Making precision crosscuts is most easily done with a drop saw, also called a miter saw. In conjunction with what is called a miter index, a drop saw can be counted on to make accurate angled cuts in wooden frames, trims and molding. Finish carpenters traditionally used a miter box with an attached miter saw to cut the wood for fine trim and crown molding. Precise angles were required, so a miter index was used that set the blade in the right position. Motorized miter saws or drop saws have largely replaced the manual version, but a miter index is still required for precision. This how-to describes the operation of a drop saw up to and including the use of the miter index.
Step 1: Measure and Mark the Wood
Measure and mark the trim or molding to be cut from the reveal line drawn on the jamb of the window or door to be trimmed out. Measure along the inside edge of the piece to be cut rather than the outside. Set the sliding bevel to the right angle (45º) and trace a line over the width of the trim or molding. Be sure to mark the line for cutting on the right face of the wood. Trim that lies flat against the wall is cut widthwise while molding along the edges of walls is cut lengthwise.
Step 2: Set the Blade Using the Miter Index
At the front of the drop saw is an adjustable toggle. Loosen it to release the blade and handle. Now it can be adjusted. Along the bed plate of the saw there is an index, 180 degrees of hashmarks with bigger lines representing the most commonly used angles. There is also a indicator line that rotates with the blade to let you know when it is correctly lined up at an angle. Once in place, tighten the toggle. Some miter indexes are found along the fence with openings in them at 15, 30, 45 and 90 degrees. Line up the blade with the 45-degree line and tighten the toggle.
Step 3: Secure the Wood
Hold the wood to be cut securely against the fence of the drop saw. Use your eyeball to position the wood in the approximate place. Without turning the saw on, bring it down to make sure the blade is aligned with the line. Whichever end of the wood is being used, align the blade with the edge of the line on the opposite side. Doing this compensates for the thickness of the blade.
Step 4: Make the Cut
Still holding the wood in place firmly against the fence and with your safety glasses on, press down on the safety button and depress the trigger. Bring down the blade in one continuous motion all the way through the wood, let it up and release the trigger.
You are left with a piece of wood with a precisely angled cut. Provided you measured the length correctly, it should fit perfectly in line to frame the window or door. When you cut the other end, make sure you set the 45-degree mark in the opposite direction so it creates a trapezoid.