Crown molding corners can be a real challenge for the novice. Any handyman can cut crown molding, but to cut 45-degree corners that will fit together without excessive space between them, that will take special equipment and special skill. Unless you've had experience making these corners you will probably need a few helpful tips like those below.
Step 1 - Cut Angled Corners
To cut angled corners you will need a coping saw. These saws are easier for a novice to use in cutting angled corners. If you don't have access to a coping saw use a power miter saw.
Step 2 - Choose the Right Molding
Before purchasing your molding, you should take into account which room you plan to install it in. Kitchens and bathrooms will be more humid than other rooms of the house. In these rooms, you should avoid using moldings made of MDF (Medium Density Fiberboard). Because these moldings come already primed, your using them will likely reduce the time required to paint them, once they are installed, but in more humid environments they are more likely to warp.
Step 3 - Measure for Molding Lengths
Use a measuring tape to figure the length of the first piece of molding, This measurement will represent the total length of the molding piece after it is cut, including the angled corners.
Step 4 - Cut Your First Measured Molding Piece
Set the miter saw guide to 45 degrees, then place on the saw surface the molding piece you plan to cut. Be sure to keep the molding piece pressed tightly against the saw table surface and the saw fence. If you allow it to move while being sawed it can ruin the corner angle.
Step 5 - Understand the Molding Position
The most confusing part of creating molding corners is understanding the relative position of the molding piece as it lies on the saw and as it will fit on the wall. It will lessen your confusion if you think of the molding edge that is pressed against the saw fence as the molding's bottom surface, and the molding edge that sits on the table surface as the molding's top surface. You'll also need to cut the molding in the right direction. To cut the molding for an inside corner, for example, the bottom edge of the molding should be longer than the top edge. For an outside corner, the top edge of the molding piece will be longer.
Step 6 - Cut the Molding Corners
Install a 10" blade on the saw, and when you are certain the molding piece is positioned correctly, mark the front edge of the molding. With your coping saw, make your cut outside of the line you've marked as the end of the molding piece. Cut as close to the line as possible, without cutting into the line. Move the saw slowly and carefully, so as to avoid splitting or chipping the wood. When both pieces of your molding are cut, you will be ready to attach them to the wall and fill the gaps between them with wood filler.