IMPROVE IN MACHINERY FOR MAKING TWIST DRILLS
Year: 1866

page_text: of Middlesex, Engineer and Patent Agent, for the
IMPROVE
IN MACHINERY FOR MAKING TWIST DRILLS."-A communication
from abroad by Andrew Reynolds Arnold, of Newark, Essex County,
State of New Jersey, United States of America. "
PROVISIONAL SPECIFICATION left by the said William Clark at the
Office of the Commissioners. of Patents, with his Petition, on the 25th
- April 1866.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer and Patent Agent, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN MACHINERY FOR MAKING TWIST DRILLS," to be as
follows:-
In the accompanying Drawings Figure. I is a front elevation, Figure 2 is a
side elevation. Figure, 3 is a vertical section (at, x, Figure 2.) in the plane
of the axis of the mandril;. Figure 4, a section (at. y.. y, Figure 2,) in the
plane, of the axis of one of the burr. cutters to exhibit the arrangement of .the
gearing for driving the burr.cutters: Figure 5 a top view. of the modification
for finishing the grooves of twist drills; Figure 6, a vertical section in the
plane of one of the cutters; Figures 7 and 8, side elevation, and end view of
a twist drill, as grooved by the burr cutters; Figure, 9, an end view of such a
drill or cutter when finished; Figure 10, an end view of Figure 5; Figure 11
is an axial section of a twist drill; Figure 12 is a front view of an auxiliary
framed, on which are mounted cutters for reducing the periphery at the
[Price Sd.]

page_text: back of the front spiral edges of the drills; Figure 13 is a plan of the said
frame and its appurtenances; Figure 14 is a plan or face view; and
Figure 15 is a side view of a backing cutter, which may be operated by the
same devices that operate the cherry cutters. Similar letters of reference indi-
cate corresponding parts.
'The object of this Invention is to cut or finish the two grooves which form
what is termed a iwist drill at one and. the same operation, by two cutters
acting simultaneously on opposite sides of the blank, that the two may
counteract each other. and thereby avoid all tendency to spring the blank;
and also to reduce and milk off the periphery of the drill at the back of the
front spiral edges, so that it will not bind when used for drilling a hole.
In the accompanying Drawings a represents a suitable frame, and b the
blank or cylindrical rod of steel which is being formed or cut; the lower end
of this blank is inserted in a central socket at the upper end of a cylindrical
mandrilc which is fitted to turn and slide longitudinally in suitable boxes in
the two cross bars d and e of the frame, and it also slides longitudinally in the
eye of a cog wheel, to which it is feathered, so as to be turned by it; a slow
rotary motion is imparted to the mandril .c by a worm g on the horizontal
driving shaft h, which carries a cone pulley i to receive a band from some
motor. The worm g drives a worm wheel i, at the lower end of a vertical
shaft, which carries a pinion 1, and this pinion, by the train of wheels and
pinion m, n, o, drives the wheel on the mandril c. In this way a slow
rotary motion is given to the mandril and the blank b' which it carries, which
rotary motion can be increased or diminished at pleasure by the cone pulley.
Whilst the mandril is rotated, as above described, it is gradually lifted by a
regular motion derived from the same source as the rotary motion. The
worm wheel at the lower end of the vertical shaft drives a cog wheel p, on
the lower end of a shaft q, and the upper end of this shaft is threaded and
fitted to the lower end of the mandril c, which is made hollow and threaded
for that purpose.
The cog wheel and pinion n, o, before described, are
mounted and turn on a stud projecting from a bracket r attached to the
frame by a screw bolt passing through an elongated slot, or otherwise con-
nected to admit of adjustment, so that they can be taken off and others of
a different size substituted to vary the relative speed of the rotary and longi-
tudinal motions of the mandril c, and thereby admit of making the twist to be
cut of any desired pitch.
The operation of cutting the twist on the blank is performed whilst the
mandril is rising, and at the end of this upward motion the worm g on the
driving shaft is thrown out of gear with the worm wheel by a cam s on the

