Improvements in Twist Drill Grinding Machines.
Year: 1889

page_text: Date of Application, 23rd Sept., 1889
Complete Specification Left, 21st June, 1890-Accepted, 26th July, 1890
PROVISIONAL SPECIFICATION.
Improvements in Twist Drill Grinding Machines.
A communication from abroad by MILNER PRINCE HIGGINS and CHARLES HILL
MORGAN, both of Worcester, in the state of Massachusetts, one of the United
States of America, Mechanical Engineers.
I, ALFRED GEORGE BROOKES of the firm of Wm.. Brookes & Son, of 55 & 56
Chancery Lane in the County of Middlesex, Patent Agent do liereby declare the
nature, of this invention to be as follows:-
This invention relates to twist drill grinding machines, the object being to produce
an improved form of grinding for the end surface of each drill lip. It has been
particularly the object in the invention herein described, to produce a device that does
not necessitate the chucking and centering of the drills, the operation of the saine
being obvious to ordinary unskilled workmen, and the adjustment for each size of
drill being plainly indicated on the machine.
To this end, this invention consists of several novel and valuable features of
construction, and especially of an improved drill holding and operating device
hereinafter more fully described. This device is so arranged that the drills are
held in place, during 'the grinding operation by their own gravity aided by the hand
of the operator, thus effecting a saving of the time usually spent in adjusting the
saine in a chuck. This drill holding and operating device consists of a rigid and a
movable Vgrooved drill support, a reversible drill stop, an improved lip rest
permanently set and adjusted, for all sizes of drills, and an angular graduated slide so
constructed as to perform the triple duty of giving the drill two adjustinents, and
feeding the same against the grinding wheel by means of the same feed screw.
The device consists further of a threaded axis of oscillation upon which the
correspondingly threaded drill holder swings or oscillates helically, and gives the
drill lip a screw thread surface or helicoid. The advantages of this shape of drill lip
may be briefly enumerated as follows. If the movement of any point on the surface
of a drill lip be followed as the drill is fed to its work with a regular feed advance-
ment, it will be found that the said point will describe a helix of greater or less
pitch, according as the feed is accelerated or retarded, and if the drill be stopped in
the midst of its cutting, the shape found at the bottom of the hole will be helicoidal
instead of a conical surface, and it follows that a drill lip ground to a helicoidal
surface will be best adapted for cutting under such conditions. Other devices have
been tried heretofore that produce surfaces of various shapes, including right
cylinders and cones, and various warped surfaces, and machines also that make a
surface approximating a helicoid by means of cams and like devices. The last
named class of machines, however, employ an axis that is coincident with the axis of
the drill, and the resultant surface leaves the drill point rounded on too small a radius,
and the cutting properties of the end of the drill web or point are in a measure
destroyed. The central web of a twist drill is made with a thickness proportionate
to the diaineter of the drill, and is necessary to give strength and stiffness to the
same, but it forms a point of great resistance to the drill in cutting, and should be
shaped in the best form to make its scraping action as free as possible. In this
invention it is aimed to grind this point on as long a radius as practicable and
obtain best results.
If a drill lip be ground on an axis that coincides with the axis of the drill, and any
circular element on this lip surface (as, for instance, an element midway between the
periphery and point on a drill of one inch radius) be taken, the radius of this element
of surface will be one half the radius of the drill or will coincide with the radius of
the drill at this point. If, however, the axis of the ground surface be conceived as

page_text: inclined to the axis of the drill, it is evident that the curvature of the lip at the
periphery may be the same as in the first case, while the radius of curvature near the
drill point may be much greater than it was in the first case, and consequently a
drill point is produced more uearly approximating a straight line, and a clearer
cutting point is produced. I therefore employ an axis of oscillation considerably
removed from and inclined to the axis of the drill, and produce a drill lip surface of
proportionately longer radius at the point than at the periphery of the drill, and a
helicoidal surfice.
