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Technical Guide: Blade
Basics
BLADE TERMINOLOGY
1. GAGE - The thickness of the blade.
2. BLADE WIDTH - The distance from the tip of the tooth to the
back edge of the blade.
3. SET - The bending of teeth right or left to allow clearance of
the back through the cut.
4. TOOTH BACK - The surface of the tooth opposite the tooth face.
5. TOOTH TIP - The cutting edge of the tooth.
6. TOOTH FACE - The surface of the tooth on which the chip is
formed.
7. TOOTH - The cutting portion of the saw blade.
8. TOOTH RAKE ANGLE - The angle of the tooth face measured to a
line perpendicular to the cutting direction of the saw.
9. T.P.I. - The number of teeth per inch.
10. GULLET - The curved area at the base of the tooth.
11. GULLET DEPTH - The distance from the tooth tip to the bottom
of the gullet.
12. BLADE BACK - The body of the blade not including the tooth
portion.
13. TOOTH PITCH - The distance from the tip of one tooth to the
tip of the next tooth.
CORRECT TOOTH
SELECTION
When the time comes to select the right number of teeth, try the
following rule of thumb:
3 - 6 - 9 -
20
You should have a minimum of 3 teeth in the work at all times;
having 6 to 9 teeth in the work is the optimum number; but more than
20 is too many teeth in the work.
There have been advances in blade design and manufacture, plus
some testing results which tell us the following:
A) When
cutting mild materials on a bandsaw you should use the 3 - 6 - 9 -
20 formula.
B) When cutting hard materials on a bandsaw, a few
more teeth in the work piece will produce better blade life. This
will not reduce the cutting time appreciably, but will increase
blade life.
C) When cutting tough materials (alloys containing
nickel and space-age materials), a positive tooth should be
used.
CONSTANT PITCH
The constant pitch tooth design is widely used for both cutoff
and contour work and may be used for ferrous and non-ferrous
materials. All constant pitch tooth configurations have a fixed
number of teeth per inch. Available in both raker or wavy set,
depending on tooth pitch selected.
SKIP TOOTH
The skip tooth design has greater
gullet capacity for better chip clearance on softer metals, woods,
plastics or compostiton materials. As the name implies, every other
tooth is removed or skipped, without weakening the overall
blade.
HOOK TOOTH
The hook tooth is similar to the
skip tooth except the tooth face has a 10° rake angle which "hooks"
or bites into the material more efficently, and penetrates the
material better, even at reduced feed pressures.
BROACH TOOTH
The broach
tooth was the original "varied pitch" developed by Diamond Saw
Works, Inc. as early as 1937. Its generating cutting action is
accomplished by varying the tooth pitch and set angles, giving
marked improvement in a blade's cutting speed and life, smoothness
of cut and greatly reduces noise and vibration in the cutting
application. An exceptional tooth design for the tougher cutting
jobs. Broach tooth blades have a special set.
POSI TOOTH
The posi tooth is
an improved variety of the broach tooth blade when a positive rake
angle is desired. The hook tooth design has been applied to the
proven principle of the broach tooth, giving additional value and
performance. All posi tooth blades have a special set.
PROPER SET SELECTION
RAKER SET
Widely used on all types of blades
and teeth. Its pattern is one tooth set left, one tooth set right
with the third tooth straight or unset. This pattern allows for
fast, efficient cutting and uniform saw kerf. Generally used on
solids and thicker sections.
WAVY SET
Groupings of teeth are alternately
set to the left and to the right, forming a wave pattern. Used for
cutting thin or interrupted sections where tooth breakage or
stripping is experienced. Because a group of teeth are set left,
then right, the strain on each individual tooth is reduced.
E.T.S. (EVERY TOOTH SET)
Each tooth is set
alternately left, then right. Used generally in woodworking or for
nonferrous metals. Also known as alternate set.
NOTE: Broach tooth and posi tooth blades are specially set to
suit each tooth design. Their sets do not necessarily conform to any
of the above descriptions. | 
