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Other
systems use a lever type of tool to give the tooth form and
set. The set thickens and widens the blade section at the cutting
edge and causes a chip to be removed as the work is advanced
through the saw carriage. This increased width of the tooth
profile is necessary to reduce friction. As wood is compressed
by the cutting action, it expands again after the tooth has
passed. The reduced space may be insufficient for free passage
of the blade, causing it to bind.
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Lever
action. |
The
clearance provided by the widened tooth is referred to as the
kerf; some log rules for grading and cutting are based on a
1/4" kerf standard. Swaging also sometimes eliminated the
tedious filing of a tooth profile and those inconsistencies
found when filing and lever setting was used as the sharpening
method.
One advantage of a swage was its smaller size and the ability
to rework a blade without removing it from the mandrel. By 1900,
the replaceable point or tooth started to eliminate the extensive
handwork previously used on circular blades. These smaller points,
or bits, were consistent in size and could be quickly inserted
and the blade returned to service with minimal downtime. Band
mill blades continue to be sharpened in the same manner, although
the method is almost entirely by machine. For smaller woodlot
operations, the swaging process remained popular and, in some
cases, is still used today.
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Patent
application stamp. |
Jasper
Clark, of La Porte borough, Sullivan County, State of Pennsylvania,
sought to improve the methods already in place with his new
saw-tooth swage, under patent 226,977 of April 27, 1880.
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