Chapter 8 Power Tools 205
Copyright Goodheart-Willcox Co., Inc.
Jig Saw Blades
Most jig saw blades are only 2″ to 3 1/2″ long.
This is adequate because the stroke of the blade is only
1/2″ to 1″ long. Blades are marketed according to the
material they are designed to cut. However, when
choosing which blade to use for a particular job, it is
helpful to consider several factors. Carbon-steel blades
are the most widely available and are adequate for soft
woods and plastics. Stepping up to high-speed steel
blades is necessary for cutting soft metals such as
aluminum or brass; also, HSS blades last nearly fi ve
times longer than carbon-steel blades. For ferrous
metals or hard abrasive materials, a bimetal blade
cuts more effi ciently and has a longer cutting life
than softer blades.
High TPI counts can cut harder materials and
produce smoother but slower cuts than rapid-cutting
blades with low TPI counts. The way the teeth of jig
saw blades are sharpened and set also affects their
cutting ability.
Teeth that are formed sharp in the initial blade-
making process (milled) are designed for quick but
rough cuts. Milled teeth usually outlast ground teeth
when used in similar materials. See Figure 8-36.
Ground teeth go through a secondary sharpening
process during blade making, which produces sharper teeth that are capable
of fast, smooth cuts in wood. Some blades combine ground teeth with a
tapered back to give a clean cut with a reduced kerf width.
Most jig saw blades are designed with the teeth cutting toward the base
of the saw on the pulling stroke. Blades designed to cut on the downward
stroke are used to cut some plywood and
laminates. This design ensures that the
cleanest side of the cut is on the top of the
material. Special blades with abrasives
bonded to the cutting edge are designed for
cutting materials such as concrete board,
glass, and tile.
Scroll Saws
Scroll saws use a reciprocating blade
action similar to reciprocating saws and
jig saws. The difference is that scroll saws
are stationary tools, and their blades
are secured at both ends, Figure 8-37.
Extremely intricate cuts—much fi ner than
possible with a band saw or jig saw—are
possible in wood, plastics, and soft metals.
A B C
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Figure 8-36. Most jig saw blades are designed to
cut on the pulling stroke like blades A and B. Blade
C cuts on the pushing stroke and is used for cutting
veneers used in cabinetmaking. Blades A and B
have milled teeth, while blade C has teeth that
were formed by grinding.
Blower
Base
Table
Guard
Upper
blade clamp
Blade control
Power switch Upper control arm
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Figure 8-37. A typical scroll saw can make delicate and intricate
cuts.