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.
Here is a good free cad program. It's a 5 or so year old
version of Tubocad with no expiration date.
If you know how to do what you want with drafting tools,
then it will be easy in Turbocad.
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
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.
I've added a form to my website that does this for you:
(it accepts either angles or rise/run)
The OP's results would be:
Sorry, I round to only one digit after the decimal ;-)
[feel free to post the CGI's url as responses to future requests for
such math ;]
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.
Reawakening long dormant areas of my mind. And loving it.
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?
On Fri, 31 Oct 2003 13:51:59 GMT, "Robert Smith"
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