The
Supported on the main standard of the machine is the annular grinding wheel,
which is held in place on its taper spindle by an internally threaded washer.
spindle pulley is held by a feather key on the taper spindle. In the outer end of this
pulley is screwed a bushing abutting against the end of the taper spindle and held by
central screw. By unscrewing this bushing slightly, and tightening screw, the
pulley is forced farther on to the spindle and adjustments thus made for wear.
oil channels serve to convey the waste oil from each end of the spindle to the hollow
in the center of the standard, where it may be conveyed to a drip cup. The main
standard is bored and fitted with a clamping screw operated by a suitable handle to
bind the cylindrical slide in any desired position. On one end of the slide is mounted
a swivel head held by a central bolt screwed tightly into the same, and maintaining
the proper tension. The swivel head is provided with an aperture forming an
inclined sleeve, which is internally threaded for the reception of a similarly threaded
shaft, which is fastened in a guide bracket by a set screw, and turning with the guide
bracket moves itself and the bracket along, according to the pitch of the screw.
On this guide bracket is mounted the drill holder and its attendant parts. The object
of the swivel head is to allow the drill bolder to be moved across the grinding wheel,
parallel to the grinding surface, to distribute the wear and maintain the truth of the
wheel. The cylindrical slide may be made to perform the functions of the swivel
head, by slightly loosening the clamping screw and permitting the cylindrical slide to
rotate. The drill holder is provided at the bottom with angular slide working on
dovetailed ways, on the guide bracket and operated by ineans of the hand wheel and
feed screw.
Graduations upon the guide bracket indicate the proper position of the
slide by the pointer for the different sized drills. The drill holder is provided with a
planed guide way at one end of the rigid V-shaped support for the drills, and
adjustably mounted on the said guide way is the sliding V-shaped support held by a
set screw which is operated by a lever, and also there is likewise mounted the sliding
drill stop which is reversible, and may be clamped in any position by a screw, this
the stationary lip rest, held in place by screws is the line of drill contact, and may
be inclined to the bisecting line of the V-angle, and intersecting. the same near the
apex of said angle, the object being to compensate for the variation in thickness of
the drill points. By this means, the cutting edges of all drill lips placed against
the rest are held parallel to each other.
To grind a drill with this device, the clamping screw is loosened, and the
cylindrical slide is pulled out and clamped so that the drill holder is some distance
away from the grinding wheel, and a drill is then, laid in the V-shaped supports.
The movable support and drill stop being suitably adjusted, for the purpose, and the
lip of the drill to be ground being placed in contact with the lip rest, and extending
about an eighth of an inch beyond it. The drill holder is then moved by means of
the feed screw and hand wheel until the pointer indicates on the guide bracket the
graduation, that corresponds to the diameter of the drill being ground. The drill is
now held in place. by one hand, while the cylindrical slide is moved until the drill
comes in light contact with the grinding wheel. The cylindrical slide is then
clamped rigidly in place, and with one hand holding the drill, the other operates the
feed screw, by means of the hand wheel, and at the same time oscillates the drill, and
holder until the guide bracket. comes in contact with the stops on either side. The
drill may be repeatedly reversed in the drill holder with one hand until both lips be
ground exactly alike. Clearance. is obtained on drills ground with this invention, by
ineans of the, threaded axis which advances the drill as it is being ground, and a

page_text: variation of clearance necessary for varying diameters of drills is obtained by means
of the angular slide on the drill holder before mentioned, which carries the drills
forward, and away from the axis of oscillation, in regular proportion to their
diameters, giving varying radii of grinding and varying lateral adjustment for the
different degrees of clearance required.
I have described an angular slide moving in a direction oblique to the action of
the drill, thus giving the drill a longitudinal and lateral adjustment with but one
movement of the slide. The lateral adjustment of the drill, however, may be obtained
in another manner, as follows. In placing a drill in the grooved V-shaped drill
holder, the center of each succeeding drill of larger diameter will rest higher up in
the drill holder, which is obvious, and it is also evident that the centers of all drills
will lie in the right line which bisects the angle of the V. If the V-holder he
inclined away from the axis of oscillation in a lateral direction, this bisecting line will
also be inclined away from the same, and as the drill centers always lie in the bisecting
line of the V, they will have an increased Interal adjustment from the axis of
oscillation proportionate to their increased diameters, a result precisely similar to that
obtained by means of the angularity of the slide previously described, the slide in
this case maintaining the axes of the drills in the same vertical plane.
