Improvements in Machinery for Forming, Grinding, and Sharpening the Cutting Edges of Boring-bits, Drills, Reamers, and similar Cutting Tools.
Year: 1886

page_text: Date of Application, 20th Nov., 1886.
Complete Left, 23rd July, 1887
Complete Accepted, 11th Oct., 1887.
Improvements in Machinery for Forming, Grinding, and Sharpening
the Cutting Edges of Boring-bits, Drills, Reamers, and similar
Cutting Tools.
I GRAY DENISON EDMESTON of 29 Johnson Street, Cheetham, in the City of
Manchester, Engineer, do hereby declare the nature of the said invention, to be
as follows:-
The object of my invention is a machine in and by which the cutting edges of
Boring-bits Drills, Reamers and other similar cutting tools may be formed, ground
and sharpened and consists in a combination and arrangement or in combinations
and arrangements of mechanism with a grinding wheel, by which the several cutting
edges or facets of the said tools are or may be held to be operated upon by the
grinding wheel or surface in such manner as to produce cutting edges having the
requisite form, contour or backing off" and which are symmetrically true with
the axes of the said tools.
.
66
The combinations and arrangements of mechanism above referred to are as follows.
A chuck, capable of rotating and moving in the direction of its longitudinal axis,
in which one end of the stem or shank of the cutting tool to be operated upon, is
centred and gripped or held and by which chuck the tool can be rotated or partly
rotated upon its longitudinal axis and moved to and from the grinding wheel or
surface.
The said chuck is mounted upon an arm provided with longitudinal and transverse
adjustments in order to be able to present and adjust either the flank or nose of the
cutting tool to the grinding surface.
The said arm having the said chuck is mounted upon a plate or table, carrying a
flat rest for supporting that end of the tool to be ground which plate or table is
arranged to be rotated or partly rotated or oscillated (say 90 degrees) upon a
vertical axis to hold the tool to be operated upon to the grinding surface at the
required angle.
.
The said plate or table movable on a vertical axis with the parts carried by it is
mounted upon a transverse slide provided on its upper side with a circular seating,
and an axial pin which forms the centre of oscillation for the said plate or table. and

page_text: the lower surface of the said slide can move freely upon a bed or slideway which is
parallel to the grinding face of the wheel-the said bed or slideway has also its
own transverse adjustment in order that it may be placed and secured at any required
distance from the face of the grinding wheel.
One important feature of my invention when that edge of a grinding wheel is
used which is parallel to its axis of rotation (which I prefer) is to arrange so
that the plane of the axis of the tool to be operated upon, will not be in the
sanie plane as the axis of the grinding wheel but at such distance above the
plane of the latter as will cause the wheel to grind to an angle giving the required
clearance or "backing off" to the cutting edge, where the cutting edge requires
such clearance or backing off.
For grinding or sharpening what are termed twist drills I combine with the
mechanism herein before described a V rest in place of the flat rest hereinbefore
mentioned, which V rest is adjustable and is secured in a suitable socket formed
on the said plate or table that can be oscillated on a vertical axis.
In this rest the drill when being ground can be rotated or partly rotated when
presented to the grinding surface at the required angle by the mechanism above
referred to.
For grinding or sharpening tools such as tapering, boring-bits, reamers and like
tools to be held in centres at both ends while being operated upon, I combine with
the mechanism above described a bracket carrying a centre which is attached to the
forward end of the said arm carrying the said chuck and when using which centering
bracket the said flat rest is removed.
I prefer to use in combination with the mechanism hereinbefore described a
grinding wheel commonly known as an emery grinding wheel and that face of such
emery wheels which is parallel to the axis of rotation through the disc face which is
at a right angle to the axes if rotation may be used and ordinary grinding stones may
also be used in place of emery wheels.
If desired the axis of the Emery wheel or grinding stone may be in bearings
carried on slides so as to be adjustable to and fro or up and down or at any desired
angle in relation to the edge of the tool to be operated upon.
Dated this Nineteenth day of November 1886.

page_text: COMPLETE SPECIFICATION.
Improvements in Machinery for Forming, Grinding, and Sharpening
the Cutting Edges of Boring-bits, Drills, Reamers, and similar
Cutting Tools.
