Improvements in the Manufacture of Implements and Tools having Cutting Edges.
Year: 1888

page_text: Date of Application, 9th Oct., 1888
Specification Accepted, 30th Nov., 1888
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Implements and Tools having
Cutting Edges. :
We, JOSEPHUS HOOPER, dentist, residing at 644 Fourth Avenue, in the city of
Louisville, County of Jefferson, State of Kentucky, and THOMAS CLARK, blacksmith,
residing at corner of 16th Street, and Dewey Street, in the city of New Albany, in
the county of Floy, State of Indiana, United States of America, do hereby declare
the nature of this invention and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :—
Our invention relates particularly to the manufacture of edged or cutting tools
having cutting faces of steel of appropriate temper, from ordinary hard castings
poured either from the blast furnace direct, or from a cupola or other furnace
wherein pig-iron is re-melted..
In the practice of our invention, we first produce a cast-iron blank of a shape
approximating that of the article when finished, but of considerable and uniform
thickness at that portion which is subsequently to form the steel cutting edges or
edges. Thus in casting a hoc-blade or a hatchet blank in this preliminary step of
our process, we have found it advantageous to have its outer edge of a uniform
thickness of from three sixteenths to one quarter of an inch.
The hard casting or blank is then packed in iron scale, hematite ore, or other
oxidizing agent, (as in the ordinary annealing process for converting cast iron into
malleable iron) and inserted in an annealing oven, where it is subjected to the usual
temperature incident to the process of annealing.
The annealing process thus begun, is however, interrupted at about two-thirds of
the ordinary period which would be required to convert the article treated into
malleable iron, (which period of course will differ according to the character of the
cast-iron composing it) and the casting is removed. The casting will then be found
to be partially decarbonized and in a uniform manner along its outer edges, which
retain from one and a half to two per cent. of carbon.
These edges however have still the coarse grain or structure of the original cast-
iron, and are therefore unsuitable to be sharpened and tempered at once.

page_text: We therefore, after removing the blanks from the annealing ovens, heat them to a
cherry-red heat and condense the grain at the edges by the blows of a hammer, at the
same time working the blank out into the shape of the finished article by bringing
the edges to the cutting point, the final cutting edge being formed if need be by
grinding.
The Blanks are thereupon re-heated to the required temperature depending upon
the thickness of the cutting edge and the amount of carbon retained and the edges
are tempered by being immersed in the heated condition in water, oil, or other
tempering liquid, thereby effecting the desired molecular change and distribution of
the carbon essential to a cutting edge.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what
we claim is :-
The method of making implements and tools with steel cutting edges from cast-iron'
which consists in first casting a blank or hard casting of a form approximating that
of the finished article, but of greater and uniform thickness at that portion intended
for the cutting edges; then partially decarbonizing said blank; thien working the
partially decarbonized blank at its cutting-edges until it assumes the shape of the
finished article, at the same time condensing the grain at said edges; and finally
tempering said edges; substantially as described.
Dated this 9th day of October 1888