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47^ SHOP NOTES.
Soldering Fluids.
Add pieces of zinc to muriatic acid until the bubbles cease
to rise, and the acid may be used for soldering with soft solder.
Mix one pint of grain alcohol with two tablespoonfuls of
chloride of zinc. Shake well. This solution does not rust the
joint as acids are liable to do.
When soldering lead use tallow or resin for a flux, and use a
solder consisting of one part of tin and \ x
/
2 parts of lead.
Spelter.
Hard spelter consists of one part of copper and one part of
zinc.
A softer spelter is made from two parts of copper and three
parts of zinc.
A spelter which will flow very easily at low heat consists of
46% of Copper, 46% of Zinc, and 8% of Silver. When making
any of these different kinds of spelter, melt the copper first in a
black lead crucible and then put in the zinc after the copper
has cooled enough to furnish just sufficient heat to melt the
zinc, but not enough to burn it. Stir with an iron rod and
after the metals have compounded and the compound is still
molten, pour upon a basin of water. The metal in striking the
water will form into small globules or shot and will so cool,
leaving a coarse granular spelter ready for use. When pouring
the metal let a helper keep stirring the water with an old broom.
Alloy Which Expands in Cooling.
Melt together nine pounds of lead, two pounds of antimony
and one pound of bismuth. This alloy may be used in fastening
foundation bolts for machinery into foundation stones. In such
cases, collars or heads are left on the bolts and after the hole
is drilled in the stone a couple of short, small holes are drilled
at an angle to the big hole ; when the metal is poured in, it will
flow around the bolts and also into these small holes, and it is
almost impossible for the bolt to pull out.
Caution.—When drilling holes in stone, water is always
used, but this must be carefully dried out by the use of red-hot
iron rods before the melted metal is poured in. If this pre-
caution is not taken the metal will blow out, making a poor job,
and it may also cause accident by burning the hands and face
of the man who is pouring it in.
Shrinkage of Castings.
General rule
:
yi inch per foot for iron.
%6 inch per foot for brass.
In small castings the molder generally raps the pattern
more than the casting will shrink, therefore no shrinkage is al-
lowed. Frequently castings are of such shape that the pressure
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