I have been tinkering with casting diamonds and other heat
tolerant stones in wax for a while now and having good success and
saving tons of time channel setting. Although, I have a couple of
questions for those of you who may do it on a regular basis. I am
using the long, low temp burnout cycle and using vacuum to cast.
The max temp I have gone up to is 1100F. The castings come out
rather dirty compared to conventional castings due to the lower
burnout temp. Thankfully, I have a magnetic pin tumbler to aid in
the finishing process. I don’t think I would cast with stones
without one. I haven’t had a big problem with shrinkage porosity,
but I have learned (for me) it is better to sprue on a button
rather than a tree. I seem to get some incomplete castings when
sprued on a tree. Could this be overcome by centrifugal casting
rather than vacuum? (I would like to get more than three or four
models in a flask) Would the turblence exerted by the centrifuge
cause the stones to break loose from the investment?
I am adding 5% boric acid to the investment mixture and it seems
to be crystallizing somewhat excessively. I have heard that by
adding boric acid to the investment, one can safely go up to 1250F,
but I havent had the guts to try it yet.
Has anyone successfully gone to this temp? Any advise or help would
P.S. Alan Revere, if your reading this,I love your book, but where
in the world do you find the large round edge joint files at? I
can’t seem to locate them.