Tech EXPO 2017 The Hot Wire Miter Saw Exhibit No. 3 By LukE Hadsall Oklahoma City University F or a recent production of the opera Don Pasquale, the scenic designer wanted a largescale crown moulding that was to be custom cut by a local foam vendor. We had worked with foam mouldings frequently in the past, but this new profile was too large to cut on our 12" miter saw. It was 14" tall and 8" deep. I had to find a new way to cut this large profile cleanly and accurately, as there were several miter joints to be made at varying angles. My solution was to build a miter saw that uses a hot wire to cut the Styrofoam (Figure 1). I liked the dust-free benefits of the hot wire. The first thing I designed was the cutting bow of the saw (Figure 2). I figured that giving it the cutting capacity of a 16" tall by 12" deep block of foam at a 45-degree angle would be sufficient for the next bigger and better design. With a little modeling in Vectorworks, I found that the throat of the bow needed to be 16½" tall and 20" deep. Mounting points with pivots were found in the modeling and full dimensions were determined to fabricate the bow; it was made from 1" 16-gauge steel box tube. Pieces of 2" angle iron were used as the pivot mount (Figure 3). A handle was fashioned from a scrap piece of hardwood. Figure 1 - Hot wire miter saw Now, it was time to move onto the table. The saw table was made from two layers of ¾" BC ply, a base (Figure 4) with feet, and a table top (Figure 5), which was spaced apart by ¾" ply spacers (Figure 4). The key to the function of the saw is the miter arm (Figure 4). This is made with another piece of ¾" ply that the cutting bow mounts onto. It is sandwiched between the base layer and the table top. Spacers are laid out to allow the miter arm to pivot 45 degrees left and right of 0 degrees. Of course, right after I cut these parts Figure 2 - Cutting bow Biennial Theatre Technology Exhibit 2017 13