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Almost all wood cutting saws require the teeth to be wider
than the body of the blade. This is referred to as set.
Without it, the blade will eventually bind, as the wood
fibers recompress against it. One method of creating set
is by bending all the saw's teeth slightly in an even,
controlled manner, with alternate teeth being bent in
opposite directions. This allows the saw blade to cut
without wandering, enabling the sawyer to maintain line
and cadence. Some manufacturers taper grind their blades
to further facilitate that clearance. However, set does
not guarantee that a saw will cut cleanly or with any
speed; the sharpness of the tooth and the particular rake
angle determine movement of a saw blade through material.
The early saw set shown here is the hammer type. To use
it, a saw blade is inserted between a shaped punch and
a fixed-angle anvil. The punch is struck, and the tooth
is offset. Clearance is maintained by the spring, which
moves the striker up and away after each hammer blow.
The saw blade is held in position with the moveable rest,
which allows for parallelism as the blade is moved across
the anvil.
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This saw set is conspicuously marked with, "J.
Boggs", "Patent", and the owner's initials
"MT" in a cartouche. A patent search indicates
that John Boggs of Philadelphia, Pennsylvania was issued a patent
for a saw set on October 4, 1827. On December 15, 1836,
a fire destroyed the United States Patent and Trademark
Office (U.S.P.T.O.). The first 10,000 (approximately)
American patents and models were lost in the fire. (Diligent
members of the office staff were able to save some.)
The search further shows that this patent was reissued
under the X-patents (refers to U.S. patents issued between
1790 and 1836, before the U.S.P.T.O. began numbering
patents) and given the number 4888x. No abstract or
claims paper is available for examination. Although
this saw set is clearly marked and closely resembles
the patent drawing, it is not an exact copy. This is
a common practice in the transition from invention to
commercial manufacture.
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