Improvements in Twist Drill Grinding Devices.
Year: 1892

page_text: Date of Application, 13th Dec., 1892-Accepted, 4th Feb., 1893
COMPLETE SPECIFICATION.
Improvements in Twist Drill Grinding Devices.
I, JOHN HEDVIK BERGSTROM of No. 562 Baltic Street, in the City of
Brooklyn, in the County of Kings and State of New York, United States of
America, Mechanical 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 in the improved twist drill holder and gauge for guiding
twist drills accurately and with suitable clearance of the point all as hereinafter
fully described reference being made to the accompanying drawings in which :-
Fig. 1, is a plan view of my improved holder.
Fig. 2, is an elevation partly in section on line, a, Fig. 1.
Fig. 3, is a side clevation as seen looking in the direction of the arrow at Fig. 1.
Fig. 4, is a horizontal section on line y, y, Figs. 2 and 3.
Fig. 5, is a diagram illustrating the mode of using the holder, and
Fig. 6, represents a key wrench in side and plan views for working the screw to
adjust the jaws that hold the drills.
In the first place I provide any approved centering chuck for holding the drills a,
as the head b, shank c, jaws d and screw e, said head and shank being connected by
the screw joint at a, and having the longitudinal bore y, for reception of the drill
shanks, the jaws being arranged to slide transversely in suitable ways in the head,
and the screw being arranged along one side of the jaws and geared with them
by right and left hand screw threads respectively, and fixed immovable lengthwise
but so as to be turned freely by a key wrench 1, inserted in a socket in one end to
open and close the jaws; and I insert the shank of the chuck in a socket holder f,
so that the chuck may be turned freely to present the different sides of the drill
point to the stone, and also that it may be shifted lengthwise to feed the drill as
the grinding progresses, with a slide bolt g, actuated by a spring h, to hold the
chuck in the two positions for properly presenting the said sides of the point to
the stone, the shank being suitably grooved or notched at opposite points i, for
reception of the taper end j, of the bolt, and the end of the shank projecting
through the holding socket has a screw threaded flange on which the internally
threaded ring m, works to feed the drill, said ring turning freely on the end of the
socket but held against lengthwise movement by the circumferential feather n,
inside of it, and in the corresponding groove in the socket in which the feather
works.
The slide bolt g is arranged in a laterally projecting arm o, of the socket which
is bored and the bolt is inserted from the opposite side of the socket, the hole
thereat being afterwards closed by a plug n if desired, and the knob p, for pulling
the bolt is attached to the projecting end of the bolt.
To the socket I attach a gauge plate q, constructed in the form of a segment of
a hollow cone constituting a rocking and sliding gauge suitably for gauging the
drills on the stone by lying on a flat table s, placed tangentially to the face of the
stone, with the point of the drill overhanging the edge of the table next to
the stone so as to have contact with it, and being rolled forward and backward,
and at the same time shifted forward and backward transversely to the way it
rolls.
This plate is so attached to the socket, that its axis is at u, to which the
edge t is radial, whilst the axis of the drill is in the line a-a, parallel to the line
of edge t, and back of it half the thickness of the metal at the central portion of
the point of the largest drill for which the tool is designed, so that the edge
of the drill to be ground will not project in advance of the edge t of the plate.

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The edges v, of drills of smaller size will fall a little short of said edge t, of the
gauge, and such may be the case with the largest without detriment, the axis of the
drill being set a little further back relatively to edge t, of the gauge.
The angle between the surface of the gauge plate and its axis is less on the side
of edge w, than on the side of edge t, as indicated in Figures 2 and 3, to produce
the proper clearance of the point of the drill.
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 :-
1. The combination of the socket holder, drill holding chuck in said holder, and
the segmental conic gauge plate attached to the socket holder, said chuck being
revoluble relatively to the plate and having a stop device to hold it in the positions
.required substantially as described.
2. The combination of the socket holder, drill holding chuck in said holder,
segmental conic gauge plate attached to the socket holder and the spring stop bolt,
said chuck being revoluble relatively to the gauge plate substantially as described.
3. The combination of the socket holder, drill holding chuck in said holder,
segmental conic gauge plate and the feed screw, said chuck being revoluble
relatively to the gauge plate and having a stop device to hold it in position
substantially as described.
4. The combination of the socket holder, drill holding chuck in said holder, and
segmental conic gauge plate the axis of the drill chuck being offset back of the
edge of the said plate gauging the cutting edge of the drill substantially as
.described.
5. The combination of the drill chuck, holding socket for said chuck, the segmental
conic gauge plate attached to said socket, the locking bolt for the shank of the chuck,
the feeding ring feathered on the socket, and the screw flange on the shank of the
chuck substantially as described.
Dated November 25th 1892.