The success of our LM-1 and LM-2 models led us to develop the latest in our family of lap molds, the LM-3. This "Perfect Pitch" lap mold allows you to quickly make picture-perfect pitch laps for mirrors from 4" to 40" and above, with a single lap mold. It combines the smaller facets of our LM-2, with the larger mold dimensions of our LM-1, and adds a unique feature - a 10 degree pyramid angle to each facet. This improves the separation of the mold from the lap, and also extends the pitch lap service life. As the pitch squares begin to close in during use, the facet walls slowly steepen to 90 degrees, requiring trimming only after they have moved well beyond 90 degrees and threaten to contact each other. The 10 degree pyramid angle is also present in the outer edges of the lap mold; when used to make laps for large mirrors in "tiling" mode, this butts precisely against a previously poured pitch square column, assuring a perfect, seamless transition between lap sections.
Note that this lap mold is unlike older open-mesh "doormat" molds such as the one Edmund's used to sell. The "Perfect Pitch" lap mold has a continuous floor, which lets you lay it directly upon your mirror without risk of pitch sticking to the mirror. It also conforms directly to the radius of the primary mirror, reducing hot pressing to a minimum. A dimensional drawing of the LM-3 lap mold is shown below, together with the relative positions of the mirror, tool, and pitch.