Cutting crown moulding laying flat

Calculating angles properly. April 2, 2002

I have recently purchased a sliding miter saw. The manual tells me what degree to set the bevel and miter on to cut crown laying flat for crown cut on a 45 and a 38 degree and how to cut it on a 45 degree angle but it doesn't tell me how to cut a 221/2 degree or how to figure out the bevel or miter setting if the bevel on the crown is not a 45 or a 38 degree. Does anyone know a formula to figure out these problems?

Forum Responses
If you have Excel it can do all the functions. If you set the spreadsheet up right you can figure anything to a high degree of accuracy. Now if the walls and ceiling were straight and plumb you'd be all set.

You don't need to cut crown laying flat. All you have to do to cut crown mould (unless your crown is really big) is use a framing square and measure how far down the crown will come on the wall. The crown I make is 4.25" and it comes down about 3 inches but that can vary with the run. Then make a mark on your saw fence at 3" (or whatever your height is) and turn your saw to the desired angle and make your cut. In all my time installing crown, the only time I have seen it done laying flat was on some exterior crown that was about 12 inches wide and 3 inches thick.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
To calculate angle and bevel for cutting crown, while lying flat, to install on a 22 1/2 degree corner, I have found it easiest to use scrap to determine the angle and bevel of my cuts. Unfortunately, most ceilings, walls and corners are not square, level, or plumb, and I must adjust my cuts accordingly. For 22 1/2 degree corners, I usually have both bevel and angle set somewhere between 14 and 18 degrees. This can vary depending on wall, ceiling, and corner, and the accuracy desired.

Comment from contributor B:
On a 22 1/2 inside angle I cut the Crown laying down at 15 degrees on the table and 18 degrees on the blade.