I GRAY DENISON EDMESTON of 29 Johnson Street Cheetham, in the City of
Manchester, 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:—
The object of my invention is a machine in and by which the cutting edges of
Boring-bits, Drills Reamers and other similar cutting tools may be formed, ground
and sharpened, and consists in a combination and arrangement or in combinations and
arrangements of mechanism with a grinding wheel by which the said tools are or may
be held so that their several cutting edges or facets are or may be operated upon by
the grinding wheel or surface in such manner as to produce cutting edges having
the requisite form contour or "backing off" and which are symmetrically true with the
axes of the said tools.
The combinations and arrangements of mechanism above referred to are as follows.
A chuck capable of rotating and moving in the direction of its longitudinal axis,
in which one end of the stem or shank of the cutting tool to be operated upon is
centred, and gripped or held and by which chuck the tool can be rotated or partly
rotated upon its longitudinal axis and moved to and from the grinding wheel or
surface.
The said chuck is mounted upon an arm provided with longitudinal and transverse
adjustments in order to be able to present and adjust either the flank or nose of the
cutting tool to the grinding surface.
The said arm having the said chuck is mounted upon a plate or table, carrying a
flat rest for supporting that end of the tool to be ground which plate or table is
arranged to be rotated or partly rotated or oscillated (say 90 degrees) upon a vertical
axis to hold the tool to be operated upon to the grinding surface at the required angle.
The said plate or table movable on a vertical axis with the parts carried by it is
mounted upon a transverse slide provided on its upper side with a circular seating,
and an axial pin, which forms the centre of oscillation for the said plate or table, and
the lower surface of the said slide can move freely upon a bed or slideway which is
parallel to the grinding face of the wheel the said bed or slideway has also its own
transverse adjustment in order that it may be placed and secured at any required
distance from the face of the grinding wheel.
One important feature of my invention when that edge of a grinding wheel is used
which is parallel to its axis of rotation (which I prefer) is to arrange so that the plane
of the axis of the tool to be operated upon will not be in the same plane as the axis of
the grinding wheel but at such distance above the plane of the latter as will cause
the wheel to grind to an angle giving the required clearance or "backing off" to the
cutting edge, where the cutting edge requires such clearance or backing off.

page_text: For grinding or sharpening what are termed twist drills I combine with the
mechanism herein before described a V rest in place of the flat rest hereinbefore
mentioned which V rest is adjustable and is secured in a suitable socket formed on
the forward end of the said arm carrying the said chuck.
In this rest the drill when being ground can be rotated or partly rotated when
presented to the grinding surface at the required angle by the mechanism above
referred to.
For grinding or sharpening tools such as tapering boring-bits, reamers and like
tools to be held in centres at both ends while being operated upon, I combine with
the mechanism above described a bracket carrying a centre which is attached to the
forward end of the said arm carrying the said chuck and when using which centering
bracket the said flat rest is removed."
I prefer to use in combination with the mechanism herein before described a grinding
wheel commonly known as an emery grinding wheel and that face of such emery
wheel' which is parallel to the axis of rotation though the disc face which is at a right
angle to the axes if rotation may be used and ordinary grinding stones may also be
used in place of emery wheels.
If desired the axis of the Einery wheel or grinding stone may be in bearings
carried on slides so as to be adjustable to and fro or up and down or at any desired
angle in relation to the edge of the tool to be operated upon.
In the accompanying drawings which form part of this Specification, Fig. 1 is a
side elevation, and fig. 2 is a plan of my machine as arranged for grinding what are
known as Flat drills or boring bits, fig. 3 is a longitudinal section, and fig. 4 an end
view in detail of the gripping or holding chuck.
Fig. 5 is a plan of part of my machine when arranged, for grinding taper flat
drills.
Fig. 6 is a plan of part of my machine when arranged for grinding twist drills, and
fig. 7 is an end view of detail showing the method of fixing and adjusting the V rest
to the arm when used for twist drill grinding.
In all the several figures the same letters of reference are used to indicate the same
parts when repeated in the different figures.
