Page 207 - Build Your Own Combat Robot

Build Your Own Combat Robot
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Precipitating-hardening stainless steels are particularly useful for high-strength
applications after heat treating. Alloy types 17-4, also known as type 630, and
15-5 are the most popular alloys in this group. One of its greatest uses is for
springs, but it also finds uses in gears and shafting. It is available in round stock from
3/16 to 4 inches in diameter.

Cold-Rolled and Mild Steel
Standard cold-rolled steel is frequently used in robot construction, especially in
combat robot–style machines. This can be as extruded galvanized 1011 angle used
for base or weapon construction, or it can be used as sheet stock for various appli-
cations. Alloy 1018 is probably the best steel for welding and machining. Plain
steel, if unprotected, has the bad habit of rusting, even in air. It is harder to machine
and saw than aluminum, but it is stronger for most applications.
Most of the stock cold-rolled steel is not galvanized and is ideal for welding.
These alloys are also prone to rust, which can cause you a lot of grief after the robot
is completed. After your robot structure is completed, whether by welding or by
nut and bolt fasteners, it is a good idea to sandblast the structure and immediately
coat it with a preservative such as anodizing or a thin plastic conformal film. This
will protect the surfaces and allow quick and secure electrical ground connections
on parts of the structure, providing the coating is removed at the electrical point of
contact. Sandblasting is particularly important before welding, and further hand
filing may be necessary to prepare the surfaces to be welded.
Most of the softer steel alloys such as cold-rolled steel are easy to machine,
though not quite as easy as aluminum or brass. Slower drill speeds are recom-
mended, which can be found in most shop handbooks, such as the Machinery’s
Handbook, or in the lids of many drill indexes. Keep the operation well lubricated
with a good-quality cutting fluid. You should take care to feed drills, mill cutters,
and saw blades slowly to the metal. As mentioned earlier, always use a good pair
of goggles or a face-mask when machining any metal.

Brass

Brass is another alloy that has useful applications in robotics, particularly in
smaller machines. Most brass alloys are easy to machine. Alloy 260 sheet stock is
readily available in sizes up to 24-by-96 inches, and in thicknesses from 0.10 to
0.250 inch. Alloy 360 is another brass alloy that many metal supply houses carry.
It is also called free-machining brass, and, as the name implies, it is best for ma-
chining of small parts, fixtures, hubs, and similar items.
Brass also has an excellent property of being able to be brazed or soldered by
simple, easily obtainable home shop tools. The low-cost, Bernz-o-matic–style
hand torch can be used to braze brass (and bronze fittings) to similar alloys. The
use of a larger Presto-lite torch might be needed to braze larger sheets of stock
that carry the heat away too fast. A large soldering iron or soldering gun can be