# Help Calculating a compound angle



## Heinlein0311 (Jan 9, 2019)

Hey folks, I have a range hood project I'm trying to build for my house. I've built 2 frames that I need to attach with 4 legs that will be angled. The legs are what's throwing me off. The shape is essentially a rectangular truncated pyramid or I think the technical term is rectangular frustum. I know they will be compound cuts and I've used the calculator on www.jansson.us but I'm not making much heads or tails Of it. I believe the calculator is giving me the miter and bevels I need to join the edges together. That I'm not worried about at this point. I need help finding out what the compound cut is that I need on the 4 corner legs so that the 2 frames join up centered on each other. These I circled in red on the last picture. I've included pics with measurements and a pic of a range hood that I'm trying to replicate in shape, most times I can tell a better story with pictures rather than words. Any help is appreciated


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## AlaskaGuy (Jan 29, 2012)

I believe if you Google "*compound angle calculator*" you will find several.


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## jonah (May 15, 2009)

If I'm remembering my trigonometry, you'd need to find the inverse tangent (arctan) of the bottom angle. I can't read your writing in the front view there, but based on the side view, you'd have a right triangle with the bottom side being 5.25" and the opposite side being 24". Based on that geometry, the angle there is 77.66 degrees.

If the front view of the top box is 16.5" (I can't tell for sure), then the geometry there is an adjacent side of 8 inches, an opposite side of 24", and thus an angle of 71.57 degrees.

I used this calculator, FYI.


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## BroncoBrian (Jan 14, 2013)

I like the design you are going for. Are you set on a range hood? I'd prefer not having that monster in my face and going with a downdraft at the range (they are pretty effective) or nothing at all. I cook a lot and when I remodeled I did away with it. It was a good decision.


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## jonah (May 15, 2009)

I believe that means tipping your saw to ~12.3 degrees and rotating it to ~18.4 degrees should get you the right compound angle.


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## jerkylips (May 13, 2011)

> I like the design you are going for. Are you set on a range hood? I d prefer not having that monster in my face and going with a downdraft at the range (they are pretty effective) or nothing at all. I cook a lot and when I remodeled I did away with it. It was a good decision.
> 
> - BroncoBrian


Off topic, but I've heard people complain that the downdraft sucks too much heat from the burners & it takes longer for things to cook than it would with a traditional hood. Have you experienced that?


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## BroncoBrian (Jan 14, 2013)

> I like the design you are going for. Are you set on a range hood? I d prefer not having that monster in my face and going with a downdraft at the range (they are pretty effective) or nothing at all. I cook a lot and when I remodeled I did away with it. It was a good decision.
> 
> - BroncoBrian
> 
> ...


Not really with gas, most of them have 3 speeds. But I would imagine that is a problem with electric ranges. But I do not even use one anymore. Unless you burn something badly, there add little value. Plus if you are crushing it in the kitchen, you want the smell to stick around!


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## GR8HUNTER (Jun 13, 2016)

*THIS * is GREAT :<))


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## rwe2156 (May 7, 2014)

I would build a v-shaped jig to hold the piece and just cut one angle.


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## Heinlein0311 (Jan 9, 2019)

> I believe that means tipping your saw to ~12.3 degrees and rotating it to ~18.4 degrees should get you the right compound angle.
> 
> - jonah


Thanks Jonah, that's exactly what I'm looking for. Took me a Few minutes to understand what you were talking about but I absolutely see how you arrived at those answers. My main concern was at what degree to bevel and mitre but you answered that too and now I understand how you arrived with those figures. Now to get home and put it in action. Thanks again!


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## Heinlein0311 (Jan 9, 2019)

> I like the design you are going for. Are you set on a range hood? I d prefer not having that monster in my face and going with a downdraft at the range (they are pretty effective) or nothing at all. I cook a lot and when I remodeled I did away with it. It was a good decision.
> 
> - BroncoBrian


Well if I was to be completely honest, although I will make it functional and to code, it will mostly be for visual effect. I like big range hoods. I've got some sheets of copper I want to age and make some panels with it and trim it out in hickory to match the kitchen sinks and cabinets. I do have a venting feature now but my jackass kitchen designer and builder ( ahem *cough *cough, me) made a mistake and it was to late in the process to fix. So the story goes, I found a great deal on a pop up vent that goes behind the oven. So I bought it and than I bought the freestanding oven not realizing the pop up vent was meant for a cooktop. It was to late to return any of these appliances so I rolled with it. This mistake created about a 6" gap between the back of the oven and the vent rendering the vent fairly useless but guests love to push the button and watch it pop up….I covered my mistake with a nice piece of stainless.
My cooktop is electric and I've heard before that hoods can steal heat. We have some pendant lighting over the island where the oven is located and when we did a deep cleaning for Christmas some of the lights had a good amount of grease on them.


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## jonah (May 15, 2009)

Not sure what you're building the frame out of, but if it's not construction lumber I'd try it on scrap first.


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## BroncoBrian (Jan 14, 2013)

Greasy lights mean you are using the right amount of oil and butter!

Yep - for electric, the popup will take some heat. I prefer gas because I can see it and the adjustment is immediate. Done right, the wood/copper vent hoods are statement pieces - I am with you on that.


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## BlueRidgeDog (Jan 2, 2019)

I typically draw the item in SketchUp and can the measure the resulting compound angle…control the two angles and measure the resulting one, just as for a chair leg.


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## Heinlein0311 (Jan 9, 2019)

Ok so a complete stranger (hell of a guy) from another forum drew me up a 3D model of the range hood with my dimensions and calculated the angles for me. I believe they are pretty close to what was mentioned earlier. The second picture is a cross section view of the legs that will join the 2 frames. So to get this to work do I still tilt my blade on my CMS to 11.72 degrees and rotate it 18.04 degrees?


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## Heinlein0311 (Jan 9, 2019)




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## rwe2156 (May 7, 2014)

If you did it like I told you, you'd already be done…...........LOL


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## jonah (May 15, 2009)

They'd be different angles for the top and bottom, so you'd need to come up with the tilt and rotation for each separately. It looks like the bottom, for example, is 18.04 and 11.72 degrees. Keeping things straight in terms of which angle is tilt and which is rotation and how you lay the piece down is going to be a bit of an adventure.


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## Heinlein0311 (Jan 9, 2019)

> They d be different angles for the top and bottom, so you d need to come up with the tilt and rotation for each separately. It looks like the bottom, for example, is 18.04 and 11.72 degrees. Keeping things straight in terms of which angle is tilt and which is rotation and how you lay the piece down is going to be a bit of an adventure.
> 
> - jonah


An adventure it was but I was able to get it figured out


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## Heinlein0311 (Jan 9, 2019)




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## jonah (May 15, 2009)

Looks great!


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## jerkylips (May 13, 2011)

> I like the design you are going for. Are you set on a range hood? I d prefer not having that monster in my face and going with a downdraft at the range (they are pretty effective) or nothing at all. I cook a lot and when I remodeled I did away with it. It was a good decision.
> 
> - BroncoBrian
> 
> ...


I wish it was only if I burned something badly. We just built a house & it has the world's most sensitive smoke alarms. It's insane how little it takes to set them off, so I have to run my fan pretty much every time I cook.


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## Heinlein0311 (Jan 9, 2019)

Thanks for all the help, I consider the result a success


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