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Increment-cut Files by Machinery's Handbook, 1914

 

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 of spacing.

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 objections.

Increment-Cut File from Appletons' 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 requires. 

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.

WK
09/2012


 
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