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Chapter 2 Materials: How to Choose and Where to Find Them 39

Although we’ll cover different types of metal here and talk about finding the raw
materials, don’t discount sets like Erector Set and VEX Robotics Design System for
structural metal parts that are easy to configure. 80/20 Inc (www.8020.net/) and
Item (www.itemamerica.com/) sell grown-up versions of these configurable structural
systems, and MakerBeam (www.makerbeam.com/) is an emerging open hardware
version of the same.

Steel
Steel has excellent strength, but this comes at the expense of high density. Out of the
materials we’ll cover, steel is one of the more difficult to work with in its raw form
because drilling holes in it or shaping it takes patience. However, it’s great for screws,
shafts, and bearings, and as sheet metal.

Steel is a mix of mainly iron and carbon, with other elements like chromium, sulfur,
and manganese thrown in to create different combinations of strength and other
material properties. It conducts electricity and heat well.

Stainless steel resists rusting and is generally not magnetic, but it is difficult to sharpen.
Plain or carbon steel will rust, but it is easier to sharpen, so it is often used to make
cutting tools.

If you go to mcmaster.com and type “steel” in the Find box, you’ll get a screen that
shows a bunch of different shapes, dozens of alloys, over a dozen finishes, and
something about specifications. So how are you supposed to make sense of all this?
First, realize that you don’t need to find the perfect material—just something that
satisfies your criteria. As a rule of thumb on McMaster, start with the characteristics
that are most important to you, and then keep narrowing down the options until you
reach a manageable number of options.
Let’s assume you’re looking for some thin, steel sheet metal you can bend and drill
holes in for an automatic electro-mechanical toilet paper dispenser you have in mind.
In this case, you start by choosing the Sheets, Bars, and Strips icon. You don’t want
anything fancy, so choose Plain on the next screen under Type. You also think you
want something about 12 in long, so choose 12 in the Length section, but you’re not
picky about the other dimensions.