Improvements in Apparatus for Grinding and Gauging Twist Drills.
Year: 1892

page_text: Date of Application, 25th Apr., 1892
Complete Specification Left, 25th Jan., 1893-Accepted, 25th Apr., 1893
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Grinding and Gauging Twist Drills.
ROBERT ABRAM LEE 76, High Holborn London W.C. Consulting Engineer
do hereby declare the nature of this invention to be as follows:-
My invention consists of a rest or socket, and a stem fitting it, and fixed in
position by a set screw. The upper part of this stem has attached to it a tube or
holder, placed at an angle equivalent to the clearance of the cutting face of a
twist drill. To this stem is fixed a gauge in such position that it's edge is parallel
to the face of a grindstone, or emery wheel (when the rest is clamped on to the
machine which carries the grinding wheel) and the cutting edge of the drill is at
the correct angle for grinding. This gauge is for setting the apparatus; which can
be attached to any grinding machine, or lathe.
Attached to, and preferably in the front part of the holder, is a stop piece which
goes into one of the flutes of the drill, and is placed in such position that it only
allows the drill to be rotated a sufficient distance to bring one surface of the drill
against the grinder. The drill is fed forward, and rotated by a winged collar, held
on it by a set screw, and operated by hand, this collar is placed on the drill in such
position, that when the collar comes against the end of the holder, the first lip is
properly ground.
All that is necessary to complete the grinding is to draw the drill back until the
flute is clear of the stop, give the drill half a revolution and push it forward in
the holder repeating the grinding operation until the collar again comes in contact
with the socket, when the drill will be correctly and truly ground. It is obvious
that the holder may be either a tube, V block, or a bar with collars on it, and the
stop piece for deciding the amount of rotation of the drill. The foregoing
description applies to a holder with a fixed backing off angle, but when it is
required to vary this angle, I make the holder loose from the stem, and the stem to
terminate in an angular socket set off from it. The holder is provided with stem
to fit this socket, allowing it to be fixed at various clearance angles to the face of
the grinder, a set screw being provided to fix the holder in position.
A graduated scale can be attached so that the holder can be shifted and replaced.
I also make a separate gauge for the drill points, by drilling a hole to a depth of
about two diameters of the drill, and I cut away-at the bottom end of the hole→
the metal, longitudinally, and half way through the diameter, the front end of this
cut part, being at the same angle as the backing off of the drill. By placing a
drill in this gauge it can be at once seen whether the lips are equal, of the correct
angle, and properly backed off.
The grinding holder before described, is made to suit various diameters of drills
by a series of bushing pieces; fitting one into the other, each having a slot for the
stop piece to fit into, and being provided with a corresponding stop on the opposite
side.
Dated this 23rd day of Anril 1892.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Grinding and Gauging Twist Drills.
ROBERT ABRAM LEE, 203 Shaftesbury Avenue London W.C. (late of
76 High Holborn London W.C.) Engineer, 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 :-
My invention consists of a rest or socket and a stem fitting it. The upper part &
of this stem has attached to it a tube or holder, placed at an angle equivalent to
the cutting face of a twist drill.
· The apparatus can be attached to any grinding machine or lathe.
Attached to and preferably in the front part of the holder, is a stop piece the
end of which goes into one of the flutes of the drill. The drill is fed forward and 1
rotated by a winged collar held on to it by a set screw, and operated by hand, and
this collar is placed on the drill in such position that when the collar comes against
the end of the holder the first lip is properly ground. All that is necessary to
complete the grinding is to draw the drill back until the flute is clear of the stop,
give the drill half a revolution & push it forward in the holder repeating the 1
grinding operation until the collar again comes in contact with the socket, when
the drill will be correctly & truly ground.
.
It is obvious that the holder may be either a tube, V block, or a bar with collars
on it, and the stop piece for deciding the rotation of the drill.
I also make a separate gauge for the drill point, by drilling a hole, about equal a
in depth to two diameters of the drill, and I cut away-at the bottom end of the
hole the metal longitudinally and half way thro' the diameter, the front end of
this cut part being at the same angle as the backing off of the drill. By placing
a drill in this gauge it can be at once seen whether the lips are equal, of the
correct angle, & properly backed off.
The grinding holder before described is made to suit various diameters of drills
by a series of bushings pieces fitting one into the other, each having a slot for the
stop piece to fit into and provided with a corresponding stop on the opposite side.
I hinge the stop piece so that it can he moved away, if desired, after the drill is
set in position.
In order to produce the, so called, chisel point on the drill and to more evenly
wear the stone or emery wheel, I fit the holder with a spiral arrangement to cause
the drill to advance toward the stone and a cam arrangement which comes in
contact with a projecting lug fixed to the socket, the drill in this case is secured to
& rotated by the cam and as it rotates, owing to the forward movement caused by
the spiral, and the outward sweep of the tail end of the drill, caused by the cam,
acting together; the effect produced is to leave a perfect chisel point to the drill
together with the correct angle for the cutting edges. The cam has attached to it
a pin to fit into the slots of the bushings, and the amount of revolution of the drill
is determined by the cam.
Referring to the accompanying drawings
Fig. 1 is an elevation partly in section Fig. 2 a plan of the apparatus.
The lines A. A. B. B. represent the face of the stone or emery wheel. C is the
rest socket. D the holder. E the drill, in bushing F. This bushing has a collar
on it at and its front end is screwed to fit the nut. H. G is the fixing collar, with
a set screw to fix it on to the drill, this collar bears against the adjustable nut H,
and this nut screws on to the bushing F, by turning the nut H it presses the
collar and advances the drill toward the stone. A set screw is provided at 1
to fix the drill in the bushing. I is the stop piece engaging with one of the lips
of the drill and hinged at this is used to set the drill diametrically and it is
moved out of the drili while this is being ground. J is the projecting lug &
K the cam acting against this lug, in the cam K is a pin K 1, and this pin passes

page_text: through the spiral groove K 2 in the holder D and its lower end fits into a hole in
the bushing this pin K 1 connects the cam and the bushing F together, so that
when the cam is revolved by the lever K3 the pin K 1 revolves the bushing F and
the drill with it, as this pin travels through the groove K2 it also moves the
bushing F forward, the cam K at the same time pressing against the lug J, causes
the outward sweep of the tail end of the drill.
Fig. 3, N is a front view of the drill gauge showing a drill in position for gauging,
& Fig. 4, O is a side view of the gauge.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1st. In a twist drill grinder. The holder D, and the bushings F, and the adjustable
collar H, substantially as described.
2nd. The spiral movement and the cam movement, for producing the correct
curve, and the chisel point to a twist drill substantially as described.
3rd. The gauge for gauging the cutting end of twist drills substantially as shown
and described.
4th. The general combination substantially as shown & set forth, forming my
improved apparatus for grinding and gauging twist drills.
Dated this 25th day of January 1893.
DANEDA ADDAMTWT
ROBERT
חד ADA T