Chapter 8 Power Tools 181
Copyright Goodheart-Willcox Co., Inc.
It once was commonplace to have all of the stationary power tools in a shop
linked by a series of overhead drive belts and pulleys, all driven by a single
power source. This is similar to today’s farm practice of relying on a single
tractor outfi tted with a variety of agricultural equipment to perform many
different functions.
Stationary Electric Power Tools
The development of increasingly more effi cient electric motors led to the
constant improvement of electrically powered tools. Stationary power tools
are constructed with relatively heavy bases intended to stabilize the machine
during operation. Most include mounting systems to be secured to the fl oor
or workbench tops.
Today, most stationary tools are powered by a dedicated electric motor.
These machines use the same standard alternating current (AC) electric
power that is used in most American homes. Agricultural applications
commonly use 120-volt or 240-volt power. However, larger industrial
machines may require the use of higher voltages.
Stationary electric equipment may be connected to the power source
by a wall plug or by hard wiring. Hard wiring is directly connecting the
electric wiring of a tool to the wiring of the electric supply system—no
wall plug is necessary. Power tools that are usually operated in stationary
positions but are occasionally moved require plugging a power cord into a
wall receptacle.
Portable Electric Power Tools
Portable power tools are traditionally powered through an electric
power cord plugged into standard 120-volt AC current. Larger tools may
require 240-volt AC current. Portable grinders, drills, and saws may also
be powered by direct current (DC) power sources. Many portable welding
machines have convenience outlets connected to the same DC generator
that produces the welding current. Some portable electric power tools are
confi gured to use either AC or DC current; these are machines intended for
use in fi eld applications.
Safety Note
Extension cords are used as temporary wiring additions to the permanent electrical
system of a building. Although not ideal, extension cord use is inevitable on many job
sites. Grounded three-conductor extension cords made of strong, durable material
should be used for powering portable tools and equipment. A few safety rules will help
you prevent tool and cord damage and avoid injury:
• When choosing the proper extension cord to use on a job, check that the cord’s
amperage rating is high enough to handle the amperage of the power tools or
equipment that will be connected to it.
• Never use a frayed or damaged extension cord.
• Always be mindful of the location of extension and power cords when using portable
power tools.