Page 87 - Robot Builder's Bonanza

56 BUILDING ROBOT BODIES— THE BASICS

Drill bits under 1/4″ are also identified by their numerical size. For example, a #36 bit is the
FYI same as 7/64″. See Appendix C, “Mechanical Reference,” for a handy chart comparing
number drill bits with their fractional counterparts.

• The least expensive drill bits for robot building are made of high- carbon steel.
• Better drill bits are made with high- speed steel, and these keep their sharpness for longer.
These are fine for most amateur robotics workshops.
• Tungsten carbide bits stay sharp the longest even when cutting metal. They’re more
expensive than the others.
• Cobalt bits are the Terminator of the bunch. They drill into most anything, including hard-
ened steel.
Drill bits have different kinds of coatings, which extend their life. However, when coated,
the bit usually can’t be resharpened, as the resharpened edge will no longer have the coating.
Black oxide coating is the least expensive of them all, and is useful for wood, soft plastic, and
thin aluminum. Various titanium coatings greatly extend the life of your bits, allowing you to
use them on thicker aluminum and steel.

G Save money! Get a standard fractional drill set in standard high- speed steel, then augment that
set with specific sizes of more- expensive longer- lasting bits. The most commonly used bit in my
shop is 1/8″, so I get extras of those with a titanium coating.

SCREWDRIVER BITS
When you find you’re doing a lot of screw assembly, invest a few dollars in a set of Phillips
and flathead bits for use in drills and motorized driver tools. These fit into the drill chuck like
any other bit but are used to tighten and untighten screws. To be useful, your drill needs
a variable- speed motor; you’ll surely strip out the screws if you try to use the bits at high
speed.

HOBBY KNIFE
Hobby knives include the X- Acto brand, sporting interchangeable blades. They’re
ideal for cutting cardboard, foamboard, and thin plastics. A word of caution: The
blades in these knives are extremely sharp. Use with care.

NUT DRIVER
Nut drivers look like screwdrivers, but they’re made to tighten hex- head (six- sided)
nuts. They come in metric and imperial (inch) sizes. On the imperial front, common
driver sizes are:

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