IMPROVEMENTS IN MACHINES FOR SHARPENING TWIST DRILLS
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the
Office of the Commissioners of Patents, with his Petition, on the
5th January 1875.-A communication from abroad by Claus
Van Haagen, of Philadelphia, Pennsylvania, United States of
America.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN MACHINES FOR SHARPENING TWIST DRILLS," a
communication to me from abroad by Claus Van Haagen, of Philadephia,
Pennsylvania, United States of America, to be as follows:---
This Invention has for its object imparting an accurate cutting edge
to a twist, bit, or drill, and consists of a peculiar arrangement of
mechanism, whereby that operation is greatly facilitated.
In the operation of sharpening the twist drill if the drill be simply rotated
while its cutting end is applied to the stone, the result will be inefficient
cutting edges, the absence of the requisite chisel point, and the reduced.
portions will be at the same angle throughout in respect to the longi-
tudinal central line of the drill, whereas each of the said portions should
present an angle gradually diminishing or becoming more acute from the

page_text: conformation of the end of the drill may be obtained by simply moving
the said drill radially while the end of the drill is applied to the stone,
and while it is turned on its own axis, a slight forward movement being
at the same time imparted to the drill.
In carrying out this Invention a machine is constructed, based on these
required movements of the drill, while it is applied to the stone and
arranged in the following manner:-On the bed plate of the machine
there are fitted two carriages, one carrying the grindstone, and the other
the bit, the centre lines of both of which should be on the same horizontal
plane. The grindstone shaft turns in suitable bearings on its carriage
or headstock, and the latter slides on inclined guides on the bed plate,
on which it may be moved to and fro by a lever and connecting rod or
equivalent appliances. The carriage carrying the bit is pivoted to the
bed plate by a bolt, the central line of which should be on a vertical line
parallel with the grindstone shaft, and tangential to the periphery of the
stone, and in order that these relative positions may be preserved the
said bolt is rendered adjustable in a slot in the bed plate at right angles
to the shaft, and the carriage has a slot at right angles to the other slot
which permits it to be adjusted on the bolt. The bit is fitted into a
tapering socket in a hollow shaft which is supported by an adjustable
headstock and fixed standard on its carriage, the said shaft admitting of
being turned independently of a sleeve in the headstock to the extent
permitted by a spiral slot into which a pin on the shaft projects, or the
slot may be in the shaft and the pin on the sleeve. The shaft admits
also of being moved longitudinally through without turning inde-
pendently of a sleeve in the standard before mentioned. A ring
adapted to a recess in the adjustable headstock encircles the sleovo
firstly mentioned, and is provided with a set screw by which it may be
firmly secured to the said sleeve, thus preventing all longitudinal
movement of the latter, but permitting it to be turned with the said
ring to the extent of exactly one half a revolution in either direction,
which is determined by a spring stud of the headstock adapted to either
of two recesses at opposite points of the ring. Simple stops on the head-
stock and a projection or projections on the ring may however be
substituted for the above mentioned spring stud and recesses, as a means
of determining the extent of the movement of the said ring. The sleeve
in the fixed standard has a free rotary movement in such standard, but