For many interior molding situations such as baseboard and crown, etc. , you should not miter the inside corners. It won’t fit right and miters tend to separate in these situations. For inside corners, you should learn a technique called “coping. " This is not difficult (do a search for instructions).
If you’re using a non-45 angle, you’ll need to do some math. Don’t worry: it’s easier than it sounds. Use a calculator or the interactive circle on this page to find the sin and cos for the angle of the cut you’re making. Next, take your calculator and divide the sin by the cos. Take the resulting number and multiply it by the depth of your wood. The resulting number is how much extra space you’ll need.
When cutting a picture frame style cut, place the flat side on the cutting surface. When cutting a box style cut, place the flat side against the fence (or back piece of the cutting surface).
