An Improvement in Drill Chucks.
Year: 1891

page_text: COMPLETE SPECIFICATION.
An Improvement in Drill Chucks.
I, CHARLES THURBER PRATT, Machinist, of Clayville, in the County of
Oneida, State of New York, United States of America, do hereby declare the
nature of my invention for IMPROVEMENTS IN DRILL-CHUCKS, and in what
manner the same may be performed, to be particularly described and ascertained
by the following statement:-
My invention relates to improvements in drill-chucks, and the purpose of the
improvement is to provide means in the chuck for giving positive rotation to the
drill which is held in the chuck, independently of the jaws of the chuck, and at
the same time to permit said jaws to accurately align the said drill.
I achieve the first of said purposes by inserting into the body of the chuck a plate
which is slotted to receive the end of the drill stock. As the chuck revolves, the
said plate also revolves and by its engagement on the end of the drill stock revolves
the drill, thereby relieving the teeth of the jaws from the grinding and twisting
strain which they are subjected to when the grip of said jaws on the drill stock is
relied on alone to revolve the drill. The second of said purposes I achieve by
giving to said plate a certain amount of motion in the chuck, in a direction
transverse to the axis of rotation of the chuck. Were the said plate fixed in the
chuck, then when the said jaws had aligned the drill, if the end of the drill stock were
not accurately formed it would not enter the slot in the said plate; or if the end of
the drill stock were first inserted into said slot, then the jaws could not bring the
drill to a true alignment. Therefore, since the ends of drill stocks are not formed
with any special accuracy, it is necessary to give to the said plate a certain move-
inent in the chuck to compensate for the inaccuracy of the form of the drill stock.
I achieve this movement of said plate, by forming the chamber in the chuck in
which the said plate is inserted in such a manner that said plate has a certain
amount of play in said chamber, and such motion of the chuck may be either in a
curved line or in a straight line, but the plane of the said curved line, or the
direction of said straight line should be transverse to the axis of rotation of the chuck,
and by preference said plane and said direction should be perpendicular to said
axis of rotation. The said plate is applicable to many kinds of chucks, and its use
is not restricted to chucks of that special kind which is shown in the drawings that
accompany this statement.
Referring to said drawings,
Fig. 1, is an end view of the chuck, showing the jaws grasping the shank of
drill.
Fig. 2, is a cross section of the chuck on the line W-W of Fig. 4, showing the
screw which operates the jaws.
Fig. 3, is a cross section of the chuck on the line X-X of Fig. 4, showing the
form of the chamber which contains the movable plate, and said plate in position in
the chamber.
Fig. 4, is a longitudinal elevation of the chuck.
Fig. 5, is a longitudinal section of the chuck on the line Y-Y of Fig. 1, with the
jaws, screw, and movable plate removed, in order to show the form of the cavity in
the chuck.
Fig. 6, is a longitudinal section of the chuck on the line Z-Z of Fig. 1, the plane
of Fig. 6 being perpendicular to the plane of Fig. 5.
Fig. 7, is a plan of the movable plate.
Fig. 8, is a view of the jaws seen from below, and showing the threads for engaging
with the screw.
Figs. 9 and 94 show a broken elevation and also an end view of a drill.