Referring to figs. 1 and 2, a is a standard or pedestal of box form which carries the
whole of the mechanism forming the machine, the upper portion of which is made to
act as a water or sludge box, and is provided with a plug a' for the purpose of cleaning
out, and a swivelling pipe a² which may be turned down in order to draw off the
surface water.
Upon the top flanges of the standard a are fixed two small plummer blocks 616²,
which carry the spindle of the grinding wheel b and the splash guard & the holes in
the flanges for securing the latter being slotted to allow for horizontal adjustment
as the wheel b is reduced in diameter by wear, the top of the splash guard 63 is also
fitted with a table for receiving the water can used to supply the grinding wheel
with water.
The back of the standard a is provided with. two brackets or snugs a³, a for
carrying the counter shaft c and also two brackets ab, as for receiving the sliding belt
guide c¹. The front of the standard a is provided with a vertical seating having T
headed slots for receiving the angle bracket d upon which the principal portion of the
apparatus is mounted, and the angle bracket d is capable of a vertical adjustment by,
means of the capstan headed screw d¹ and can be bolted securely at any required!
elevation by the two bolts d², d³.
The object of this adjustment is to present the tool to be ground, with its axis at
such an elevation above the axis of the grinding wheel b that a tangent with its
circumference at the point of contact shall form such an angle with the axis of the
tool, as shall be necessary to give the requisite keenness to or clearance behind
the cutting edge of the said tool and may be about 100 degrees of the circle from the
horizontal or 10 degrees from the perpendicular.
The countershafte is provided at one end with a pair of fast and loose pullies c³, c³
for receiving motion from a first motion driving pulley, and, at the other end is

page_text: fitted with a driving pulley for giving motion to the spindle 6 of the grinding
wheel b through the small pulley 65 fitted upon the end of the spindle 6*.
The angle bracket d. (fig. 1) is planed upon its upper horizontal surface to receive a
small bed or sliding way e the V slides of which are shown by dotted lines in
fig. 1, and this bed e is so fitted to the angle bracket d, that the V sliding way is
always parallel with the axis of the grinding wheel b but may be moved to or from
and fixed by the bolt el at any required distance from the face of the wheel b.
Upon this bed or sliding-way e is fitted a transverse slide the lower surface of
which is made to slide freely and truly upon the bed or sliding way e and is moved
to and fro in a direction always parallel with the axis of the grinding wheel b by
means of the traversing screw f and handle.
Upon the upper surface of this traversing slide is formed a circular or segmental
seating made to receive the horizontal quadrant plate or table g and a vertical or
axial pin g', which is truly in the centre of the circular seating, gives additional
security that the quadrant plate, or table g shall be capable of being rotated truly
around a fixed centre in a horizontal plane, through any required angle.
The quadrant plate 9 is further provided with a lower segmental projecting
flange, which is covered by a segmental or quadrant strip f* secured to the
transverse slide f, and which further retains the quadrant plate upon the seating
provided for it upon the transverse slide f.
The outer circumference of the quadrant plate has cast upon it a projecting
snug g³ shown by dotted lines on Figs. 2, 5 and 7 and is placed so as to clear the
upper surface of the quadrant strip and is formed to act as a stop, to determine
the angle through which the quadrant plate g may be moved by being brought on the
one side against the screwed adjustable stop for on the other side, against the pin
stop for which latter, a series of holes are provided upon the circumference of a
flange formed on the upper side of the quadrant strip.
Upon the opposite side of the quadrant plate g a vertical flange g is provided to
receive a rest g³ secured to it by two bolts g g².`
The upper surface or table of the quadrant plate g is formed with two T grooved
slots 98, 9, to receive and retain the arm h, upon the lower face of this arm h are two
projecting tongues which truly fit into the grooved slots go, go, so that it may be
capable of a transverse adjustment by means of the cross traversing screw h¹ and
hand wheel h³.
The prolonged portion of this arm h may be made of any required length, suitable
to the length of the drills to be operated upon, and on one side of it there is a
longitudinal grooved slot ³ for receiving a vertical side bracket i which may be
bolted to the arin at any required distance from the ond.
Upon the top of the arm h there is cast a projection * made to receive a capstan
headed centring screw the use of which will be, further explained in describing the
action of the machine.
