Chapter 8 Power Tools 187
Copyright Goodheart-Willcox Co., Inc.
Types of Drill Bits
Auger
Designed for boring relatively large holes in soft
materials. Threaded tip helps to draw bit into the
work without a pilot hole. May have single, double,
or triple flutes.
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High-Speed Steel (HSS) Twist
Multipurpose bit used on wood, metals, and plastic
materials. Always use a center punch to initially guide
the bit, and drill pilot holes for larger bits.
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Spade or Paddle
Commonly used for boring holes in lumber. Relies
on operator pressure to penetrate the wood. Versions
with threaded points aggressively pull themselves into
the work.
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Masonry
Designed with a hardened, chisel-like tip that is used
to chip through hard, brittle materials such as stone,
tile, and concrete. Some are heavily reinforced and/or
equipped with SDS shanks for use in hammer drills.
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Forstner
Complex bits capable of boring nearly flat bottomed
holes of often large diameter. Used frequently by fine
carpenters and furniture makers. Best suited for use
in drill press to maintain stability.
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(Continued)
Figure 8-9. Common types of drill bits.