188 Agricultural Mechanics and Technology Systems
Copyright Goodheart-Willcox Co., Inc.
Drill Bit Materials
Material used to manufacture drill bits must be harder and stronger than
the work material. Bits designed for drilling steel have to be signifi cantly
harder than bits designed for boring holes in wood.
High-speed steel (HSS) is the material most commonly used to make drill
bits. HSS bits are good for drilling wood, most plastics, aluminum, and soft
steels. Cobalt bits include 5%–8% of cobalt blended into the steel. This creates
a more durable bit that is suffi ciently hard for drilling into hard materials
such as stainless steel. Carbide bits are the hardest bits readily available, but
they are also the most brittle and require extremely stable drilling conditions.
Types of Drill Bits
(Continued)
Step Drill
Designed with multiple bit sizes on the same self-
piloting bit. Limited to use on thin materials. The
diameter of the hole is determined by the depth to
which the bit is allowed to penetrate.
Eimantas Buzas/Shutterstock.com
Countersink
Used to shape the top of the hole to fit the fastener
when screws designed to fit flush with the surface of
the work are used. May employ a short piloting point or
the entire length of the pilot bit.
Goodheart-Willcox Publisher
Christopher Elwell/Shutterstock.com
Tile and Glass
Uses hardened tips that may be imbedded with
abrasive materials to cut glass and ceramic tile.
Lubricating and cooling the bit with a water bath during
drilling is often recommended.
Goodheart-Willcox Publisher
Coprid/Shutterstock.com
Hole Saw
A saw blade formed in a circle for cutting large holes.
Available for cutting a variety of materials. Incorporates
a pilot bit that keeps the saw aligned.
Dan Kosmayer/Shutterstock.com