The vertical side bracket i has a seating formed to receive the gripping or holding
chuck k which is bolted to the side bracket, by the bolt k¹ and is capable of a limited
longitudinal adjustment by means of the screw and hand wheel.
The details of the gripping or holding chuck k will be more clearly understood by
reference to Figs. 3 and 4 where k is a socket, bored to receive a rotating sleeve k²
and formed with a collar, or enlargement at one end on the outer circumference of
which are drilled a series of holes at equal distances, in the positions shown by the
dotted lines in Fig. 4: this sleeve is provided with an arm k fitted with a spring
plug and finger bit e, so that the plug or pin may be withdrawn and the sleeve
rotated upon its axis, and fixed in any position by the plug or pin k³ entering the
holes in k³.
This sleeve is bored out to receive a stock which slides freely into it, and the
outside of which has recesses formed to receive two steel grippers k, k³ for taking
hold of the stem of the drill, each of which is formed with a hook at one end, passing
into a groove formed in the stock, and the opposite ends bent at right angles, meeting
towards each other and formed with chisel edges. A bolt passes through both of

page_text: these grippers, and by its action, the grippers may be drawn together until they take a
firm bite upon the stem of any drill placed between them; a small steel spring hoop j
is inserted between the grippers to distend them, when the bolt j is unscrewed and
the drill stem released. The stock k' is also fitted with a steel centre which has an
elongated slot to allow the bolt j to pass freely through it and permit of a limited
longitudinal adjustment which is effected by the handle screw and the hand wheel
and by this means the point of the centre may be forced into the centre hole which
is usually formed in the end of all drill stems, by this means the end of the drill stem
is retained centrally true with the stock k'. Upon the end of the stock k' there is
also formed an abutting flange having two holes and diametrically opposite to
each other, and a pin in the hole is fitted into the end of the sleeve k so that the
stock may be partially withdrawn a sufficient distance to clear the pin in the hole j
rotated halfway round upon its axis, and again pressed forward against the abutting
flange.
At the front end of the stock ka hole is drilled transversly to its axis, for the
insertion of a pin 7 (see fig. 2) which retains the stock k in its position, preventing
its being withdrawn or forced back, and which I find to be useful when fixing drills
in the grippers, and necessary, when the machine is used as shown in Fig. 5.
Having now described the details of the parts of my machine as shown by Figs. 1
to 4, and which illustrates the whole of the combination used for the purpose of
grinding flat drills or boring-bits, I now proceed to describe the method of working
the machine, when operating upon the last named tools, as by so doing I shall facilitate
the explanation of the machine when used for the purposes illustrated by Figs. 5,
6 and 7.
The width or diameter of the stem of the drill is first ascertained, and the centring
screw hadjusted until the distance of the inner side of the capstan head, from the
projecting piece * equals half the diameter or width of the stem; the cutting end or
nose of the drill is then placed upon the rest g³ and the side bracket i moved until the
centre point of the centre ³ enters the centrehole formed in the end of the drill stem,
with the nose of the drill in a line with the front side of the rest and the side
bracket is securely bolted to the arm h in that position; the bolt j is now screwed
down until the grippers k³, take a firm bite upon the end of the stem, and during
this operation the advanced portion of the stem must be held in contact with the
point of the adjusting or centring screw ; the handle screw ³ may now be slightly
tightened to ensure that the centrepoint of the centre is well home in the centrehole,
and the drill is now fixed ready for grinding operations with the axis of its stem truly
in line with the axis of the gripping chuck.
It is necessary here to explain that the centring screw is made of such length
that when the capstan head abuts against the projecting bracket / the point will be
truly in line with the centre or axis of the gripping chuck k so that by adjusting
the screw until the distance of the inner side of the head from the projecting
bracket is equal to half the diameter of the stem of the drill the point of the
screw will have receeded from the axial line of the chuck an equal distance, and by
securing the drill with its stem in contact with the point of the screw, the axis of the
stem of the drill will coincide horizontally with the axis of the gripping chuck.
