CERTAIN NEW AND USEFUL IMPROVEMENTS, IN DRILL-CHUCKS
Year: 1884

page_text: JAMES HEWITT of 62 Sparkenlioe Street, Leicester, Manager of a Public Company
do hereby declare the nature of my Invention for CERTAIN NEW AND USEFUL
IMPROVEMENTS, IN DRILL-CHUCKS, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
Drill-chucks, as is well known, usually consist of a rotary hub or head, carrying
a number of radial jaws, over which is placed a conical sleeve, which screws down
upon the head; and thus forces or wedges the jaws inward to grasp the drill. The
jaws have been formed and arranged in a variety of ways; but they are usually
arranged in radial slots or sockets in the head and slide in direct radial lines to or -
from the central drill-socket, in the manner of simple wedges, and their grasping
power on the drill thus depends entirely on the wedging pressure by which they
are forced against the drill by the action of the conical screw-sleeve.
Now in my improved drill chuck the jaws are pivoted to the head tangential to
or outside of the drill, and they approach and bear upon the drill in the manner of
pawls, and the exterior of the jaws has a conical spiral surface to match with the
conical or wedging surface on the interior of the sleeve, by which they are forced
against the drill.
The inain feature of my Invention, as here outlined, not only produces a very
strong and simple chuck, but one in which the grasp is very powerful, for in this
case the grasp does not depend entirely on the wedging pressure of the conical
screw-sleeve, for the greater the torsional strain on the drill the greater is the grasp
of the jaws, which tend to enter or close upon the drill by the tendency of the drill
to rotate against the tangentially-presented edges of the pawl-jaws.
My Invention also consists in the special construction and arrangement of the
jaws and of the other parts in relation thereto, as hereinafter fully set forth.
In the annexed Drawings, Figure 1, presents a longitudinal section of my
improved chuck. Fig. 2 is a plan of the head and jaws below the line x x of Fig. 1,
with the conical sleeve removed. Fig. 3, is a sectional plan on the line oo of
Fig. 1, and Fig. 4. is a sectional plan lower down on the line y y.
:

page_text: In these Figures, a indicates the head or hub of the chuck, which, as usual, is
preferably formed with a central bore, b, which is enlarged and slightly tapered at
the base to receive the tapered shank of the tapered spindle c, which is driven into
the line-spindle of the lathe in the usual manner when the chuck is attached to
the lathe. This chuck-head a is much shorter than is usual, and is formed with a
flat top, a¹, which terminates within the cavity of the screw-sleeve e, at about the.
middle thereof, as seen in Fig. 1, while the sleeve screws on to the upper end of the
chuck-head in about the ordinary manner, as illustrated.
ddd indicate the grasping-jaws of the chuck, which, as usual, are preferably
three in number, arranged equidistant around the center of the chuck, as seen best
in Fig. 2. These jaws rise in isolated position from the flat,top of the chuck-head,
as will be understood from Figs. 1 and 2, instead of being arranged in radial slots
in the head, as is usual, and each jaw has a flat base or shoulder d', which seats on
the flat top of the chuck-head, as seen best in Fig. 1, and. from this shoulder a
pivotal stem or pintle, f, projects downward, and is journaled in a socket-hole bored
in the head, as best shown in Figs. 1, 3, and 4. Each jaw is thus hinged or pivoted
on the chuck-head at or near its circumference, and it will be noted, on reference
to Fig. 2, that the pivotal axis f of the jaws is at some lateral or circumferential
distance from the grasping-edges % of the jaws; and it will hence be noted that
the jaws are presented to the drill in a tangential direction, or in the manner of
pawls. Therefore if the jaws be forced against the drill their grasp thereon will be
very powerful, for not only will they seize it by virtue of the direct wedging
pressure by which they are forced by the sleeve against the drill, but in addition to
this the torsional strain on the drill, when turned in the direction of advance, as
indicated by the arrow in Fig. 2, will simply tend to tighten thie grasp of the pawl-
jaws, for the tendency of the jaws will be to enter the sides of the drill, as will be
readily understood in reference to Fig. 2, thus maintaining a powerful grasp upon
the drill, and preventing all slippage during the advance of the drill into
the work.
The outer sides, i, of the jaws opposite the grasping-edges h, as seen best in Figs. 1
and 2, are formed with an inclined or wedging surface, which matches with a
similar inclined or conical surface, kc, on the contracted mouth of the sleeve c, so
that as the sleeve is screwed downward the jaws are thus wedged together to grasp
the drill, as will be understood. The inclined surface i in the jaws is however
made a little twisting or spiral in its character, as shown in Fig. 2, in order to
match with the conical face k on the sleeve in the different positions in which the
jaws may be forced by the sleeve, for it will be noted that in this chuck the jaws
move in the arc of a circle struck from the center of the pintles f toward the center
of the drill, and hence require this spiral inclination, which would not be the case
where the jaws moved radially in or out. When the sleeve e is unscrewed a
spring,, causes the jaws to be diverged or thrown open to release the grasp on the
drill or to expand the opening of the jaws to receive a drill of larger size, as will be
understood. This spring 7, as seen best in Fig. 4, is a flat plate-spring coiled in a
single flat coil, and bears in deep flat notches m, cut on the middle of the pintles.
The spring is socketed in a circular recess, n, formed in the top of the chuck-head a,
and is held therein by a plug or disk, o, tightly driven into this recess, which plug
is turned off or recessed on its underside, so as to leave an annular socket for the
spring, as shown in Figs. 1 and 4.
It will also be seen on reference to Figs. 2, 3, and 4 that the holes for the
pivotal pintles are bored on the junctional line of the plug o with its socket.
Hence the notched sides of the pintles f project into the annular recess n, where
they are engaged by the spring 1, as seen in Figs. 1 and 4. It will hence be
understood that when the jaws are forced or turned inward the flatted or notched
part of their pintles will tend to bend the spring inward, and the reaction of this
spring will of course diverge or expand the jaws outward as soon as; the sleeve is
unscrewed, and, in addition to this opening action of the spring on the jaws, the
spring, as will be readily seen, also serves to hold the jaws in the head and prevent
0

page_text: them dropping out of place, even though the sleeve be entirely removed, which is
an important advantage over several existing chucks, in which the jaws and their
springs will fall out if the sleeve be unscrewed too far.
It will thus be seen by these features of construction I form a chuck which has
not only a very powerful and certain grasp, but possesses a really simple and
inexpensive construction, has no loose or detached parts, is compact in form, and
its working parts are not capable of being clogged by chips, as its joints and springs
are completely inclosed, thereby combining a number of important advantages.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is-
1. In a drill-chuck, the combination, with a sustaining chuck-head, of a series of
radially-arranged jaws pivoted on the chuck-head at or near the outer circumference
thereof, with their grasping ends presented tangentially inward toward the drill in
the manner of pawls, with an encircling sleeve screwing on to the chuck-head over
the said pawl jaws to wedge the same inwardly, substantially as hercin set forth.
2. The combination, with the chuck-head a, of the pivotal pawl-jaws d, having an
inclined or wedging surface, i, on their exterior, with the screw-sleeve e screwing
on to the chuck-head over the said jaws, substantially as herein shown and
described.
3. The combination, in a chuck with pivotal pawl-jaws, of the curved or coiled
spring, arranged to bear upon notched or flatted portions on the pivotal stems of
the pawl-jaws substantially as and for the purpose set forth.
4. The combination, in a chuck with pivotal pawl-jaws, of the spring 7, socketed
in a recess in the chuck-head, and the retaining plug o, driven into the same,
substantially as herein shown and described.
Dated this Seventeenth day of July 1884