AN IMPROVED PROCESS OF SHARPENING FILES
Year: 1879

page_text: LETTERS PATENT to Alexander Melville Clark, of Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "AN IMPROVED
PROCESS OF SHARPENING FILES." A communication from abroad by David
Wilder Watson, of Malden, in the County of Middlesex, State of Massachusetts,
United States of America.
Sealed the 1st August 1879, and dated the 24th February 1879.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 24th February 1879.
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middlesex,
Patent Agent. "AN IMPROVED PROCESS OF SHARPENING FILES." [A commu-
nication from abroad by David Wilder Watson, of Malden, in the County of
Middlesex, State of Massachusetts, United States of America.]
The object of this Invention is to sharpen or recut worn out files in a simple,
cheap, and expeditious manner. It consists in subjecting the file to the action of
nitric acid placed in the scores or depressed lines of the file, where it eats the sides
of the burrs, thus sharpening their edges and deepening the scores or depressed lines
between the same.
I proceed as follows in applying the process:-I pour the nitric acid upon the
file and it fills into the scores or depressed lines, where it is allowed to stay eating
into the metal until its strength becomes exhausted. I then wash the file
thoroughly in clean water and apply more acid the same as before, and continue to
do so until the burrs reach the necessary sharpness of edge. In this way it will be
found that the worn out files can be more quickly and efficiently recut than by any
hand method now employed. The steel retains its original quality without any deterio-
ration whatever, a condition that cannot be retained after the file has been recut by
hand. Moreover the process is quite inexpensive; and, lastly, the recutting can be
done a number of times, depending upon the thickness of the files and other
conditions.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
11th August 1879.
ALEXANDER MELVILLE CLARK, of Chancery Lane, in the County of Middlesex,
Patent Agent. "AN IMPROVED PROCESS OF SHARPENING FILES." A commu-
nication from abroad by David Wilder Watson, of Malden, in the County of
⚫ Middlesex, State of Massachusetts, United States of America.
The object of this Invention is to sharpen or recut worn out files in a simple,
cheap, aud expeditious manner. It consists in subjecting the file to the action of
nitric acid placed in the scores or depressed lines of the file, where it eats the sides
of the burrs, thus sharpening their edges and deepening the scores or depressed
lines between the same. I proceed as follows in applying the process :-I pour the
nitric acid upon the file and it fills in the scores or depressed lines, where it is
allowed to stay, eating into the metal until its strength becomes exhausted. I then
wash the file thoroughly in clean water and apply more acid the same as before,
and continue to do so until the burrs reach the necessary sharpness of edge.
In this way it will be found that the worn out files can be more quickly and
efficiently recut than by any hand method now employed. The steel retains its
original quality without any deterioration whatever, a condition that cannot be
retained after the file has been recut by hand. Moreover the process is quite
inexpensive, and the recutting can be done a number of times, depending upon the
thickness of the files and other conditions.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
hereinbefore in part recited Letters Patent is,—
1. As an improvement in sharpening or recutting files, the process herein
described, consisting in subjecting the scores or depressed lines of the file and the
sides of the burrs to the action of nitric acid, in the manner and for the purpose
substantially as described.
2. As an improvement in sharpening or recutting files, the process hereinbefore
described, consisting in pouring nitric acid on the file so that it will fill the scores
or depressed lines, and allowing it to remain there to eat away the sides of the
burrs and deepen the lines until it is exhausted; then washing the file clean in
water, and applying more acid as before, until the required sharpness of the burrs
is obtained, substantially as described.
In witness wheroof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Eleventh day of August, in the year of our Lord
One thousand eight hundred and seventy nine.