page_text: mandril, which then pushes a slide on the under side of the cross bar d of
the frame. One end of the driving, or worm shaft h is mounted in the lower
arm of a lever u which turns on a fulcrum pin v. The upper arm of this lever
has sufficient spring to be held in place by a shoulder or catch on the frame
while the worm is in gear, but when the slide t is pushed out by the cam s
it disengages the upper arm of the lever u, and the lower arm is then forced
outward by a spring e to throw the worm out of gear; after this disengage-
ment of the worm the mandril can be run down rapidly by a crank handle a
on a short horizontal shaft b', which communicates motion by the bevil cog
wheels c, c, to the vertical shaft k. To the top of the cross bar d or cap of
the main frame is secured by screws or other suitable means an auxiliary
framed, on the top of which are mounted two poppets e', e', which slide
horizontally in parallel ways. In each poppet is mounted an inclined arbor or
spindle which carries at its lower end a burr cutter g', the cutting edge of
which is rounded to suit the form of groove to be cut in the blank. The
inclination of these two arbors is to be such that the inclination of the planes
of the two burr cutters shall correspond with the pitch of the twist to be cut
in the blank, and the two arbors are inclined in opposite directions. As it is
desirable to set the machine for cutting twist augers of different twist, the
boxes in which the arbors or spindles are mounted are attached to the
poppets by screw bolts passing through elongated slots. In this way the
arbors can be set at any desired inclination.
carries a bevil cog
wheel
wheel
Each arbor
at its upper end, which meshes into the cogs of another bevil cog
that turns on a stud pin j¹. The opposite face of the bevil wheel i
is a rim with cogs on its inner periphery which engages the cogs of two
pinions l', ', that turn on stud pins arranged on opposite sides of the axis of
the bevil wheel, and which are attached to a plate m' on the stud pin i¹, on
which the bevil wheel turns. The pulley n¹, by which the arbors are driven
by a belt from some motor, is mounted to turn on the stud pin j', and on its
inner face it carries a pinion o¹ which drives the two pinions 1, 1, and these in
turn drive the bevil cog wheel i, which is cogged on its inner periphery k',
and this bevil wheel drives the arbor. The inner face of the pulley n' which
carries the pinion o' may be made of enlarged diameter, with a rim p' extending
over the rim of the bevilled wheel, and the outside of this rim is in the form
of and can be used as a pulley when desired. The burr cutters are arranged
and operate on opposite sides of the blank, each cutting one groove, and in
this way I am enabled not only to cut the twist in one half the time heretofore
required, but to avoid all tendency to spring the blank, a difficulty heretofore
experienced, and which cannot take place in this arrangement, as the cutters

page_text: in their action counteract each other. The poppets which carry the two
burr cutters, as before stated, slide in parallel ways, and each is set to the
depth of the cut to be made by an adjustable guage q'. Before starting the
machine each poppet is pushed against-its gnage.
The grooves forming the twist drill are of the greatest depth at the cutting
end of the drill, and of gradually less depth towards the shank, as represented
by dotted lines in the separate Figure 11 representing a section of such a
drill. On account of the gradually reduced depth of the grooves of the .drill
the burr cutters are gradually moved from the axis of the blank as it rises
during the operation. To effect this motion of the cutters there is a collar r
on the upper end of the mandril c, and which for adjustment can be shifted
and fastened by a temper screw at any desired distance from the upper end
of the mandril. A lever that turns on a fulcrum pin at bears by a roller
or pin on the surface of the collar r', and therefore that end of the said lever
will be elevated as the mandril rises. The opposite end of the lever is slotted
and embraces an adjustable pin ' on the lower end of a sliding cogged rack c
which engages the cogs of a pinion c¹ on the end of a screw shaft z mounted
on the top of the auxiliary frame d', and the thread on this shaft engages and
slides the poppet, so that as the mandril with its collar r' rises the lever
depresses the cogged rack which turns the screw shaft, and this in turn slides
the poppet with the burr cutter gradually from the axis of the blank. When
the operation is completed the rack is disengaged from the pinion on the screw
shaft to admit of moving back the poppet to its place of starting against the
guage q¹ by a crank handle y'. This disengagement of the rack is effected
by turning a button situated behind the rack. To adjust the parts to
increase or decrease the range of motion the fulcrum pin on which the lever s'
vibrates is adjustable in a slot of the bracket from which it projects, so that it
can be set near to or farther from that end of the lever which bears on the
collar, and in like manner the pin which is acted upon by the other arm of
the lever is fitted and secured in a slot in the lower end of the cogged rack.
The other poppet is provided with a like arrangement. The parts being
adjusted, the mandril let down, a blank inserted, and the poppets of the burr
cutters set up against their guages, and the machine started, the mandril will
rise gradually to present the point of the blank to the burr cutters, which
gradually cut the two grooves as the mandril continues to raise and turn the
blank, both motions being so timed and proportioned as to give the desired
twist to the two grooves, and as these motions proceed the two burr cutters
are gradually moved from the axis of the blank to reduce the depth of cut,
and in this way and at one operation the two grooves to form a twist drill are

