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116 WORKING WITH METAL

Improvement Store.” These pieces are meant to be used for such things as trim for a shower
door in the bathroom, but it won’t mind if it’s used for making a robot.
• U- channel (equal and unequal). U- channel is available with equal and unequal dimensions.
Pick the style best suited for your project. It’s available in thicknesses starting at 1/32″.
• Angle (equal and unequal). Available with equal and unequal sides, frames can be con-
structed using standard bracket hardware, pop rivets, and machine screw fasteners. Thick-
nesses start at 1/32″.
• Flat bar. Available in different widths and thicknesses, use this stock to make your own
brackets and support columns. It’s also useful as a reinforcement strap.
• Tubing. Available in square, rectangle, or round shapes. These tend to be the most expen-
sive, and are harder to build frames from.

Sources for these structural shapes include:

Larger dimensions: Your nearby hardware and home improvement store is likely to have
a good selection. Online is another choice if your local store is out of stock.
Smaller dimensions: Hobby and craft stores are your best bet. Some hardware and home
improvement stores also carry a limited assortment of the smaller pieces. As noted
earlier in the chapter, a popular maker of metal structural components is K&S Engi-
neering. Check their Web site at www.ksmetals.com for a description of their products.

Using a Backsaw and Miter Box
The process of cutting a frame from aluminum (or other) stock is the same as it is when mak-
ing a frame out of wood. So instead of repeating those steps here, please refer to Chapter 7,
“Working with Wood,” for the lowdown details.
A small, lightweight but sturdy frame can be constructed using 1/2″ 1/2″ 1/16″
U- channel stock, cut to length with miters. The 1/2″ dimensions are for the outside of the
stock; inside it’s 3/8″, so you can connect the pieces using
3/8″-wide L angle brackets (see Figure 11-7), also available
at your hardware store.
To assemble, use 4-40 machine screws and nuts. The
screws can be 3/8″ or 1/2″ in length. You need only one
screw per “leg” of the angle bracket— this makes it easier for
you to assemble the frame and saves on weight. In a pinch,
you can use 6-32 machine screws and nuts, but these are
bigger and heavier.

Creating a Box Frame
Box frames are three- dimensional bodies for your robots.
They can be constructed using two (or more) square frames,
anchored together with metal or plastic “pillars,” as shown
in Figure 11-8.
For good strength but less weight, I like to use 6mm PVC
for the pillars. These are cut to about 3″ wide. Then,
Figure 11-7 Solid metal frames can be
constructed out of U- shaped aluminum
channel, 3/8″ wide L angle brackets, and 1. Drill a pair of holes near both the top and the bottom of
metal fasteners. Cut the aluminum channel the pillar. Space the holes no closer than 1/4″ from the
with a miter box and hacksaw. top (and bottom), and no closer than 1/2″ from the sides.

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