page_text: The chick, A, is preferably constructed of steel and is in shape a cylinder, with
a conoidal part, B, which is bored axially at; B, to receive the arbor, B2, of the
lathe in which the chuck, A, is placed when it, is desired to drill.
In the said
chuck, A, is a recess C, formed with parallel side walls; as shown in Fig. 2, and
extending to a considerable depth into the chuck, A, that is to say extending nearly
back to the conoidal part, B, of said.chuck. At its innermost part, said recess, C.
is formed into a circular chamber, D, and said chamber, D; is concentric with the
axis of the arbor, 132, and the sail chamber, D, has a lateral passage, d, d, which
extends from said chamber, D, out to the external circumference of said chuck, A.
The said passage, d, d, is somewhat contracted outwardly, as seen in Fig. 3; to
certain points, d', d', which are near to the external surface of the chuck, A, as
shown in said Fig. 3, and said points, d', d, are of course eccentric to the arbor, B².
From the said points, d', d, the said passage, d, d, rounds with a convex curvature
into the outer surface of the chuck, as seen in Fig. 3, for the purpose of giving.
clearance for the rotation of the movable plate, E, in the manner hereinafter
described. In order to admit the plate, E, into the chamber, D, the aforesaid
recess, C, in the body of the chuck, A, is hollowed out on one side, as at i, in
Fig. 5, and said hollow is carried back to the chamber, D, and the hollow of the
opposite surface of the chamber D, is carried forward as at j, to the screw recess,
as shown in Fig. 5. The rear or innermost surface of the chamber, D, and the
passage, d, d, are plane surfaces, to permit of the free movement over them of the
aforesaid plate, E. Said plate E, is inserted into the chamber, D, and passage, d, d,
by way of the recess, C; and when said plate, E, is inserted in said chamber, D, it
takes the position shown in Fig. 3. Said plate E, is preferably a flat piece of
metal, of a thickness a little less than the depth of the chamber, D, and
passage, d, d, and said plate, E, is formed with a circular head, e, which is of lesser
diameter than said circular chamber, D, and with a rectangular arm, e, projecting
from one side of the said circular head, e, as clearly shown in Figs. 3 and 7.
said arm, e, has such a width 'as to just easily fit the narrowest part of the
passage, d, d. This relation of the plate, E, to the chamber, D, and passage, d, d,
is clearly shown in Fig. 3. The said circular head, e, of the plate, E, has a slot, e²,
centrally placed, in said head, and when the said plate, E, is in the chamber, D;
then said slot,, is in or approximately in the line of the axis of the arbor, B².
Now it is evident from the foregoing description. that the plate, E, can rotate to
either side about one of the points, d, d, as a centre, and also that said plate, E, can.
move in a rectilinear direction lengthwise of its arm, e', that is to say transverse to
the axis of rotation of the chuck, A. The amount of said motions is limited by the
head, e, of the plate, E, coming in contact with the walls of the circular chamber, D,
and in practice a very small movement of said plate E, is sufficient to compensate
for all inequalities in the form of the drill.
The
The drawings show the said plate, E, applied to a chuck in which there are two
sliding jaws, F, F, which are operated by a screw, G. Said jaws, F, F, are placed
in the aforesaid recess; C, which as said is formed with parallel side walls, and in
said side walls are formed guides, c, c, which enter slots, f, in each of the
jaws, F, F. Each of said jaws, F, F, is formed on its under side with a segment:of
a female screw, ff, and the threads of the segment of one jaw are right hand
threads, and the threads of the other jaw are left hand threads of equal pitch..
The said screw threads, ',, engage with the sections of a screw, G, which is
formed of two parts, g, g', one with right hand and the other left hand threads, as
shown in Fig. 1, which parts, . ', are connected by a spindle, g, of lesser diameter
than the said parts, g, g'. The said screw, G, is placed in a semi-cylindrical
recess, H, which passes transversely through the chuck, A, and is of: size to freely
admit the screw, G. Said recess H; has a smooth wall, so as not to engage with
the threads of the screw, G, and at its middle part corresponding to the position of
the spindle, g, of the screw, G, the said recess, H; is formed, with a semi-
cylindrical collar, h, which just fits the said spindle, 92. Thus when, the screw G
is in the recess, II, the spindle, g², rests in the collar, h, and the said screw G; is
?

page_text: free to rotate, but cannot move lengthwise. On one end of the screw, G, there is a
shank, g³, to receive a key by which the screw G, is turned. So it is evident that
if the jaws, F, F, are inserted into the recess, C, until their threads, ", 1", catch
the threads of the screw G, and the said screw G is turned in one direction the
said jaws F, F, will approach each other until they meet in the middle of the.
chuck, A. The meeting faces of said jaws F, F, are formed with V-shaped
teeth,, and the teeth of one jaw may be placed opposite the interval between the
teeth of the other jaw. I use a drill, K, with its end flattened to a rectangular
form, as shown in Fig. 94, at K, and said rectangle, K, is of a size to easily fit the
slot in the plate, E.
The operation is as follows:
The jaws, F, F, being opened sufficiently to admit the drill, K, said drill is
inserted between the jaws, F, F, and the flattened end K, is placed in the slot, e³,
in the plate, E. Then by turning the screw G the jaws F, F, are tightly closed
on the stock of the drill K, as seen in Fig. 1, and the drill, K, is thereby brought
to a true alignment. Should the flattened end of the drill K, not be truly in the
centre of the drill K, then the plate E, will move a little one way or the other to
compensate for the irregularity of the flattened end K.
The chuck being revolved in the ordinary manner in a suitable lathe then the
plate E will revolve the drill, and thus relieve the jaws F, F, from the strain
which comes on them when they are relied on alone to revolve the drill. Indeed
with my chuck said jaws F, F, serve principally to align the drill accurately, but
are not needed to revolve the drill.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare what I
claim is:
1. A drill chuck having a central chamber with a lateral passage that extends in
a direction transverse to the axis of rotation of the chuck, and a slotted plate
loosely inserted into said chamber and passage and being capable of motion therein
in a direction transverse to the said axis of rotation of the chuck.
2. A drill chuck having a central chamber with a lateral passage which is
contracted outwardly from the axis of rotation of said chuck, and a slotted piece
loosely inserted into said chamber and passage, and being rotatable about the points
of greatest contraction of said passage.
3. In a drill chuck, a plate slotted to receive the end of a drill, and being
capable of motion in the chuck in a direction transverse to the axis of rotation
thereof.
4. The combination of a drill chuck having a central chamber with a lateral
passage, a slotted plate loosely inserted into said chamber and passage and
being capable of motion therein in a direction transverse to the axis of rotation
of said chuck, and a drill with flattened end for insertion into the slot in the
said plate.
Dated this 1st day of April 1891.
WHEATLEY & MACKENZIE,
40, Chancery Lane, W.C., Agents.