I do not, therefore, confine myself to an angular slide to obtain proportionate
lateral adjustment for different sized drills.
Dated the 23rd day of Sentember 1889
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agenis.
COMPLETE SPECIFICATION.
Improvements in Twist Drill Grinding Machines.
A communication from abroad by MILNER PRINCE HIGGINS and CHARLES HILL MORGAN,
both of Worcester, in the State of Massachusetts, one of the United States of
America, Mechanical Engineers.
I, ALFRED GEORGE BROOKES of the firm of Wm. Brookes & Son, of 55 & 56
Chancery Lane in the County of Middlesex Palent Agent do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularis described and ascertained in and by the following statement:-
This invention relates to Twist Drill Grinding Machines, the object being to produce
an improved form of grinding for the end surface of each drill lip It has been
particularly the object, in the invention herein described, to produce a device that.
does not necessitate the chucking and centering of the drills, the operation of the
same being obvious to ordinary unskilled workmen, and the adjustment for each size
of drill being plainly indiented on the machine.
To this end, this invention consists of several novel and valuable features of con-
struction, and especially of an improved drill holding and operating device hereinafter
more fully described. This device is so arranged that the drills are held in place,
during the grinding operation, by their own gravity aided by the hand of the operator,
tbus effecting a saving of the time usually spent in adjusting the same in a chuck.
This drill bolding and operating device consists of a rigid and moveable V grooved
drill support, a reversible drill stop, an improved lip rest permanently set and adjusted,
for all sizes of drills, and an angular graduated slide so constructed as to perform
the triple duty of giving the drill two adjustments, and feeding the same against the
grinding wheel by means of the same feed screw.
The device consists further, of a threaded axis of oscillation upon which the
correspondingly threaded drill holder swings or oscillates helically, and gives the drill
lip a screw thread surface or helicoid. The advantages of this shape of drill lip may
he briefly enumerated as follows. If the movement of any point on the surface of a
drill lip be followed as the drill is fed to its work with a regular feed advancement,
it will be found that the said point will describe a helix of greater or less pitch,

page_text: according as the feed is accelerated or retarded, and if the drill be stopped in the
midst of its cutting, the shape found at the bottom of the hole will be helicoidal
instead of a conical surface, and it follows that a drill lip ground to a helicoidal
surface will be best adapted for cutting under such conditions.
Other devices have been tried heretofore that produce surfaces of various shapes,
including right cylinders and cones, and various warped surfaces, and machines also,
that make à surface approximating, a helicoid by means of cams and like devices.
The last named class of machines, bowever, employ an axis that is coincident with
the axis of the drill, and the resultant surface leaves the drill point rounded on too
sinal a radius, and the cutting properties of the end of the drill web or point are in
a measure destroyed. The central web of a twist drill is made with a thickness pro-
portionate to the diameter of the drill, and is necessary to give strength and stiffness
to the same, but it forms a point of great resistance to the drill in cutting, and should
be shaped in the best form to make its scraping action as free as possible. In this
invention, it is aimed to grind this point on as long a radius as practicable and obtain
best results.
If a drill lip be ground on an axis that coincides with the axis of the drill, and
any circular element on this lip surface (as, for instance, an element midway between the
periphery and point on a drill of one inch radius) be taken, the radius of this element
of surface will be one half the radius of the drill or will coincide with the radius of
the drill at this point. If, however, the axis of the ground surface be conceived as
inclined to the axis of the drill, it is evident that the curvature of the lip at the
periphery may be the same as in the first case, while the radius of curvature near the
drill point may be much greater than it was in the first case, and consequently a drill
point is produced more nearly approximating a straight line, and a clearer cutting
point is produced..
I therefore employ an axis of oscillation considerably removed from, and inclined
to the axis of the drill, and produce a drill lip surface of proportionately longer radius
at the point than at the periphery of the drill, and a helicoidal surface. In the
accompanying drawings, the same letters indicating like parts of each-
Fig. 1 is a side elevation of the twist drill grinding machine, shown partly in
section.
