Join Date: Sep 2009
Location: Coquitlam B.C. Canada
Using the "old" bosch miter finder (not the new one that's out now) use the reciprocal angle. Your wall is 92? use 88 deg. the saw setting will be 44 deg.
This is because the miter finder reads "zero" when folded up. If it read zero wide open then it would give you the correct number. I can't remember why this is though. Every corner is two angles, 90 + 90, or on your wall, 92 + 88. The new bosch apparently takes this into account, but I haven't seen one yet to confirm.
Think of it this way: 92 degrees is wider than 90 degrees, so that means that your cuts have to be shallower- hence 44 deg. (44 + 92 =180 deg)
OR 180 - 92 = 88/2 = 44.
so greater than 90 degrees? you know your answer will be less than 45.
Less than 90 degrees? your answer will be greater than 45.
I also use a rediculously huge saw, the milwaukee 12". It's got the digital readout to 1/10th degree, so its very accurate. This is not necessary though, if your saw has a decent scale you can eye-ball it pretty close.
I cut my crown nested, so I only have to worry about the one number, its way easier than trying to get the "tilt" on the saw anywhere close to what is required.
After a while you find short cuts - what ever happens to 90 degrees, I do the opposite. 92? ok that's two greater than 90, so I will use the number 2 less than 90, which is 88. cofusing! try it with some scraps for a bit, it makes sense after a while. It took me a few years to get that through this old noggin :D but then I'm left handed.... LOL
Go to the site compoundmiter.com Wayne Drake has a really good book on this subject.
I'm starting a job tomorrow that 4 contractors have refused- its a vaulted ceiling! that throw all the rules out! I went to my book (mentioned above) and that gives me the numbers. Also got a download from the same firm that has the math for doing this.
Oh! and cope!
Last edited by MrMac204; 12-12-2010 at 10:10 PM.
Reason: clarify confusing stuff