12.1 METAL-CUTTING SAWS
The first step in most machining jobs is to cut the
stock to required length. This can be done using
power saws, Figure 12-1.
There are three principal types of metal-cutting
saws, Figure 12-2. Reciprocating power saws use a
back-and-forth (reciprocating) cutting action. The
cutting is done on the backstroke. The blade is sim-
ilar to that found on a hand hacksaw, only larger
and heavier. Band-type power saws have a continu-
ous blade that moves in one direction. Circular-type
power saws have a round, flat blade that rotates into
the work. A toothed blade, friction blade, or abra-
sive blade may be used, depending on the material
and the operation.
12.2 RECIPROCATING POWER
HACKSAW
A reciprocating power hacksaw, Figure 12-3,
uses a blade that moves back and forth across the
work. The blade cuts on the backstroke. There are
several types of feeds available.
Positive feed produces an exact depth of cut on
each stroke. The pressure on the blade varies with
the number of teeth in contact with the work.
Definite pressure feed yields a pressure on the
blade that is uniform regardless of the number of
teeth in contact with the work. The depth of the cut
varies with the number of teeth contacting the work.
This condition prevails with gravity feed.
Feed can be adjusted to meet varying condi-
tions. For best performance, the blade and feed
must be selected to permit high-speed cutting and
heavy feed pressure with minimum blade bending
and breakage.
Standard reciprocating metal cutting saws are
available in sizes from 6″ 6″ (150 mm 150 mm)
to 24″ 24″ (900 mm 900 mm). The saws can be
fitted with many accessories, including quick-acting
vises, power stock feed, power clamping of work,
and automatic cycling of the cutting operation. The
latter moves the work out the required distance,
clamps it, and makes the cut automatically. The
cycle is repeated upon completion of the cut.
191
Chapter
12
Sawing and Cutoff
Machines
LEARNING OBJECTIVES
After studying this chapter, you will be able to:
Identify the various types of sawing and
cutoff machines.
Select the correct machine for the job to be
done.
Mount a blade and prepare the machine
for use.
Position the work for the most efficient
cutting.
Safely operate sawing and cutoff machines.
IMPORTANT TERMS
all-hard blade
cold circular saw
dry abrasive cutting
flexible-back blades
friction saw
gravity feed
horizontal band saw
raker set
three-tooth rule
wet abrasive cutting
Figure 12-1. The first step in most machining jobs is to cut the
stock to the desired length. Measure the cutoff length carefully
and observe all safety precautions. (DoALL Co.)