Hints For Using Cerrosafe
By:
Mike
Watkins
Recently, we’ve fielded a lot of
questions on the Tech
Help Lines about casting chambers using Cerrosafe casting
metal. The following
is some information about Cerrosafe that Cerro Metal Products
has provided us
with.
 |
| 1 lb.
Cerrosafe
Ingot |
“The basic
ingredient
of Cerrosafe is bismuth. Bismuth is a heavy, coarse, crystalline
metal which
expands when it solidifies, up to 3.3% of its volume. When
bismuth is alloyed
with other metals, such as lead, tin, cadmium and indium, this
expansion is
modified according to the relative percentages of bismuth and
other components
present. As a general rule, bismuth alloys of approximately 50%
bismuth exhibit
little change of volume during solidification.
Alloys
containing more than this tend to expand during solidification
and those
containing less tend to shrink during solidification.”
What all
this means for the gunsmith is that you can make chamber
castings using only
Cerrosafe and a few, simple hand tools. To make a chamber
casting, first clean
and degrease the chamber. Use a tight-fitting, cotton patch
that’s wrapped
around a bore mop or brush to plug the bore just ahead of the
throat. I usually
leave the cleaning rod attached to the plug until it’s time
to remove the
plug. Melt the entire bar of Cerrosafe in a heatproof container
that you can
easily pour the hot Cerrosafe out of. You can use a propane
torch or heat over
a hot plate or the burner of a stove. Cerrosafe melts easily at
158°-195° F. While the casting metal is still liquid, stir
very well,
skim off the dross and pour your chamber. The real trick with
Cerrosafe is not
to overheat it. If you heat the solid slowly, and keep it within
the required
temperature range, you shouldn’t get any dross.
Note the
time the casting was poured. The casting will take only a very
short time to
solidify, usually within a minute. Wait 30 minutes and then
remove the plug
from the bore. Turn the muzzle upward and the casting will fall
from the
chamber. At 30 minutes after initial solidification, Cerrosafe
shrinks
slightly, so removal is very easy. Allow the new casting to cool
thoroughly
then measure the casting exactly one hour from the time it was
cast. The
casting will give you an exact measurement of the chamber.
Cerrosafe casting
metal can be used over and over. Remelt the entire amount
back together and
pour the Cerrosafe into a small mold of the appropriate size.
Always melt the
entire Cerrosafe ingot to make a chamber casting. For best
results, never cut
off, or use, just a part of the ingot.