The grinding wheel 6 may now be set in motion, and by turning the arm h in the
direction of the stop screw the arm and its attached quadrant plate g will rotate
upon the axis g until the stop piece 93 comes into contact with the point of the
screw in which position the flank or side of the drill will be parallel with the face
of the grinding wheel band by turning the screw h¹ will be brought into contact with
it, then by turning the screw fl the flank or side of the drill will be traversed across
the face of the grinding wheel and a true cutting edge will be formed. To perform
the same operation upon the opposite flank the arm his first moved a short distance
to withdraw the stop piece 9³ from contact with the screw stop f which will at the
same time remove the flank of the drill from contact with the grinding wheel, then
by taking out the pin, the stock k may be partially withdrawn from the sleeve k²
until the end of the drill is clear of the rest go, and it can then be rotated a half

page_text: revolution, returned into the sleeve k² the pin in the hole entering the hole in the
abutting flange of the stock, then by returning the arm h until the stop piece 9°
rests against the screw stops, and traversing the slide f by the screw f₁ as before
explained the second flank or side of the drill will be ground equally true with the
first, the cutting edge being formed at exactly the same distance from the axis of the
stem, care being taken in both cases, that the drill stem is held in contact with
the point of the centering screw 5, it will also be understood, that by adjusting the
stop screw the flanks or sides of the drill may be formed either parallel to or
slightly tapering in relation to the axis of the drill stem, and that by adjusting
the screw the drill may be ground to suit any diameter with perfect accuracy.
To grind the cutting nose of the drill, the stop pin fe is inserted into one of
the several holes made in the flange f corresponding to the angle to which it is
determined to grind it, and the arm h moved in that direction, until the stop
piece g³ is in contact with the stop pin fe, then by turning the screw i¹ the nose of
the drill will be brought into contact with the grinding wheel, and traversed across
its face by the screw fl as in the previous operation; the pin is then taken out, the
stock rotated a half revolution as before, and by pressing it home against the
abutting flange the opposite cutting edge of the nose will be ground to the same
angle, and the same length, in relation to the axis of the stem, as the one just
operated upon.
If while in this position the arm his moved gently round, until the stop-piece 9³
comes again into contact with the screw stopf, the angles formed by the nose with the
flanks of the drill, may be rounded off to the arc of a circle of which the axial pin g¹
forms the centre and the radius of this are, may be made greater or less, according to
the position in which the bed or sliding way e is fixed upon the angle bracket d if
the bed e is fixed further from the face of the grinding wheel 6 the radius of the arc
will be greater, and if fixed nearer the radius of the arc will be less, or nil, according
to the position in which it is fixed.
For grinding drills having round stems, such as are used in drilling machines, the
operations are the same as for flat drills or boring bits, the V d recesses in the ends
of the grippers kk, being formed for the purpose of taking hold of the round stem
or shank of such drills.
And it will also be evident that boring bits, or drills having tapering flanks, such
as are used for boring taper holes of short depth may be ground in the same way as
ordinary boring bits by adjusting the screw stop f so as to grind to the required
taper; but for grinding boring bits having tapering sides or flanks of moderate length,
I prefer to use the modification illustrated by Fig. 5 which shows the addition of a
centring bracket to be attached to the forward end of the arm to be used for
supporting the cutting ends of taper boring bits reamers, or such other tools,
as it is desirable to support in centres during the operation of grinding or
sharpening.
In this arrangement, the rest 96 (Figs. 1 and 2) is removed, and the centring
bracket is attached to the projection of the arm h and which is bored to receive a
stem formed on the bracket and shown by dotted lines on Fig. 5, while the lower
portion of the centring bracket I rests upon the planed top of the flange g of the
quadrant plate g and the centring bracket is further provided with a steel centre
point 2, which enters into a centre hole made truly in the axis of the stem of the
drill or other tool to be operated upon.
The method of procedure in grinding drills &c., with this modification, is the same
as previously described for ordinary flat drills or boring bits, except that the pin is
retained in position in the stock k and the rotating of the stock the necessary half
revolution, to bring both flanks under the operation of the grinding wheel, is effected
by rotating the sleeve k³, the adjustment for the necessary taper being made by the
screw stopf, and the diameter regulated, by adjustment of the screw h¹.
