This mold is to make all of the parts of a headstock in a single operation, including molding in the headstock dowels. The grey 3D printed headstock model is in the center, and a hand-shaped Plexiglas lever model is on edge on the right. The cavities on the left are for the headstock mount, which hides the lever mechanism and guides the strings over it. The front side of the mold is hinged, and has built into it the jig for precisely aligning the headstock dowels which are molded right in with the headstock body. Here the dowels are stainless steel for making the mold, however once the mold is made, the dowels can be anything ¼” in diameter. Carbon-fiber pultrusion is favored for the dowels because of its great strength and light weight.

After the mold box is made, the next step is to half-fill the box with artist’s clay and embed the part models in it up to a selected “parting line”. The clay will later be precisely replaced with silicone forming the bottom cavity of the mold, so great care is take to shape it just the way you want it especially at the parting lines. The big round-head hex nuts are indexing features for precisely aligning the two parts of the mold. Numerous dimples have been put in around the edges of the parts to serve as additional indexing features. The thin brass tubes are to serve as overflow reservoirs for excess epoxy.

The next step here will be to fill the top half of the mold with silicone poured through the large hole in the upper right corner of the lid. Any bubbles in the silicone will float up away from the model surfaces. After the top half of the mold has set, the mold box is opened, parts are removed, and all of the clay is scraped out. The part models are then embedded into their cavities in the silicone on the lid, the box is inverted, and silicone is poured into the mold box through a large hole like the one seen in the lid here. With the mold box being inverted as the bottom silicone cures, any stray bubbles in the silicone again float up and away from the mold surfaces. When all the silicone is cured, the mold box is opened, the part models are removed, and you are ready for business. It costs a bit more, but you can get molding silicone which is transparent so, if you have a transparent mold lid line the one above, you can watch what is happening on the inside after the mold is closed.