long dormant areas of my mind. And loving it.
That helps, right?
-Phil Crow
What timing!!. I'm in the process of trying to throw together a little bed for the resident feline. This is my first attempt at building a "box" with angled sides, and I quickly discovered that I had no clue as to determine what angles the compound cuts should be made. Thanks for the timely info.
I do have a question though. When rounding from the nearest 10,000th to the nearest 16th (which is about the most precision I can hope to attain with my limited experience), do I round both angles in the same direction? For example, if I round the miter angle up, should I also round the bevel up, or should I round it down for best results?
Thanks Jim
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