Fig. 2 is a side elevation of the drill holding and operating device, and the
grinding wheel.
Fig. 3 is an end elevation of the swivel-head F, and shows, handle F1, and the
projections which serve as stops for the oscillating drill holder.
Fig. 4 is an end elevation of the V shaped drill holder showing drill in place.
Fig. 5 is an end elevation of the main supporting standard with the drill
operating mechanism removed and the grinding wheel in place.
Fig. 6 :—is a plan view of the drill holder at a right angle to the top surface of the
same.
Fig. 7 is an enlarged end elevation of drill holder, shewing different sized drills
in place and the lip rest.
Fig. 8 is an elevation of a twist drill, illustrating the peculiarities of the improved
surface for cutting lips.
A is the main standard of the machine, and D the annular grinding wheel which
is held in place on the taper spindle B by the internally threaded washer L. C is
the pulley, and is held by a feather key not shown: In the outer end of the pulley C
is screwed bushing abutting against the end of the spindle B. and held by central
screw d. By unscrewing bushing a slightly, and tightening screw d, the pulley C is
forced farther on to the spindle B and adjustments thus made for wear. The oil
channels serve to convey the waste oil from each end of the spindle to the hollow in
the centre of the standard, where it may be conveyed to a drip cup.
The standard A is bored and fitted with a clamping screw operated by the handle K
to bind the cylindrical slide E in any desired position. On one end of the slide
is mounted the swivel head F, held by the central bolt E, screwed tightly into the
same, and maintaining the proper tension. The swivel head F is provided with an

page_text: aperture forming an inclined sleeve, which is internally threaded for the reception of
the similarly threaded shaft G1, which is fastened in the guide bracket G by a set
screw, h, and turning with the bracket. G moves itself and the bracket along the
line db, according to the pitch of the screw. On this guide bracket G is mounted
the drill holder H and its attendant parts. The object of the swivel head is to
allow the drill holder to be moved across the grinding wheel, parallel to the grinding
surface, to distribute the wear and maintain the truth of the wheel. The cylindrical
slide. E may be made to perform the functions of the swivel head F, by slightly
loosening the clamping screw K, and permitting the cylindrical slide to rotate.
The drill holder H is provided at the bottom with angular slide working on dove-
tailed ways, on guide bracket G, and operated by means of the hand wheel and
feed screw I. Graduations upon bracket G indicate the proper position of the slide by
the pointer m for the different sized drills. The drill holder H is provided with a
planed guide way, at one end of which is a rigid V shaped support for the drills, and
adjustably mounted on the said guide way is the sliding V shaped support I, held by
a set screw o' which is operated by a lever, and also there is likewise mounted the
sliding drill stop J, which is reversible, and may be clamped in any position by the
screw o; t is the stationary lip rest, held in place by screws t¹;, n¹ is the line of
drill contact, and is shown inclined to the bisecting line of the V angle, and inter-
secting the same near the apex of said angle, the object being to compensate for the
variation in thickness of the drill points.
By this means the cutting edges of all drill lips placed against the rest are heldi
parallel to each other.
The points numbered 1, 2, 3, 4, 5, in Fig. 6, show, somewhat exaggerated, the
different positions of drills of large diameter, in reference to the axis of oscillation,
which is fixed at the point al.
In Fig. 8 the line c d is a somewhat magnified representation of the helix
described by a single point on a drill lip revolving with a regular feed advancement,
&aba line on the periphery of a drill lip ground to a helicoidal surface, and shows
a portion of a helix of greater pitch and longer radius than c, d, but conforming to
it in a certain degree, or as much as is consistent with a good cutting drill point, and
the proper clearance.
