The best way to cut crown molding is with a miter saw. Ryobi make high-quality saws, they are reasonably priced and are a great choice for this job. You couldn't ask for a better tool to do the job, in fact. To fit crown molding, it has to be cut with the utmost accuracy. The trick is to make the two contact surfaces—the piece that sticks to the ceiling and the piece that sticks to the wall—equal exactly 90 degrees. The crown molding will look half-baked if it doesn't. Usually crown molding has a top angle of 52 degrees (that's the bit on the ceiling) and the bottom angle (the bit stuck to the wall) is 38 degrees. And of course, that equals 90 degrees.
Lay the molding flat on the miter table. The broad back should be flat on the surface and against the fence.
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Set the bevel angle at 33.85 degrees.
Set the miter angle at 31.6 degrees either right or left depending on the cut. For a left side inside corner, the top edge of the molding goes against the fence and the table is set right at 31.62 degrees. Save the left end of the cut. For a right side inside corner, the bottom edge of the molding goes against the fence. Set the table left and save the left end of the cut. For a left side outside corner, the bottom edge goes against the fence. Set the table left and save the right end of the cut. For a right side, outside corner, the top edge goes against the fence, the table is set right and you save the right end of the cut.