Page 60 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 2 Materials: How to Choose and Where to Find Them 41

NOTE The naming schemes for alloys of most metals (aluminum 6061 and
7075, 303 stainless steel, and so on) are confusing and not necessary to
understand or memorize. I’ll mention the most common alloy names, but
other than those, just read the descriptions of the material options you have
once you have narrowed down your options using other variables that are
important to you. McMaster often includes suggested uses in the descriptions,
like “excellent for sheet metal work,” “use for gears,” or “light structural
applications.” Follow that advice, or give the store you are ordering from a
call for help with selection.

Aluminum extrusions are made by pushing hot metal through a shaped orifice, just as
you did with the Play-Doh Fun Factory when you were little, only the metal is heated
to a much higher temperature to be formable. Extrusions can be flat bars, L-shaped
angle stock, or C-shaped channels.

Shelving standards (the rails you can nail into a wall, and then attach brackets and
shelves to) are readily available at home-improvement stores and can be used as
structural components. Aluminum angle and shelf brackets are good for mounting
motors and joining pieces together.

Aluminum is a good conductor of heat, but it’s a poor conductor of electricity relative
to copper.
Copper
Copper is a good conductor of electricity and very cheap, so it’s used a lot in wires,
printed circuit boards, and other electronic equipment. It is also used extensively in the
plumbing industry. Copper tubes can be assembled by brazing (see Chapter 3) to
create small art pieces, sculptures, or stands. Copper is relatively soft, so you will rarely
see it used for structural or high-strength parts, but you will see it a lot in sculpture
and decorative work. When exposed to air for long periods of time, it will get a
light-green coating, or patina, as on the Statue of Liberty.