page_text: cut. simultaneously and without strain on the rod of steel. The cutting edges
formed on the end of the twist drill by reason of the form of the grooves made
by the burr cutters will be curved, and as it is desirable to have such cutting
edges straight subject the formed drill to a second operation in the
same machine substituting what are known as cherry cutters for the burr
cutters above described. The mode of applying the cherry cutters is repre-
sented in Figures 5 and 6. For convenience take off the auxiliary frame
above described from the main frame and substitute therefore the auxiliary
frame a which is in all essential respects like it. The poppets b. b. slide in
parallel ways on the top, and these are adjusted by screw shafts ², c, with
crank handles. The cherry cutters d, d. are semi-spherical at their front.
ends and conical at their rear ends; they are secured in the front ends of two
arbors e. e. cach carrying a cone of pulleys to receive the driving belt.
Each mandril is fitted to turn in a sleeve g, the outer periphery of which is
threaded and tapped in the poppet, and the outer end of the sleeve is provided
with a cog wheel which engages and is turned by a cog rack connected
with the lever operated by the collar on the mandril c. as already
described, for cutting the grooves of gradually less depth with the burr
cutters. By the arrangement last described the two grooves cut by the burr
cutters are enlarged. the semi-spherical end of the cherry cutters finishing the
bottom of the two grooves which form the twist drill, and the conical part of
the cutters forming the sides of the grooves, so that when the end of the drill
is ground off to a bevil the cutting edges thereby formed will be straight. In
order to prevent the drill from binding when drilling a hole in a piece of
work it is necessary to mill off the periphery at the back of the front or cutting
spiral edges. Two methods of accomplishing this are here set forth, one of
which is illustrated by Figures 12 and 13, and the other by Figures 14 and
15, the latter representing a peculiar form of cutter, which may be used in
conjunction with the arbors e" that hold the cherry cutters.
་
In order to apply the 'modification shown in Figures 12 and 13. I take off
the auxiliary frame from the main frame and substitute therefor the
auxiliary frame . which has poppets a, a, sliding in ways on the top of the
frame d', and adjusted by screw shafts e, e. with crank handles. The backing
cutters are cylindrical with teeth inclined at an angle of about forty-five
degrees with their axes. They are mounted on upright shafts, which have
their bearings in pendulous frames f, f', placed conversely on the sides of the
poppets. The said frames are suspended from the ends of the stationary
shafts n", n, of the cone pulleys s³, s, that is to say, from the ends which go
through the poppets. The said pulleys are rotated by bands from any con-

