The accurate installation of cove moulding trim at corners is a matter of defining the angles for precise cutting of mitred joints. Whether cutting for a typical 90-degree corner or an obtuse angle, understanding the method will make certain that every joint at two pieces of cove moulding will be perfectly matched.
Place the piece of uncut cove moulding in place and mark the point at the rear edge, where it meets the corner of the wall.
Use the mitre saw’s angle scale to move the angle of cut to 45 degrees and lock in place.
Put the piece of cove moulding to be cut against the mitre saw fence, with the square side against the fence and the cove shape facing you. Position the piece so that the point marked in the first step will be the short length of the cut angle. Cut the piece at the line.
Reposition the mitre saw table to the same angle on the opposite side and repeat Steps 1 through 3 for the cove moulding piece on the other side of the corner.
Position both pieces of cove moulding in place to insure proper fit of the corner joint and install.
Set a bevel square against the corner, pressing the two arms of the square tight against the two adjacent wall surfaces at the corner. Tighten the square’s locking screw to set the bevel square to the angle of the corner.
Position the bevel square’s handle against the straight base of a protractor, holding the inside corner point of the bevel square at the centre point, and the square’s adjustable arm touching the degree scale of the protractor. The angle reading on the protractor's curved scale defines the angle of the corner.
Divide the angle determined in half. For example, a 45-degree angle divided in half results in two 22 1/2-degree angles or a 60-degree angle divided in half tells you that it takes two 30-degree angles to mitre that corner. This basic method can be used to determine any angle required for any corner.
Adjust the mitre saw to the angle defined earlier and trim the corner following the method described in the first section of this article.
Precutting the corner angles on pieces of scrap moulding to test the mitred joint can save material and insure you have set the proper measurements.