To grind a drill with my device, the clamping screw K is loosened, and the
cylindrical slide E is pulled out and clamped so that the drill holder is some distance
away from the grinding wheel, and a drill is then laid in the V shaped supports. The
movable support I and drill stop J being suitably adjusted, for the purpose, and the
lip of the drill to be ground being placed in contact with the lip rest t, and extending
about an eighth of an inch beyond it. The drill holder is then moved by means of
the feed screw I and hand wheel k until the pointer. indicates on the guide bracket G
the graduation that corresponds to the diameter of the drill being ground. The
drill is now held in place by one hand, while the cylindrical slide E is moved until
the drill comes in light contact with the grinding wheel. The cylindrical slide is
then clamped rigidly in place, and with one hand holding the drill, the other operates
the feed screw 1, by means of the hand wheel k, and at the same time oscillates. the
drill and holder until the guide bracket comes in contact with the stops p on either
side.
The drill may be repeatedly reversed in the drill holder with one hand until both
lips be ground exactly alike. Clearance is obtained on drills ground with my inven-
tion, by means of the threaded axis which advances the drill as it is being ground,
and a variation of clearance necessary for varying diameters of drills is obtained by
means of the angular slide on the drill holder H before mentioned, which carries
the drills forward, and away from the axis of oscillation, in regular proportion to
their diameters, giving varying radii of grinding and varying lateral adjustment for
the different degrees of clearance required, as clearly shown in Fig. 6.
In Figs: 1 & 2, the different radii of grinding on drills S and S' is shown. The
line a, b is the axis of oscillation. The points 1, 2, 3, 4, & 5, indicate different
positions of the drill points, and the parallel lines drawn to each of these points

page_text: respectively represents centre lines of drills in each position, as the drill holder is
carried out in the direction e¹, f¹ by the feed screw I.
In the foregoing specification, I have described an angular slide moving in a
direction oblique to the axis of the drill, thus giving the drill a longitudinal and
lateral adjustment with but one movement of the slide. The lateral adjustment of
the drill, however, may be obtained in another manner with my device, as follows,
In placing a drill in the grooved V shaped drill holder, the centre of each succeeding
drill of larger diameter will rest higher up in the drill holder, which is obvious, and
it is also evident that the centres of all drills will lie in the right line which bisects
the angle of the V. If the V holder be inclined away from the axis of oscillation in
a lateral direction, this bisecting line will also be inclined away from the same, and
as the drill centres always lie in the bisecting line of the V, they will have an
increased lateral adjustment from the axis of oscillation proportionate to their increased
diameters, a result precisely similar to that obtained by means of the angularity of
the slide previously described, the slide in this case maintaining the axes of the drills
in the same vertical plane.
Having now particularly described and ascertained the nature of the said inven-
tion of Improvements in Twist Drill Grinding Machines" and in what manner
the same is to be performed I declare that I do not confine myself to an annular
slide to obtain proportionate lateral adjustment for different sized drills, but that
what I do claim, is :—
First. The V grooved drill holder (H) in combination with the stationary drill lip
rest (4), which has its line of drill contact inclined to the bisecting line of the V angle,
and intersecting the same near the apex of said angle, as and for the purpose
described.
Second. The combination with the drill holder (H) and guide bracket (G) of an
inclined and screw-threaded axis of oscillation along which the drill holder is helically
advanced by said screw-thread oscillated as above set forth.
Third. In combination with the V grooved drill holder, (H) the separate drill
stop, (J), and the independent V shaped support, (I), which is adjustable in a
direction parallel to the axis of the drill, as described..
Fourth. The combination of the drill holding mechanism comprising drill holder (H),
guide bracket, (G), separate drill stop, (J), and the independent adjustable V shaped
support (1), with the cylindrical slide, (E), constructed and operated as and for the
purpose set forth.
Fifth. The combination of the drill holding mechanism above described, supported
on a cylindrical slide provided with a swivel arranged to swing the drill to any
desired part of the grinding surface as described.
Sixth. The drill holder, (H) the stationery lip rest, (t) and the guide bracket, (G)
combined with the inclined and screw-threaded axis of oscillation (G) arranged to
helically advance the drill along the axis toward the grinding wheel as the drill
holder is oscillated as described.
Seventh. The angular sliding drill holder, (H) and guide bracket, (G) combined
with the swivel head, (F) arranged to swing the drill across the grinding surface in
a plane parallel to the same, ns and for the purpose described.
Dated the 21st doy of L 1900
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for the Applicant.