Page 143 - Robot Builder's Bonanza

112 WORKING WITH METAL

There’s lots of variety to choose from, allowing you to pick the extrusion to match your
project. Common shapes include equal and unequal L- angles, U- channels, and flat bars.
I’ve found the following extrusions among the most useful in my robot building. Try these
for starters, but don’t be afraid to select other shapes and sizes for your projects. For easy
comparison, several of the most popular extrusion variations are shown in Figure 11-3.
• U- channel— equal and unequal sizes. A popular size is 1/2″ 1/2″ 1/16″ U- channel,
which is sold as trim edge for 3/8″ plywood.
• Angle— equal and unequal. The 1/2″ 1/2″ 1/16″ (equal) angle stock is especially
useful for use in robots up to about 15″ in size.
• Bar and rod. Example: 3/4″-wide 1/16″-thick flat bar.

TIE PLATES
Tie plates are designed to strengthen the joint of two or more pieces of lumber that are nailed
together. The plates are made of steel but are galvanized to resist rust. The galvanizing gives
the metal a noticeable mottled look.
Check for this stuff in the lumber area of your home improvement store. Much of what
they’ll offer is preformed shaped for specific jobs, such as attaching 2- by- 4 lumber to a ceiling
beam. What you want is the flat plates (or flat plates with a flanged edge; those are useful,
too), available in several widths and lengths. Common widths are 3″ to 5″ and lengths from
3″ to 7″. See Figure 11-4 for a size comparison of popular 3″ 5″, 3″ 7″, and 3″ 9″
plates.
You can use the plates as is or cut them to size. The plates have numerous predrilled holes
to help you hammer in nails, but the metal is thin enough (usually 20 gauge or so) that you
can drill new holes. Just be sure to use sharp drill bits.
In North America the most common brand of tie plate is the Simpson Strong- Tie. Visit the
company’s Web site (www.strongtie.com) for sizes and specifications of their various prod-

5"

7"

3-1/8"

9"

Figure 11-4 Tie plates are made of galvanized
Figure 11-3 Look for extruded aluminum at your steel and are useful as base or construction metal for
neighborhood hardware or home improvement store. It your robots. They come in different sizes; avoid
comes in various lengths and may be cut to size using a unnecessary cutting by matching the size to best fit
hacksaw. your intended use.

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