Lead Alloys
There are two general types of lead alloy, “soft lead” (mostly
pure lead) and “hard lead” (an alloy of lead and a harder
metal.) Pure lead melts at 621 degrees F. and has excellent pouring
characteristics at 700-800 degrees. A hard lead alloy may solidify
too quickly and require more effort to mold good parts.
SOFT LEAD
Soft lead can usually be identified by pressing or scratching your
thumb nail into it. If it scratches easily, it is probably soft
lead. If you can’t scratch it at all or only with pressure,
it is not soft lead. Since soft lead has a relatively low working
temperature (700-800 degrees for most applications), it is easy
to use. Small jigs and sinkers, as well as spinner jig lures, are
much easier to cast when using soft lead. Soft lead is a necessity
for use with bendable type sinkers such as split shot or pinch-on
sinkers.
HARD LEAD (Tire Weights, etc.)
Because of its molding difficulties, the use of hard lead is not
recommended in Do-it molds. Hard lead refers to a lead alloy that
has one or more other metals added to make a metal that is harder
than pure lead. The other metals can cause the alloy, when poured
into a mold, to solidify or “freeze” at temperatures
where pure or soft lead is still fluid. Consequently, more heat
or a faster rate of pour may be necessary to get complete castings
with hard lead. The chief appeal of a hard lead alloy for sinker
and lure making is that it can often be purchased at less cost
than soft lead. This advantage can be offset by difficulty in molding
the metal. The most common source of hard lead is used wheel or
tire weights. Since the main function of wheel weights is weight,
they often contain a lot of tramp elements. Wheel weight compositions
vary widely. If you acquire hard lead, remember that it will likely
require more experimentation and effort than soft lead to pour
complete castings. It may work well for some medium and large sinkers
and lures, but avoid its use in the more difficult to mold small
jigs and spinner baits. Do not use hard lead to make sinkers like
split shot or pinch-on types. These sinkers must be easily bendable
to work correctly. A hard lead alloy will make these sinkers too
stiff to bend.
Best molding results will be obtained using soft lead or a lead
alloy that is at least 98% lead. Following is a listing of various
types of lead and their approximate percentages of tin or antimony.
Commercial Pig Lead - 99.6% lead; Cable Sheathing - 98.5% lead;
Battery Lead - 90% lead and 10% antimony; Plumbers Solder - 67% lead
and 33% tin; Wheel Weights - (varies) may contain anything from aluminum
to zinc, in addition to antimony and lead; Type Metal - 82% lead,
15% antimony and 3% tin.
Effects of other elements to a lead alloy:
Antimony: Adds strength
and hardness. May cause premature solidification, wrinkles or other
molding flaws. Avoid metals containing antimony.
Zinc: Makes a lead alloy sluggish, limits its ability to flow and
requires a higher casting temperature. It can cause roughness, porosity,
voids and a grainy or frosted appearance on castings. Avoid metals
containing zinc
Aluminum and Iron: Effects castings the way zinc does. Avoid!
Tin: Adds ductility and strengthens lead. Tin melts at a low temperature,
449 degrees F., and generally improves a lead alloy. With some experimentation,
pure tin can be used to make lures and sinkers. Tin is an expensive
metal, but has no known environmental or health risks. A tin object
will weigh only 2/3 that of the same object made of lead. Example:
a 3/8 oz. lead jig will only weigh 1/4 oz. if made from pure tin.
Tin could be an attractive lead substitute if it was not so expensive
and difficult to obtain.
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