"Scorsi" wrote in message
om...
Hello, I want to cast some fine pitch gears in a Silicone RTV mold. I
want to know what the toughest and/or strongest material is moldable
in silicone RTV that would also serve well to make well
detailed,resiliant and strong gears.

Probably some exotic graphite and A/B-cure epoxy.

If you want metal, spincasters have cast aluminum diecasting alloys in
silicone rubber. The rubber is a very hard, high-temperature version. It
doesn't last for many shots but it does work. It doesn't much resemble the
common RTV type that's used for low-temperature casting.

Look up spincasting on the web. One company that I knew of years ago, in
Mount Vernon, NY, used to sell the rubber and the casting machines. The
lower-temp, RTV mold rubber is used for casting zinc-based alloys, some of
which mave mechanical properties that are very similar to those of
medium-strength aluminum. The Zamak family of alloys (look into ZA-8) have
tensile and compression strengths on the order of 40 kpsi and good bearing
properties. Their only disadvantage against aluminum is their tendency to
creep. Under high loads, running continuously, the teeth eventually will
deform. But the gears probably will wear out long before that happens.

Good luck.

Ed Huntress