IMPROVED APPARATUS FOR SHAPPENING DRILLS
Year: 1881

page_text: LETTERS PATENT to Edmund Ernest Bentall, of Fullbridge Works, Maldon, in
the County of Essex, Tool Maker, for an Invention of "IMPROVED APPARATUS
FOR SHAPPENING DRILLS."
PROVISIONAL SPECIFICATION left by the said Edmund Ernest Bentall at
the Office of the Commissioners of Patents on the 13th April 1881.
EDMUND ERNEST BENTALL, of Fullbridge Works, Maldon, in the County of
Essex, Tool Maker. "IMPROVED APPARATUS FOR SHARPENING DRILLS."
The chief object of this Invention is to sharpen what are known as
" twist
drills," the cutting edges of which are formed from a coned point, and stretch
across the drill from opposite sides to the axis. To sharpen these edges each edge
is presented in turn to the action of the emery wheel or grindstone at a suitable
incline corresponding to the inclination of the coned surface. If the wheel were
to act upon the drill only when the drill was stationary, a plane or regular surface
would be ground. It is however necessary to cause the wheel to bevil off the
backing from the cutting edge, and it is to effect this object that my improved
apparatus is designed.
In front of the grinding wheel I mount a sliding saddle upon a suitable bed or
support, and fit it with a traversing screw.
This saddle I cast with a bearing ring
set diagonally to the line of traverse of the slide, and in this bearing I fit a short
cylinder capable of receiving an axial motion. This cylinder I bore diagonally to
receive a sleeve which serves as a drill holder, its axis being so arranged as to
converge to the axis of the cylinder. This sleeve is fitted with bushes of various
sizes to receive different diameters of twist drills, and means are provided for
arresting the axial motion of the sleeve when it has received half a turn. Provision
is also made for limiting the axial motion of the cylinder. The drill when inserted
in place is advanced through the sleeve until its point touches a removable stop
or gauge which indicates the point where the axes of the cylinder and the sleeve
meet, and it is then made fast in the sleeve. To sharpen the drill it is only
necessary to secure it in one or other of its axial positions, and then to advance it

page_text: into contact with the grinding wheel. This wheel will then grind from the cutting
edge downwards, and while this operation is proceeding an axial motion is to be
given to the cylinder. This will move the drill laterally towards the wheel, and
thus the backing will be chamfered off to an extent equal to the lateral movement
of the drill. By reversing the movement of the cylinder, and drawing back the
slide, the apparatus will be ready for readjustment to bring another cutting edge
under the action of the sharpening wheel at the next advance of the slide towards
that wheel.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edmund Ernest Bentall in the Great Seal Patent Office on the
13th October 1881.
EDMUND ERNEST BENTALL, of Fullbridge Works, Maldon, in the County of
Essex, Tool Maker. "IMPROVED APPARATUS FOR SHARPENING DRILLS."
The chief object of this Invention is to sharpen what are known as "twist drills,"
the cutting edges of which are formed from a coned point, and stretch across the
drill from opposite sides to the axis. To sharpen these edges each edge is presented
in turn to the action of the emery wheel or grindstone at a suitable incline corre-
sponding to the inclination of the coned surface. If the wheel were to act upon
the drill only when the drill was stationary a plain or regular surface would be
ground. It is however necessary to cause the wheel to bevil off the backing from
the cutting edge, and it is to effect this object that my improved apparatus is
designed.
In front of the grinding wheel I mount a sliding saddle upon a suitable bed or
support, and fit it with a traversing screw. This saddle I fit with a vertical ring
bearing or its equivalent, setting it diagonally to the line of traverse of the slide,
and in this bearing I mount a segment shaped carrier in such a manner as to permit
of its moving axially in the bearing.
This carrier is intended to receive the drill to be sharpened, and to present the
cutting edges of the drill in succession to the emery wheel, giving the drill while
it is moved over the face of the emery wheel a slight axial motion.
The drill is held in the carrier in such a position that its axis will lie at an
angle to the axis of motion of the carrier. The point at which these two axes
cross each other will be in rear of the drill point, and the position of the drill
when placed for sharpening will be such that the plane of the axis of the drill will
be in a horizontal plane slightly below the horizontal plane of the axis of the
carrier.
In the accompanying Drawing, Fig. 1 is a plan view of the drill sharpening
apparatus, and Fig. 2 is an end elevation of the same, the emery wheel being shewn
in position in both Figures as acting upon the drill; Fig. 3 is a vertical section