This modification is the one also used for grinding or sharpening reamers having
four, six, or any other number of sides, the collar or enlargement being provided
with the requisite number of holes equally spaced to correspond with the number of

page_text: sides of the reamer, the operation of the machine being conducted for this purpose in
the same manner as above described for grinding taper flat drills.
The modification of the machine shown by Figs. 6 and 7 is the one used for the
purpose of grinding twist drills, for this purpose the flat rest and centring bracket.
(Fig. 5) are removed and a V rest m substituted for supporting the cutting end of
the drill, this V rest is provided with a stem m¹ which passes into a hole or socket
bored at an angle of 45°,near the front end of the arm h in such a position that at whatever
required elevations the V rest may be fixed in the socket, the two bearing surfaces of
the rest m shall always be equidistant from the axial line of the rotating chuck k, and
a pinching screw m² is provided for securing the V rest at any required elevation, all
the other parts of the machine remain in position as described for grinding flat drills
or boring bits.
The operations for grinding twist drills are as follows, the diameter of the drill to
be ground being known the centring screw, is adjusted to half the diameter of the
drill, the same as previously described for adjusting to the stem of ordinary flat drills,
the rest m is then placed in the socket provided for it, and elevated or depressed,
until the side or fence m³ coincides with the point of the centring screw hand fixed
in that position by the pinching screw m² the stop pin fo is inserted into the one of the
several holes made in the flange f7 corresponding to the angle of the nose of the drill,
and the arm moved in that direction, until the stop piece g³ is in contact with the stop
pin, the cutting end or nose of the drill is then placed upon the V rest m, and the
side bracket i moved until the centre point of the centre enters the centre hole
formed in the end of the drill stom with the nose or cutting end of the drill, just clear
of the grinding face of the grinding wheel and the side bracket i is securely bolted to the
arm in that position the bolt j is now screwed down until the grippers 8, take a
firm bite upon the stem, taking care that during this operation, the cutting edge to be
ground is in as nearly a horizontal position as can be judged by the eye, and that the
body of the drill is held in contact with the two sides of the V rest m, the handle
screw j³ may now be slightly tightened to ensure that the centre point of the centre j
is well home in the centrehole, and the drill is now fixed ready for grinding operations,
with its axis truly in line with the gripping chuck.
3
The grinding wheel 6 may now be set in motion then by turning the screw i¹ the
nose of the drill will be brought into contact with the grinding face of the grinding
wheel b, and traversed across its face by the screw f¹.
If a proper adjustment of the screw is made, a cutting edge will be formed on the
end of the drill, having the requisite angle of clearance due to its being ground with
its axis in a plane above that of the axis of the grinding wheel as hereinbefore
described, in reference to the functions of the angle bracket d.
To perform the same operations upon the opposite cutting edge, the pin is taken
out of the stock and the stock partially withdrawn from the sleeve and the stock k
rotated a half revolution, and returned into the sleeve k³, the pin entering the hole.jⓇ in
the abutting flange, and then by gently pressing the stock home against the abutting
flange, the second cutting edge will be ground to the same angle and the same
length in relation to the axis of the drill, as the first, with a chisel point formed
truly intersecting that axis.
The next operation is to "back off" the material remaining behind the cutting
edge, and preserve the chisel point in the form left by the previous operation. This
is effected by turning the traversing screw f' until the point of the drill projects beyond
the edge of the grinding wheel, a distance about equal to half the width of the chisel
point, in which position, the drill is shown in fig. 6, and while in this position
rotating the drill upon its axis from left to right, by turning the sleeve k³ slowly a
distance equal to a sixth of a revolution, which is provided for by the dividing holes
in the collar k³, one side of the drill being thus ground, the same operation is repeated
upon the opposite side and the drill is truly ground.
