The teeth of an "increment-cut"
file are irregularly spaced, the method followed by a prominent
concern being as follows: The rows of teeth are spaced
progressively wider from the point towards the middle of the
file, by regular increments of spacing, and progressively
narrower from the middle towards the heel, by regular decrements
This spacing of the teeth is
modified by introducing, while the teeth are being cut, a
controllable irregularity as to the spacing, which is confined
within maximum and minimum limits but is not a regular
progressive increment or decrement.
The successive rows are not exactly
parallel, but are cut slightly angular with respect to each
other, the angle or inclination being reversed during the
operation of cutting, as may be required. It will be
understood that the increments of spacing are very small.
The theory is that if the teeth are
equally spaced and have a uniform height and outline, the file
will not cut so readily, the reason being that when so many
teeth are in contact, considerable pressure is required to make
them cut; but when the teeth are slightly irregular in height, a
smaller number will be in contact and the pressure required will
be correspondingly light. As the longer teeth wear down,
the shorter ones will begin to work, although then the file will
not cut so freely.
File teeth are also formed by the
increment-cut, so that they will produce smoother surfaces.
If the teeth follow each other at regular intervals, they tend
to drop into the cuts or furrows made by the preceding ones,
causing chattering; the uneven teeth of hand and increment-cut
files tend to prevent this chattering. The opinions of
file makers differ regarding the foregoing advantages and
Cyclopedia of Applied Mechanics, 1888
This name is given to a machine-cut
file manufactured by the Nicholson File Company, the rows of
teeth of which are spaced progressively wider, from the point
toward the middle of the file, by regular increments of spacing;
and progressively narrower, from the middle toward the heel, by
regular decrements of spacing.
This general law of the spacing of
the teeth is modified by introducing, as they are cut, an
element of controllable irregularity as to their spacing; which
irregularity is confined within maximum and minimum limits, but
is not a regular progressive increment or decrement.
The teeth are arranged so that the
successive rows shall not be exactly parallel, but cut slightly
angularly with respect to each other, the angle of inclination
being reversed during the operation of cutting, as necessity
Files possessing the
characteristics above mentioned do not produce channels or
furrows in the work, but effect a shearing rut, for the reason
that no two successive teeth in any longitudinal row of a
cross-cut file are in alignment; the file is, it is claimed,
thereby able to cut more smoothly and more rapidly, and
possesses greater endurance as a tool for dressing metal than
files not so cut.