I took the compound angles from SketchUp for Web for some slanted boards that will go on top of a pergola, but when I made the actual cuts it doesn’t end up right. The boards are leaning 22,5 deg, and measuring in Sketchup gives me a 42,7 deg miter angle and a 20,9 deg bevel angle. After some test cuts it seems the miter angle is good but the bevel angle is too large. In reality it worked at slightly less than 16 deg and I could confirm that by getting 15,7 deg in two different online compound angle calculators.
I’m probably doing something wrong in Sketchup, but I can’t figure out what it is. Any ideas?
You have to make sure you’re measuring the angles from the correct references. If you share the file it would be easier for us to show you how to make the measurement.
I can understand why it didn’t work real well, though. If you cut the top rails at 22° as you have in the model, the compound miter angle won’t be right.
Nice spotted, but 22° is just my mistake in the drawing for the top rails (I tried several different angles before settling with 22.5). The error is too small to have an impact in reality since it’s hard to make bevel cuts with more than about 0,5° precision.
I’ve solved the problem for this build through help from Compound Miter Saw Calculator which states 15.7° (a lot less compared to 20.9° from SketchUp), but I was hoping to be able to trust SketchUp for planning any future and more complicated projects and compound angles. Therefore I’d really like to get to the bottom of this and understand where things go wrong.
The angle should be from perpendicular of the miter cut, as per the angle on a power saw, Dave is showing the bevel at the end as a result of a compound cut
