Learn how to use a compound miter saw to create crown molding.
In recent years, two woodworking trends have helped fuel each other -- the popularity of crown molding installations and the proliferation of compound miter saws.
One of the major challenges in using a compound miter saw is visualizing how to position the crown molding on the saw before you make the cut. To overcome this, you'll make four templates -- one for each of the basic saw positions used for running crown around a flat ceiling.
You'll need an accurate protractor -- preferably with legs at least 18 inches long -- for each outside corner in the room and for inside corners that are not exactly 90 degrees. Because you'll cope an inside corner against a square-cut piece that butts into a corner, you don't have to be so finicky about the inside angles. Back-cut the cope and you'll easily fit corners.
If you have 52/38 crown molding (see Understanding the Spring Angle), set the miter at 31.6 degrees left and bevel the blade 33.9 degrees left. Some compound miter saws have a miter stop at this setting. If you're working with 45/45 molding, the miter angle is 35.3 and the bevel is 30 degrees. Slice apart the LH cope/RH miter templates.
Measure an outside corner with your protractor, holding it where the bottom of the molding will hit the wall. A protractor with long legs will give you a more accurate reading because it will measure well beyond the corner. Because that area was formed by the drywall finisher who applied the compound at the corner, its surface may not truly represent the angle between the walls.
Lock the protractor's angle (in this case, by turning a small brass knob). Check that the setting didn't change when you turned the knob, then read the angle on the protractor. Refer to the Crown Molding Cutting Angles chart for the spring angle of the molding you have -- either 52/38 or 45/45. Set your bevel setting to the angle listed in this chart or the chart that came with your compound miter saw.
Place the appropriate template sample for the right- or left-hand miter onto your saw table, then set the miter to match the direction of the cut on the template. The exact miter angle you set will be the one you found on the chart in the last step. Observing how the molding is oriented on the table (bottom or top toward the fence), slide the template away from the fence and place your molding in the same relative position. Move the template out of the cutting path, then make the cut.