Calculate right angle on sloping surface

[Wikingen]

Hello,
I am going to make a shelf with sloping surfaces. The surfaces slope at 20 degrees and are to be mitered around a corner (90 degrees). At first, I thought it was just a matter of setting the saw at a 20-degree tilt and a 45-degree miter. But no, in order to get the miter on the sloping surfaces, it ended up with a miter of about 41.5 degrees. It works, but I would like to know the formula to calculate it exactly.
Anyone?

 

[norrbottenstorpet]

A sketch or picture, I might be tired, but I didn't follow what you did?

 

[Wikingen]

Hello everyone!
Found this on the forum after a while: http://www.byggahus.se/forum/altan-uteplats/152959-gera-lutande-overliggare-hur.html

I've received answers but would love to know the formula for the calculation and also how to input it on the calculator ;-)

 

[vem_jag]

I think this link http://www.youtube.com/watch?v=_CRJsn_pQ7Q can give you an idea of how you can solve your problem. In your case, it's just about calculating on a 4-sided polygon. If you follow the link to his website, there are calculations for more angles.

 

[Granngubben]

Hello everyone!
Found this on the forum after a while: [link]

Got a response but would like to know the formula for calculation and also how to input it on the calculator ;-)

The formula for "angle saw table" (in the table in post 23) is:

where alpha is "slope overliggare"

 

[Matte_Nörden]

The formula for "saw table angle" (in the table in post 23) is:
[image]
where alpha is "railing slope"

I have not read the thread it comes from, but a quick look at the formula suggests it can be simplified somewhat. Remove the two in front of Cos squared and replace sin squared with one (the trig identity).

 

[Matte_Nörden]

Same formula, but in my opinion a slightly nicer appearance.

 

[Stefan Bengtsson]

The formula for "saw table angle" (in the table in post 23) is:
[image]
where alpha is "railing incline"

Doesn't the angle between the pieces matter? For example, if you're making a 4-sided or 6-sided shape?
Or am I mixing up the terms "saw table angle" and "saw head angle"?

Or do I just simply have my usual bad luck when I think?

 

[ullberg]

Does the angle between the pieces not matter?

If I've understood the references correctly in this thread, it's hardcoded in this case (90 degrees), Mikael L mentioned something about it. But sure, otherwise that angle is highly relevant.

/U

 

[Granngubben]

Haven't read the thread it comes from, but a quick glance at the formula suggests it can be simplified somewhat. Remove the two in front of Cos-squared and replace sin-squared with one (the trig identity).

Thanks! It became a bit simpler.

The formula applies to corners with 90 degrees.

 

[Stefan Bengtsson]

If I've understood the references correctly in this thread, then in this case it is hardcoded (90 degrees), Mikael L mentioned something about it. But sure, otherwise that angle is very relevant.

/U

Aha. As usual with bad luck then...

 

[ullberg]

Aha. As usual with the bad luck then...

Well, I would personally call it observant, but if you have a need to belittle yourself then that's none of my business...

/U

 

[Matte_Nörden]

The topic states that a right angle is being discussed.

 

[fahlis]

Well, it is quite clear that it is the right angle that is being sought.

 

[Matte_Nörden]

On my device, the title is spelled with one t. CORRECT.