page_text: venient motor, and are made hollow, but have central hubs which slip over
the shafts, and are held thereon by nuts or other convenient means. On
the inner end of the hub of each pulley is a pinion o", which engages with four
gear wheels q set radially around the shaft n, and supported on short shafts
that project backward from stationary plates within the hollow bevil gears m",
which plates embrace and are fast on the shafts n. The said shafts are sup-
ported at their rear ends by an annular plate , through whose central opening
the pinion o³ of the pulley is free to pass. Each of the said short shafts has
on it a small pinion p, which engages with cog teeth formed on the inner
circumference of the hollow gear m³, and consequently when the pulley is
revolved its motion is communicated to the gears q", and thence through the
pinions p to the bevil gear m³, whose bevil teeth engage a bevil gear placed
on a short vertical shaft on the top of the pendulous frame f, the lower end
of the said vertical shaft having on it a pinion K", which engages a gear
wheel on the upper end of the spindle of the cutter g, the said spindle
turning in proper bearings on the inner side or edge of the said pendulous
frame. The pendulons frames are swung on their pivots, which, as before
stated, are the shafts of the cone pulleys, so as to bring the cutters
desired position for the operation of "backing" a drill, and are held in such
position by means of clamping nuts that go through elongated slots in the
frame, and enter the poppets. This description applies to each poppet and
pendulous frame, each frame having its cutter g operated in the same manner.
The movements of the poppets inwards are determined by the adjusting screws
c, c, so as to suit drills of different diameters.
to the
The arrangement of gearing above described, by which the motions of the
cone pulleys are communicated to the spindles of the cutters g³, is intended to
reduce the speed so as to give a comparatively slow rotation to the said cutters
as compared with that of the pulleys, and also to bring the gearing within
a small space.
The cutters having their teeth inclined as above stated
(their inclination being towards the direction of rotation of the cutters so as
to hold the drill down in the socket of the mandril, and being also swung so
that their upper edges are nearer the centre of the drill than the lower edges,
it follows that when they are rotated by means of the rotation of the cone
pulleys s', s, and the gearing shown in Figures 12 and 13 intermediate the
pulleys and the spindles of the cutters, the drill being also rotated and moved
longitudinally at the proper speed by means of the devices above set forth, which
advance the drill blank when under the operation of the burr and cherry
cutters; these surfaces of the spiral peripheries of the drill, which are
presented to the advanced corners or portions of the cutters, will be milled off

page_text: on a bevil behind the front edges of the spiral surfaces. thereby reducing that
part of the diameter of the drill which is behind the front edges, leaving the
front edges the full diameter. The revolutions of the cutters . . and the
rotary and longitudinal motions given to the drill are adjusted for each other,
so that the spiral periphery of the drill on both sides will be continually
presented to the cutters, each cutter g³ operating on the same spiral division of
the periphery throughout the whole extent of its spiral course. In consequence
of the angle at which the cutters are presented they will mill off that portion
of the back which is behind the line of the front edge of cach side of the drill,
leaving the front the full diameter of the drill. Since both backs are acted on
at the same time it is clear that the drill will not be sprung or bent, the
cutters serving to counteract each other, as explained, with reference to the
burr cutters. The same result can be attained by the use of the face cutter g*,
shown in Figures 14 and 15, which are respectively a side and end view
thereof. Two such cutiers are used so as to operate at the same time on two
opposite spiral surfaces of a drill. They are placed in the same arbors e², e²,
see Figures 5 and 6, which receive the cherry cutters, the latter being removed
when the backing cutters are to be used, but it is necessary that the faces of
the cutters be set at an angle so as to mill off the spiral surface continuously
behind the front edge of the drill, the upper part of the face of each cutter
being set towards the centre of the drill for the same reason that the cutters ³
are so set. The adjustment of the parts that receive the said cutters g', so as
to incline their faces, is accomplished by making the heads that carry the
mandril capable of being set obliquely on their supports.
I have thus described and represented the mode of construction which I
have tried with success and which I prefer; but I do not wish to be under-
stood as limiting the claim of Invention to such mode of application, as it
may be varied by the substitution of mechanical equivalents having the same
made a aporation
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the 24th
October 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer and
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fifth day of April, in the year of our Lord Onc

page_text: thousand eight hundred and sixty-six, in the twenty-ninth year of Her reign,
did, for Herself. Her heirs and successors, give and grant unto me, the said
William Clark, Her special licence that I, the said William Clark, my executors,
administrators, and assigns. or such others as I, the said William Clark,
my executors, administrators, and assigns, should at any time agree with, and
no others. from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and vend.
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN MACHINERY FOR
MAKING TWIST DRILLS," a communication to me from abroad by Andrew
Reynolds Arnold, of Newark, Essex County, State of New Jersey, United
States, of America. upon the condition (amongst others) that I, the said
William Clark, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great Seal
Patent Oflice within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said William Clark, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the three Sheets of Drawings hereunto
annexed, and to the letters and figures marked thereon (that is to say):-
Figure 1 is a front elevation; Figure 2, a side elevation; Figure 3, a
vertical section (at 2. 2. Figure 2), in the plane of the axis of the mandril;
Figure 1. a section (at y, y, Figure 2), in the plane of the axis of one of the
burr cutters, to exhibit the arrangement of the gearing for driving the burr
cutters; Figure 5 is a top view of the modification for finishing the grooves
of twist drills; Figure 6, a vertical section in the plane of one of the cutters;
Figures 7 and 8, side elevation and end view of a twist drill as grooved by
burr cutters; Figure 9, an end view of such a cutter when finished; Figure
10, an end view of Figure 5; Figure 11 is an axial section of a twist drill;
Figure 12 is a front view of an auxiliary frame d, on which are mounted
cutters for reducing the periphery back of the front spiral edges of the drills;
Figure 13 is a plan of said frame and its appurtenances; Figure 14 is a
plan or face view, and Figure 15 is a side view of a backing cutter which may
Similar
be operated by the same devices that operate the cherry cutters.
letters of reference indicate corresponding parts.
The object of this Invention is to cut or finish the two grooves which form

