Originally Posted by
Stan Clayton
Sure! The pattern in the photo above is too rough surfaced to pull a mold from. To get it ready, I mix up epoxy tooling dough (like J.B. Weld, except in 5-gallon buckets) and roll it out in quarter-inch-thick strips. I also mix up a cup of slow adhesive epoxy resin. To bond the dough to the pattern, I paint a layer of the resin on the surface, then lay the strip of dough on top of the painted part. The epoxy in the resin and in the dough are compatible, and since the resin soaks a bit into the pattern, it bonds the two together.
The dough hardens rock-hard, and is specially formulated to be machined. The pattern is then re-machined with a very small step-over to produce a smooth, hard finish that needs only light sanding to be ready to pull a mold from.
Hope that helps.