cutting corners

“Turning the corner” is easily the most challenging part of any moulding installation or repair. It helps if you aced geometry in high school. For all others, learn to use a miter box, preferably one with a clamp. More experienced? Upgrade to a compound m

A miter box is a three-sided wood or plastic tool with open ends, which allow pieces of moulding or millwork to slide into position. It’s used with a backsaw, a rectangular saw with a reinforced spine that keeps the blade rigid. The saw fits into vertical slots in the miter box, set at the precise 45 or 90 degree angles needed to cut miter joints. You’ll need to cut a host of them if your job includes areas where the moulding turns at an outside corner.

To miter trim at an outside corner, cut two pieces of moulding at mating 45-degree angles. Fit together to form a tight right angle. It’s OK if there’s a slight gap at the back of the joint; it’s the “show” side that’s important. For mouldings to be installed flush (resting on the surface of the wall), nail the two mitered sides together with small finishing nails. If the moulding is sprung (installed at an angle to span perpendicular surfaces), glue the joint together. At inside corners, use a

coped joint for a better fit. (Wellfitted miter joints and coped joints end up looking the same.) In woodworking, coping refers to removing the bevel from a mitered piece of moulding: actually cutting the negative shape of the profile on a piece of trim. The traditional method is to cut away extra material with a

coping saw, a D-shaped metalframe saw with a thin blade held under tension. To make the first part of a coped joint, cut a 90- degree end on one piece of moulding and butt it into the corner. Miter the second piece of trim at 45 degrees for an inside miter. Then use the coping saw to remove excess material on the back of the mitered moulding.

To make the cut, first shade the leading edge of the moulding profile with a pencil. Hold the moulding at the correct angle (how it will fit against the wall), then tilt back slightly. Saw through the wood along the leading edge at 90 degrees, following the penciled line. Since the leading edge is set at an angle, the thin, narrow blade cuts away enough material behind it so that the moulding can fit against (and slightly on top of) the mating moulding. Test the coped moulding against the piece already in place. Get a perfect fit by smoothing any rough edges along the coped cut with a wood file and sandpaper.

Alternatively, scribe the profile of the first moulding onto the second one, using a compass fitted with a pencil. Set the compass to the width of the lumber. Butt the boards at a right angle, and draw along the joint to scribe the profile on the second piece. Use a coping saw to cut along the line. Now it should fit tightly against the first board. Prefer power tools to hand saws? Cut a small scrap piece of moulding in the correct profile and use it to make a tracing on the second piece of moulding. Then cut away the excess material from the back with a jigsaw.