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Breaking In Blades
Proper break-in is important for the cutting
performance and longevity of the blade. During
the break-in period, only mild pressure should
be exerted on the blade (about half of the normal
feed pressure for a properly broken-in blade). The
duration of the break-in period is determined by
the hardness of the material cut. The break-in
period is defined in terms of square inches of
material cut.
•
For hard materials, such as steel, the break-
in period is the first 50 square inches of
material cut.
•
For soft materials, such as aluminum, the
break-in period is the first 150 square inches
of material cut.
To determine the square inches of a cut, calcu-
late the area of the cross-section of the work-
piece. Keep in mind when cutting hollow-section
pieces that the area only includes the solid walls
of the workpiece. Refer to Figure 29 to calculate
approximate square inches for many typical cuts.
A = L x H
H
L
)² x π
D
A = (
⁄
2
D
D x π x Th
Th
A
Th
A
2H + 2L x Th
H
L
Figure 29. Calculating cut area for break-in.
Model T28366 (Mfd. Since 04/18)
A =Area
H =Height
L =Length
D =Diameter
Th =Material
Thickness
π =3.14
Controlling Feed
Rate
Blade feed rate refers to the period of time it takes
to cut through a workpiece. Feed rate is controlled
by the amount of pressure exerted on the handle
by the user. Pulling hard on the lever will result in
a greater feed rate, whereas only pulling lightly will
result in a very slow feed rate.
Cutting with a feed rate that is too slow can result
in lengthy, inefficient cuts and in some cases,
tooth dulling or overheating. The chips produced
by the cut will generally be thin or powdery.
Cutting with a feed rate that is too fast may cause
the blade to wander, resulting in cuts that are not
straight, and will generate excess heat and dull
the blade. The chips produced by the cut will
generally be thick and hard. When cutting small or
thin-walled workpieces, the edges of the cut may
become rough or torn.
Feed rate will vary depending upon the type of
material being cut, the proper flow of coolant,
and the amount of pressure applied by the user.
Practice on a sample workpiece to learn how
much pressure is needed for a specific cut.
-23-
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