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RAPID CONSTRUCTION WITH SEMIPERMANENT FASTENERS 147

the thickness or gluing on reinforcement strips out of thin wood or metal from the hobby
store.
CUTTING WITH A KNIFE

When cutting substrate with a knife, always use a sharp blade. Dull tools make you press down
too hard, which ruins the cut and increases the possibility that the knife will slip and cause you
injury.
Use a metal straightedge that you can hold down with one hand. I made mine out of
2″-wide aluminum I purchased at a hardware store for $5. Put a plastic handle in the middle.
(Be sure to countersink the holes on the bottom, and use flat- headed screws.) You can also
glue on a block of wood or plastic as the handle. You don’t need anything fancy.
To cut:
1. Use a #2 pencil to draw the line you wish to cut, even if you’re using a straightedge.
The line helps you know you’re cutting in the right spot.
2. Place the substrate material on a flat surface, covered with some kind of “sacrificial”
backing board— a piece of discarded paperboard or cardboard will do. You’ll cut into
this back instead of into the table.
3. Position the straightedge just to the side of the line, and hold down firmly.
4. Make an initial score (shallow) cut with the knife. Press the knife down just enough to
break through the surface of the substrate.
5. Repeat again for a thorough cut with the hobby knife. For deep cuts (1/8″ or more),
draw the knife over the substrate several times, being sure to retrace the same route
each time.
USING A MAT CUTTER

A mat cutter, designed for cutting out picture frame mats, also works well with softer sub-
strates like foamboard. Most mat cutters are designed with a built- in straightedge. The cutting
tool is enclosed in a heavy- duty handle, which slides along the length of the straightedge.
The advantages of mat cutters are that they’re generally safer to use than hobby knives
(though they can still cause injury if misused) and they’re more accurate. Be sure to use a mat
cutter with which you can adjust the depth of the cut— at least equal to the thickness of the
substrate material you’re using. Many penetrate up to 1/4″.
Not all mat cutters cut straight lines. Some are designed for curves and even circles. A circle
G cutter lets you make small, round bases— up to about 20″ diameter in some. Adjust the cutter to
a smaller size and you can even pop out your own wheels! If you don’t want to buy your own
circle cutter, see if your neighborhood picture framing store will make the cuts for you.

Rapid Construction with Semipermanent

Fasteners

Tape, ties, hold- downs, cable clamps, and hook- and- loop are used to produce semipermanent
rapid prototypes. The level of permanence depends on the product, the surface area (larger
tape = higher bond), and the material of your robot.

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