page_text: what is termed a twist drill at one and the same operation by two cutters
acting simultaneously on opposite sides of the blank, so that the two may
counteract each other, and thereby avoid all tendency to spring the blank, and
also to reduce and mill off the periphery of the drill back of the front spiral
edges, so that it will not bind when used for drilling a hole.
on the horizontal
band from some
In the accompanying Drawings a represents a suitable frame, and 6 the
blank or cylindrical rod of steel which is being formed or cut; the lower end
of this blank is inserted in a central socket at the upper end of a cylindrical
mandril c which is fitted to turn and slide longitudinally in suitable boxes in
the two cross bars d and e of the frame, and it also slides longitudinally in
the eye of a cog wheel, to which it is feathered, so as to be turned by it; a
slow rotary motion is imparted to the mandril c by a worm
driving shaft h, which carries a cone pulley i to receive a
motor. The worm g drives a worm wheel i, at the lower end of a vertical
shaft, which carries a pinion 1, and this pinion, by the train of wheels and
pinion m, n, o, drives the wheel on the mandril c. In this way a slow
rotary motion is given to the mandril and the blank b, which it carries, which
rotary motion can be increased or diminished at pleasure by the cone pulley.
Whilst the mandril is rotated, as above described, it is gradually lifted by a
regular motion derived from the same source as the rotary motion. The
worm wheel at the lower end of the vertical shaft k drives a cog wheel p, on
the lower end of a shaft q, and the upper end of this shaft is threaded and
fitted to the lower end of the mandril c, which is made hollow, and threaded
for that purpose. The cog wheel and pinion n, o, before described. are
mounted and turn on a stud projecting from a bracket attached to the frame
by a screw bolt passing through an elongated slot, or otherwise connected to
admit of adjustment, so that they can be taken off and others of different
sizes substituted to vary the relative speed of the rotary and longitudinal
motions of the mandril c, and thereby admit of making the twist to be cut of
any desired pitch. The operation of cutting the twist on the blank is per-
formed whilst the mandril is rising, and at the end of this upward motion the
worm g on the driving shaft is thrown out of gear with the worm wheel
a cam s on the mandril, which then pushes a slide on the under side of the
cross bar of the frame. One end of the driving or worm shaft
in the lower arm of a lever u which turns on a fulcrum pin c.
arn of this lever has sufficient spring to be held in place by a shoulder or
catch on the frame while the form is in gear, but when the slide t is pushed
out by the cam s it disengages the upper arm of the lever u, and the lower
arm is then forced outwards by a spring wo to throw the worm out of gear;
by
is mounted
The upper

