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110 WORKING WITH METAL

What’s This about Heat Treatments?

When shopping for metal bits and pieces, you may come across references to how the mate-
rial was heat treated. Heat treating is used to enhance certain physical properties of the metal.
As heat treatments can affect the price of the metal, there’s no reason to pay for something
you don’t need. So you can be an informed shopper, here are the most common treatments
in a nutshell:
• Hardening strengthens the metal and literally makes it harder. The process also makes
the metal more brittle. Tools are commonly made of hardened steel, and the hardening
process makes it very difficult to cut or drill the metal.
• Annealing softens the metal and makes it more workable— a metal that is ductile or mal-
leable is easier to work with, usually because it’s been annealed. Copper is routinely an -
nealed, but many other metals, like aluminum, can be annealed, too.
• Tempering removes some of the hardness and brittleness of steel and in doing so makes
it even tougher. An example of a tempered aluminum alloy that you may encounter is
6061- T6, which has several times the strength of the same alloy untempered.
• Case hardening is a coating process for soft steels and allows relatively low- carbon steels,
such as wrought iron, to be hardened. It’s frequently used with steel to make tools.

G Hardening and tempering can be accomplished in the home shop, useful for the die- hard
combat robot enthusiast. The subject is beyond the scope of this book, but if you’re interested in
the concept, check your local library for a good tutorial on home metalworking.

Where to Get Metal for Robots

You’ll find most metals for robot building at these local sources. If they don’t provide the mate-
rials you need, try a Web search to locate mail- order suppliers of the metals you want:

Hardware and home improvement stores carry some aluminum and steel sheets, but
look for angle brackets, rods, and other shapes. See the section “Metal from Your
Home Improvement Store,” below, for more details.
Hobby stores sell aluminum, brass, and copper, in small sheets, rods, tubes, and strips. A
common brand sold by stores in North America is K&S Engineering. The metal is sold
in small quantities, which makes it more expensive, but more convenient. Read more in
“Metal from Craft and Hobby Stores.”
Metal supply shops that cater to welders are usually open to the public and offer all kinds
of useful metal. Many sell stock in large pieces, which you can have cut so you can get
it home in your car. Tip: Check out the “remnant” bin for odds- and- ends sizes.
Restaurant supply stores, most of which are open to the public, sell many aluminum and
steel materials. Look for spun bowls, cookie and baking sheets, unusually shaped uten-
sils, strainers, and other items that you can adapt to your robot creations. Metal is metal.

Recap of Metals for Robotics

See Table 11-1 for a review of metals that are particularly well suited for the construction of
robotics. Each metal is noted with its common use, main benefits, and principle drawbacks.

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