Page 124 - Robot Builder's Bonanza

MAKING PLASTIC BASES 93

Figure 9-4 Use a hacksaw with a
medium- or fine- tooth blade to cut plastic.
For cuts with curves use a coping saw.

How to Drill Plastic

Wood drill bits can be used with expanded PVC and ABS, but for acrylic and polycarbonate
plastic the best bet is to use a drill bit that’s specially made for the job. What happens with
regular bits is that the flutes may suddenly get caught in the plastic, causing the tool to grab
the plastic and crack or break it.
Needless to say, not only does this wreck the piece, it’s dangerous, as tiny bits of plastic
fragments may fly through the air. That’s why you should always wear eye protection, even
when doing something as simple as drilling a hole.

START WITH A PILOT HOLE
If you can’t afford a specialty bit made for drilling in plastic, try starting the hole with a small
bit, say 5/64″, then gradually increasing the bit size until you get the hole you want. This
minimizes the “dogging” that can occur when the flutes of the bit get caught in the plastic. You
can use an ordinary high- speed steel bit when drilling into PVC.

RIGHT SPEED WITH POWER TOOLS
When making holes in plastic with a power tool, the drill should have a variable- speed control.
Reduce the speed of the drill to about 500 to 1000 RPM. When drilling acrylic and polycar-
bonate, always back the plastic with a wooden block. Without the block, the plastic is almost
guaranteed to crack. As with cutting, don’t force the hole and always use sharp bits. Too much
friction causes the plastic to melt.
Expanded PVC doesn’t usually require backing with wood, but be sure not to force the drill
bit through.

For more about drill tools and drilling in general be sure to read Chapter 6, “Mechanical
FYI Construction Techniques.”

Making Plastic Bases

I don’t hide that my unabashed favoritism in building robots is for plastic. For its size, plastic
is stronger than most woods, and it’s easier to work and cheaper than metal. My preferred

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