"6
It will be evident from a consideration of the effect of this method of grinding
twist drills, that the result is not a backing off" to a uniform angle as has been
hitherto the common practice in grinding tools of this kind, but that there is first

page_text: formed a cutting edge having a clearance of about 10 degrees (or such other angle
as is due to the elevation of the plane of the axis of the drill above the axis of the
grinding wheel) this clearance extending from the cutting edge, to the plane of the
axis of the drill, and that the effect of "backing off" the material behind the cutting
edge by rotating the drill in the manner described is to form the remainder of the
clearance to the segment of a true cone, whose apex is the axis of the drill. Thus
there are formed two equal cutting edges projecting at an angle of 10 degrees more
or less according to the elevation at which the drill is fixed and the thickness of
metal in the centre of the drill from the conical seat or sole formed by the operation
of "backing off," this projection I find to be sufficient to equal the thickness of the
maximum shaving or cut which such drills are required to take, and by the nature of
the case, a drill so ground cannot be forced to take more than this maximum cut,
thereby reducing the risk of breakage of such drills, through the carelessness of the
workmen using them.
Although in the foregoing description of the method of "backing off," I have
described the method to be adopted to preserve a "chisel point" to the drill, I find in
practice that by conducting the operation of "backing off" without traversing the
point of the drill to project beyond the edge of the grinding wheel as shown in fig. 6
a prismatic point is formed which in some respects is practically superior to a chisel
point, correcting a slight inaccuracy which sometimes occurs, when the two spiral
grooves formed in such drills, are not of equal depth by forming a prismatic point truly
in the centre of the drill, and thereby also enabling the point to enter more truly into the
centre punch hole usually made for starting the drill, while the prismatic form of the
point appears to cut or scrape away the central portion of the metal to be drilled,
equally and in the same manner as a chisel point.
I prefer to use emery wheels such as 6 and to grind by the cylindrical face of the
wheel, but emery wheels or stones may be employed the disc face of the wheel being
used for grinding, in which case the wheel is or may be secured on the end of a
shaft placed horizontally at a right angle to the shaft 6 in suitable bearings the shaft
being at such angle in relation to the horizon and to the axis of the drill being ground
as to give the proper angle for clearance or backing off to the cutting edge as herein-
before explained.
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. The device constituting the gripping or holding chuck and used for taking hold
of the stem, or shank of the drill, rotating it upon its axis, and moving it into or with-
drawing it from contact with the grinding wheel, by the sliding in or out of the
sleeve substantially in the manner herein set forth and illustrated by figs. 1, 2, 3
and 4.
2. The arm carrying the said chuck provided with the device of the centring
screw used in combination with the gripping chuck k and side bracket i and having
longitudinal and lateral adjustments substantially as herein described and illustrated
by the drawings.
3. The horizontal quadrant plate or table provided with a movable flat rest, and
combined with the aforesaid arm substantially as and for the purposes herein described
and illustrated by the drawings.
4. The transverse slide for receiving the horizontal quadrant plate, provided with
the adjustable stops (f" and f) and combined with the bed or sliding way with the
adjustment for the purpose of rounding off the angles of the cutting edges of flat
drills, substantially in the manner herein described and illustrated by the drawings.
5. The centring bracket 1 (Fig. 5) for holding one end of drills, reamers, or other
tools which have to be supported in centres at both ends during the operation of
grinding combined with the chuck mechanism substantially as herein described and
illustrated by the drawings.
6. The construction and adjustment of the V rest m Figs. 6 and 7, having its line

page_text: of adjustment at an angle of 45 degrees with the horizontal, whereby the side or
fence (m³) is in contact with the body of the drill at the cutting end and opposite to
the cutting edge being ground substantially in the manner and for the purpose as
herein described, and illustrated by the drawings.
7. The elevating bracket d figs. 1 and 2 by means of which the drills or other tools
to be operated upon, may have their cutting edges formed with any required
amount of clearance by being ground with their axes at a greater or less distance
above the axis of the grinding wheel as herein described and illustrated by the
drawings.
8. The combination and arrangement of mechanism for forming the cutting edges
of twist drills with clearance and backing off, substantially as hereinbefore described
and illustrated by the drawings.
9. The combination and arrangement of mechanism substantially as and for the
purpose hereinbefore described and illustrated by figs 1, 2, 3 and 4 also the same
combination and arrangement when modified substantially as and for the purpose
hereinbefore described and illustrated by fig. 5 and also when modified substantially
as and for the purpose hereinbefore described and illustrated by figs. 6 and 7 of the
drawings.
Dated this Twenty second day of July 1887