page_text: or other
that turns on a
is a rim with
after this disengagement of the worm the mandril can be run down rapidly
by a crank handle a' on a short horizontal shaft. b. which communicates
motion by the bevil cog' wheels c', c', to the vertical shaft k. To the top of
the cross bar d, or cap of the main frame. is secured by screws
suitable means an auxiliary frame, d', on the top of which are mounted two
poppets e', e', which slide horizontally in parallel ways. In each poppet is
mounted an inclined arbor or spindle f, which carries at its lower end a burr
cutter g, the cutting edge of which is rounded to suit the form of groove to
be cut in the blank. The inclination of these two arbors is to be such that
the inclination of the planes of the two burr cutters shall correspond with the
pitch of the twist to be cut in the blank, and the two arbors are inclined in
opposite directions. As it is desirable to set the machine for cutting twist
augers of different twist, the boxes in which the arbors or spindles f
are mounted are attached to the poppets by screw bolts passing through
elongated slots. In this way the arbors can be set at any desired incli-
nation. Each arbor carries a bevil cog wheel at its upper end.
which meshes into the cogs of another cog wheel
stud pin 7'. The opposite face of the bevil wheel
cogs on its inner periphery which engages the cogs of two pinions 1, 1,
that turn on stud pins arranged on opposite sides of the axis of the bevil
wheel, and which are attached to a plate m' on the stud pin on which
the bevil wheel i turns. The pulley by which the arbors are driven by
a belt from some motor is mounted to turn on the stud pin and on its
inner face it carries a pinion o' which drives the two pinions I, l', and these
in turn drive the bevil cog wheel i which is cogged on its inner periphery k¹,
and this bevil wheel drives the arbor. The inner face of the pulley
which carries the pinion o may be made of enlarged diameter with a rim pl
extending over the rim of the bevilled wheel, and the outside of this rim is in
the form of and can be used as a pulley when desired. The burr cutters are
arranged and operate on opposite sides of the biank, each cutting one groove,
and in this way I am enabled not only to ent the twist in one half the time
heretofore required but to avoid all tendency to spring the blank, a difficulty
heretofore experienced, and which cannot take place in this arrangement as
the cutters in their action counteract each other. The poppets which carry
the two burr cutters, as before stated. slide in parallel ways, and each is set to
the depth of cut to be made by an adjustable gauge q'. Before starting the
machine each poppet is pushed against its gauge. The grooves forming the
twist drill are, of the greatest depth at the cutting end of the drill, and of
gradually less depth towards the shank, as represented by dotted lines in the

page_text: separate Figure 11 representing, a section of such a drill. On account
of the gradually reduced depth of the grooves of the drill the burr cutters are
gradually moved from the axis of the blank as it rises during the operation.
To effect this motion of the cutters there is a collar on the upper end of the
mandril c, and which for adjustment can be shifted and fastened by a temper
screw at any desired distance from the upper end of the mandril. A lever st
that turns on a fulcrum pin at bears by a roller or pin on the surface of the
collar r', and therefore that end of the said lever will be elevated as the man-
dril rises. The opposite end of the lever is slotted and embraces an adjustable
pin u on the lower end of a sliding cogged rack which engages the cogs of
a pinion won the end of a screw shaft z mounted on the top of the auxiliary
frame d', and the thread on this shaft engages and slides the poppet, so that
as the mandril with its collar ¹ rises the lever depresses the cogged rack.
which turns the screw shaft, and this in turn slides the poppet with the burr
cutter gradually from the axis of the blank. When the operation is completed
the rack is disengaged from the pinion on the screw shaft to admit of moving
back the poppet to its place of starting against the gauge q¹ by a crank
handle y'. This disengagement of the rack is effected by turning a button z¹
situated behind the rack. To adjust the parts to increase or decrease the
range of motion the fulcrum pin on which the lever s vibrates is adjustable in
a slot of the bracket from which it projects, so that it can be set near to or
farther from that end of the lever which bears on the collar, and in like
manner the pin which is acted upon by the other arm of the lever is fitted
and secured in a slot in the lower end of the cogged rack. The other poppet
is provided with a like arrangement. The parts being adjusted, the mandrit
let down, a blank inserted, and the poppets of the burr cutters set up against
their gauges and the machine started, the mandril will rise gradually to pre-
sent the point of the blank to the burr cutters, which gradually cut the two
grooves as the mandril continues to raise and turn the blank, both motions
being so timed and proportioned as to give the desired twist to the two
grooves, and as these motions proceed the two burr cutters are gradually
moved from the axis of the blank to reduce the depth of cut, and in this way
and at one operation the two grooves to form a twist drill are cut simul-
taneously and without strain on the rod of steel. The cutting edges formed
on the end of the twist drill by reason of the form of the grooves made by the
burr cutters will be curved, and as it is desirable to have such cutting edges
straight I subject the formed drill to a second operation in the same machine,
substituting what are known as cherry cutters for the burr cutters above
described.