page_text: of the apparatus taken in the line 1, 2, of Fig. 1; and Fig. 4 is a face view of the
carrier detached.
In these Figures, A is the saddle, to which the annular bearing B is bolted, a
portion of the ring being removed to lighten the bearing.
Fitted to this bearing is the segment shaped carrier C, which, as shewn in the
cross, section, Fig. 3, embraces the bevilled edges on the outer and inner periphery
of the bearing, and is free to slide over the back face thereof, c being a detachable
piece to provide for the fitting of the carrier to the bearing and its removal_
therefrom.
This carrier is cast with or has attached to it a bracket guide C¹ projecting
from its rear face, and serving to carry an adjustable headstock C, in which is
mounted a holder C³. This holder C is capable of turning in bearings in the
headstock, and is intended to receive the shank of the drill to be sharpened.
Mounted loosely on the holder and capable of being made fast thereto by a
binding screw c¹ is a dividing wheel C which is notched to correspond to the
cutting edges of the drill, its object being to regulate with precision the presentation
of the cutting edges of the drill to the emery wheel or grindstone.
The bracket C is slotted longitudinally to receive a tightening screw which
holds the headstock C³ firmly in its adjusted position.
On the front side of the carrier C is cast or attached a projection which forms a
guide C³ for the reception of the rear ends of a pair of gripping jaws C, which are
free to slide therein, and are intended to hold the drill firmly under the action of
the emery wheel.
The rear ends of these jaws are threaded to receive a right and left handed
screw C which has its bearings in the guide C³ and in a plate attached thereto.
This screw is held in place at one end by locking nuts, and at the other by a
thumb piece, through which an axial motion is imparted to the screw for tightening
and slackening the grip of the jaws.
D is the twist drill to be sharpened, and E is the emery wheel or grindstone for
sharpening the cutting edges.
The axis of this wheel lies parallel to the line of traverse of the saddle A.
It should be remarked that in the relative positions of the centre lines of the
carrier and the drill, and the position in relation to the line of traverse of the drill
of the grinding wheel lies all the efficacy of the grinding.
The carrier C is fitted with a handle C8, by means of which it is turned in its
bearing while the sharpening of the tool is proceeding. To limit this axial motion
of the carrier the bearing B is provided with a stud pin which projects through a
segment slot in the carrier, as shewn at Fig. 2.
In working with this apparatus I proceed as follows:-I insert the shank of the
drill in the holder C³, and shift the drill forward in its holder until its point
reaches a removable stop on the saddle that gauges the proper distance for its
advance.
When the drill has taken up its proper position I tighten. the gripping jaws C
upon it, and thereby secure it firmly on to the carrier. At this time the dividing.
wheel may be assumed to be loose upon the holder, but locked in position by its
spring retaining catch. I now, by means of the binding screw c¹, tighten this
wheel upon the holder, and thereby ensure the moving of the holder with its
drill as the dividing wheel is turned to shift the position of the cutting edges of
the drill, and hold one or other, as the case may be, under the action of the grinding
wheel.
To facilitate the turning of the dividing wheel the binding screw c¹ is extended
to form a handle, by pressing which to the right or left the notches of the dividing
wheel may be severally brought into coincidence with the locking catch.
Supposing now the grinding wheel to be rotating in the direction of the arrow,
Fig. 2, I move the saddle A forward by means of its traversing screw, and at the
same time by means of the handle Os turn the carrier in the direction of the arrow
and with it the drill, thereby causing the cutting edge of the drill to move past the

page_text: grinding surface, and thereby enable the grinding wheel to bevil off the backing
from the cutting edge.
When this is effected I restore the carrier to the starting position of Fig. 2, and
I then give a half turn to the drill for the purpose of presenting its second cutting
edge to the grinding wheel. This shifting of the drill I effect by pulling over the
dividing wheel so as to make its spring stop catch into the second notch when the
drill will be held in its second position.
The apparatus is now ready for the sharpening of the second cutting edge, which
is effected by traversing the saddle as before, and simultaneously giving an axial
motion to the carrier in the direction of the arrow, Fig. 2. By thus moving round
the carrier I am enabled to ensure an identity of action of the cutting wheel upon
the opposite sides of the drill point.
It should be remarked that the slide which carries the saddle must itself be
capable of receiving a forward movement in order to feed forward the drill and
bring it into contact with the grinding wheel.
When the sharpening of the drill is completed the gripping jaws are opened
and the drill may be removed from the apparatus.
Having now set forth the nature of my Invention of "Improved Apparatus for.
Sharpening Drills," and explained the manner of carrying the same into effect, I
wish it to be understood that under the above in part recited Letters Patent I
claim,―
The arrangement of apparatus above described for presenting drills to be sharpened
to the cutting wheel in such a manner as will ensure the equal removal or bevilling
off of the backing from the cutting edges thereof, as explained.
In witness whereof, I, the said Edmund Ernest Bentall, have hereunto set
my hand and seal, the Tenth day of October, in the year of our Lord One
thousand eight hundred and eighty one.