page_text: The mode of applying the cherry cutters is represented in Figures ŏ and 6.
For convenience I take off the auxiliary frame above described from the main
frame and substitute therefor the auxiliary frame a², which is in all essential
respects like it.
The poppets b², 62, slide in parallel ways on the top, and
these are adjusted by screw shafts c, c², with crank handles. The cherry
cutters d³, d, are semispherical at their front ends and conical at their rear
ends. They are secured in the front ends of two arbors e², e², each carrying a
cone of pulleys to receive the driving belt. Each mandril is fitted to turn
threaded and tapped in the
in a sleeve g, the outer periphery of which is
poppet, and the outer end of the sleeve is provided with a cog wheel h* which
engages and is turned by a cogged rack connected with the lever 12 operated
by the collar r on the mandril c, as already described for cutting the grooves
of gradually less depth with the burr cutters. By the arrangement last.
described the two grooves cut by the burr cutters are enlarged, the semi-
spherical end of the cherry cutters finishing the bottom of the two grooves
which form the twist drill and the conical part of the cutters forming the sides
of the grooves, so that when the end of the drill is ground off to a bevil the
cutting edges thereby formed will be straight. In order to prevent the drill
from binding when drilling a hole in a piece of work it is necessary to mill off
the periphery back of the front or cutting spiral edges. Two methods of
accomplishing this are here set forth, one of which is illustrated by Figures 12
and 13, and the other by Figures 14 and 15, the latter representing a peculiar
form of cutter which may be used in conjunction with the arbors e³ that hold
the cherry cutters.
In order to apply the modification shown in Figures 12 and 13, I take off the
auxiliary frame a from the main frame, and substitute therefor the auxiliary
frame d³, which has poppets a³, a³, sliding inways on the top of frame ³, and
adjusted by screw shafts e3, e3, with crank handles. The backing cutters are
cylindrical, with teeth inclined at an angle of about 45 degrees with their
axes. They are mounted on upright shafts which have their bearings in
pendulous frames f, f, placed conversely on the sides of the poppets. Said
frames are suspended from the ends of the stationary shafts n³, n³, of the cone
pulleys, s3, that is to say, from the ends which go through the poppets. The
said pulleys are rotated by bands from any convenient motor, and are made
hollow, but have central hubs, which slip over the shaft n", and are held
thereon by nuts or other convenient means. On the inner end of the hub of
each pulley is a pinion o³, which engages with four gear wheels q³ set radially
around the shaft n³, and supported on short shafts that project backwards from
stationary plates within the hollow bevil gears m³, which plates embrace and

page_text: "
are fast on the shafts n³. The said shafts are supported at their rear ends
by an annular plate , through whose central opening the pinion o³ of the
pulley is free to pass.
Each of said short shafts has on it a small pinion ³.
which engages with cog teeth formed on the inner circumference of the hollow
gear m, and consequently when the pulley is revolved its motion is com-
municated to the gears q, and thence through the pinions p to the bevil
gear m, whose bevil teeth engage a bevil gear placed on a short vertical
shaft on the top of the pendulous frame f, the lower end of said vertical shaft
having on it a pinion, which engages a gear wheel on the upper end of
the spindle of the cutter g". said spindle turning in proper hearings on the
inner side or edge of said pendulous frame. The pendulous frames are swung
on their pivots, which as before stated are the shafts of the cone pulleys, so as
to bring the cutters g³ to the desired position for the operation of "backing"
a drill, and are held in such position by means of clamping nuts ³, that go
through elongated slots in the frame, and enter the poppets. This descrip-
tion applies to each poppet and pendulous frame, each frame having its
cutter operated in the same manner. The movements of the poppets
inwards are determined by the adjusting screws c, c, so as to suit drills of
different diameters. The arrangement of gearing above described by which the
motions of the cone pulleys are communicated to the spindles of the cutters g³
is intended to reduce the speed so as to give a comparatively slow rotation to
the said cutters as compared with that of the pulleys, and also to bring the
gearing within a small space. The cutters having their teeth inclined as
above stated (their inclination being towards the direction of rotation of the
cutters so as to hold the drill down in the socket of the mandril) and being
also swung so that their upper edges are nearer the centre of the drill than
the lower edges, it follows that when they are rotated by means of the rotation
of the cone pulleys &,, and the gearing shown in Figures 12 and 13 inter-
mediate of the pulleys and the spindles of the cutters, the drill being also
rotated and moved longitudinally at the proper speed by means of the devices
above set forth, which advance the drill blank when under the operation of
the burr and cherry cutters, these surfaces of the spiral peripheries of the
drill which are presented to the advanced corners or portions of the cutters
will be milled off on a bevil behind the front edges of the spiral surfaces,
thereby reducing that part of the diameter of the drill which is behind the
front edges, leaving the front edges the full diameter. The revolutions of
the cutters g, g³, and the rotary and longitudinal motions given to the drill
are adjusted for each other so that the spiral periphery of the drill on both

page_text: sides will be continually presented to the cutters, each entier g operating on
the same spiral division of the periphery throughout the whole extent of its
spiral course. In consequence of the angle at which the cutters are presented.
they will mill off that portion of the back which is behind the line of the
front edge of each side of the drill, leaving the front the full diameter of the
drill. Since both backs are acted on at the same time, it is clear that the
drill will not be sprung or bent, the cutters serving to counteract each other
as explained of the burr cutters. The same result can be attained by the use
of the face cutter g', shown in Figures 14 and 15, which are respectively a
side and end view thereof. Two such cutters are used so as to operate at the
same time on two opposite spiral surfaces of a drill: they are placed in the
same arbors e, e, see Figures 5 and 6, which receive the cherry cutters, the
latter being removed when the backing cutters are to be used, but it is neces-
sary that the faces of the cutters he set at an angle so as to mill off the spiral
surface continuously behind the front edge of the drill, the upper part of the
face of each cutter being set towards the centre of the drill for the same reason
that the cutters g are so set. The adjustment of the parts that receive the
said cutters g' so as to incline their faces is accomplished by making the heads
that carry the mandril capable of being set obliquely on their supports.
I have thus described and represented the mode of construction which 1
have tried with success, and which I prefer, but I do not wish to be understood
as limiting the claim of Invention to such mode of application, as it may be
varied by the substitution of mechanical equivalents having the same mode of
operation.
Having described the nature of this Invention and the manner of performing
the same. I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is,-
1st, the arrangement of the two rotating cutters, whether for cutting or
finishing the two grooves, and acting simultaneously on opposite sides of the
blank, substantially as described, in combination with the mandril for carrying
the blank, and having a simultaneous longitudinal and rotary motion, sub-
stantially as described, whereby I am enabled to cut or finish both grooves at
the same time and of the required pitch without tendency to spring the blank,
as set forth.
2ndly, also moving the cutter or cutters gradually from the axis of the
blank to make the groove or grooves of gradually less depth by means of the
sliding poppet (or poppets) in which the cutter (or cutters) is mounted, the
sliding mandril with a collar or the equivalent thereof, and the mechanism or

page_text: the equivalent thereof. by which the rising of the mandril communicates the
required motion to the poppet for cutting the grooves of gradually less depth
as set forth.
Brdly, the arrangement of gearing for communicating rotary motion from
the shaft to the wheel o in which the mandril c slides, and to which it is
feathered so as to be turned thereby in combination with the rotating screw
shaft g, which receives motion from the shaft , and which imparts the required
longitudinal motion to the mandril c. substantially as and for the purpose
specified.
4thly, the combination and arrangement of gearing herein described for
transmitting motion from the driving pulleys n' to the burr cutters g.
5thly, the backing cutters g. 9, placed in pendulous frames. so that they
can be presented to the periphery of a drill at any desired angle, substantially
as shown.
6thly, the hollow cone pulleys and the arrangement of gearing, by means
of which motion is transmitted from them to the cutters g, substantially as
described.
7thly, face cutters, such as that shown in Figures 14 and 15, in combination
with the mandrils of the cherry cutters, substantially as described.
In witness whereof. I, the said William Clark, have hereunto set my hand
and seal, this Twenty-third day of October, in the year of our Lord
Ang thousand sight hundred and sixty-six.
5
Witness.
JAMES DAISH,
53, Chancery Lane.
Loudon.
W. CLARK. (L.D.)