An Apparatus for Grinding Twist Drills and other Tools of a similar Nature with True and Correctly Formed Cutting Edges.
Year: 1886

page_text: Date of Application, 4th Mar., 1886.
Complete Left, 3rd Dec., 1886.
Complete Accepted, 7th Jan., 1887.
An Apparatus for Grinding Twist Drills and other Tools of a similar
Nature with True and Correctly Formed Cutting Edges.
I GEORGE PERCIVAL SMITH Esquire 7 Calverley Park Gardens Tunbridge Wells
do hereby declare the nature of this invention to be as follows:-
An apparatus for grinding twist drills & other tools of that nature with true &
correctly formed cutting edges. Its advantage consists in the simplicity of its actiou
its adaptation for use with an ordinary grindstone if desired.
It consists of a frame fixed to a horizontal bench conveniently near to the stone.
To this frame & between two similar upright guides is hinged a frame which moves
in the vertical plane perpendicular to the side of the stone & passing through its
axis.
In this frame is fitted a cylinder or body of revolution of some other form which
can be rotated in the latter frame by means of a lever the axis of the cylinder being
in the aforesaid vertical plane & inclined at an angle of about 50. This cylinder is
bored to receive a drill or a holder to grasp that or any other sized drill, the axis of
the bore, which coincides with that of each drill, being inclined at an angle of about
10° to the axis of the cylinder and intersecting it on the horizontal surface of the
grindstone.
From the frame an arm projects in which is fixed a shaft carrying a wheel which
rests on the stone. If a drill be now fixed in the bore so that the edge of its cutting
lip rests on the stone and the stone is made to revolve, the wheel which runs close to
the point of the drill will regulate the grinding & allow the drill to rise & fall
with the inequalities of the stone; and if the cylinder be simultaneously rotated
through an angle of 90°, the inclination of the drill to the stone will be gradually
increased owing to its excentrically inclined position with regard to the axis of the
cylinder and the result will be that this lip of the drill will be ground with the
required clearance of (say) 10". If now the drill be loosened & turned round 180°
and refixed in the bore and the cylinder also rotated 180°, which will bring the edge
of the second lip of the drill into the same position as previously occupied by the
edge of the first, and if the process of grinding simultaneously with a gradual rota-
tion of the cylinder through 90° be repeated, the drill will be evenly ground and with
a similar clearance on both lips.

page_text: The most important part of my invention consists in the drill being excentrically
inclined to the axis of the rotating cylinder as above stated. The apparatus is most
conveniently placed for use as above described, but it can be used in other positions,
and detached from the horizontal frame can be guided by the hand with or without
the support of additional wheels or guides.
The angles of 50" & 10" are merely chosen for illustration, not probably being
accurately correct and in practice the edge of the drill should be a little below the
wheel so as to allow of some grinding before the wheel comes down on the stone.
This will not only sharpen the cutting edge, but give it a better form for entry. By
the point of the drill is meant not its real chisel shaped termination but the point
where the lines of its entting edges would intersect.
For grinding large drills, and the method is equally applicable to small ones I
modify my invention by boring the cylinder straight through the axis, to receive the
drill & by connecting the frame with the horizontal frame by means of one or
more circular arms moving in corresponding circular slots, all having the point of
the drill for a centre, and the plane of motion being that of the vertical plano
aforesaid this connection being instead of the hinge before mentioned.
When the drill is placed as in the first case & the cylinder rotated through the
angle 90 simultaneously with the motion of the frame radially through the angle of
10 the lip of the drill will as before be ground with the required clearance of 10" :
and so for the other edge of the lip as in the former case.

page_text: An Apparatus for Grinding Twist Drills and other Tools of a similar
Nature with True and Correctly Formed Cutting Edges.
I GEORGE PERCIVAL SMITH 7 Calverley Park Gardens Tunbridge Wells Esquire
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
My invention consists of an apparatus for grinding Twist drills and other tools of
that nature with exact and uniform cutting edges.
It consists of a frame K W L fixed to a horizontal bench or other support near or
fixed to the frame of the grindstone of which X Y is the horizontal surface, on which
the drill is ground.
In this frame and between two similar upright guides of which G WH is the front
one, is hinged at Gà frame ABCD which can move on the hinge in the vertical
plane perpendicular to the side, and passing through the axis of the stone. In this
frame ABCD is fitted a cylinder or other body of revolution QTS R which can be
rotated in the frame by means of a shaft P fixed in the cylinder and terminating in
the handle R. The axis of the cylinder being in the aforesaid vertical plane, and
inclined to X Y at an angle of about 50".
This cylinder is bored to receive a drill FS, the axis of the drill being inclined to
that of the cylinder at an angle of about 10", represented by the angle (fig. 1) F S U,.
the two axes intersecting at S in the line XY. From the frame ABCD there
extends an arm CV in which a shaft M is fitted containing a wheel N which rests on
the grindstone and revolves in the same plane. If a drill be fixed in the bore so that
the edge of the cutting lip rests on the stone in the line X Y, and the grindstone he
turned the cylinder being at the same rotated by means of the handle R', the effect
will be to force the lip of the drill down upon the stone, more towards the outside of
the drill, and less towards its axis, and the result will be that the lip will be ground
with a required clearance of about 10. The wheel N running on the stone close to
the point of the drill regulates the grinding, which can be greater or less, by means
of an adjusting screw on the shaft M. It also neutralizes the effects due to inequali-
ties of the stone. If the drill be withdrawn, turned through an angle of 180" and
refixed in the bore the other and opposite lip will be ground in the saine manner, and
thus the drill will be evenly formed as to both lips. The most important part of my
invention consists in the drill being fixed eccentrically in the rotating cylinder as
above described. This tool is most conveniently placed as above described but it can
be used in other positions on the grindstone or emery or other wheels and whether of
a cylindrical or plane or other form. To fix the drill in required position a Collar O is
fixed on it, in the lower side of O, are inserted two projections Z, Z, 180° degrees apart.
A slot Z in the upper face of the cylinder QTSR receives the projection Z for one
position of the drill, and the projection Z' for the other position. On the shaft P. is
fitted a milled Collar E in which is cut a thread fitting a screw thread on P. This
milled Collar on being screwed down presses on the shoulder of the Collar O and thus

page_text: clamps the drill immoveably in the cylinder. On reversing the screw motion, the
milled Collar moves upwards so as to allow the Collar O with the drill, to be with-
drawn and refixed at an angle of 180° as above described, and again clamped. The
frame GW H is made to slide in a grooved plate K' L' by means of an arm or crank
attached to the cylinder and connected with K' L' at I, by the rod k so that as the
grinding proceeds and the cylinder is simultaneously rotated, the frame ABCD with
the drill is moved forward. By this means the drill not being confined to one cylin-
drical portion of the grindstone, is prevented from unequally wearing and furrowing
the stone.
The angles of 50°, 10°, and 90%, are not necessarily the correct angles but are
selected for the purpose of illustration. For the same reason I have spoken of the
drill as fitting the bore, though this bore is better fitted with a chuck or other device
for holding drills of various sizes. The term cylinder also, is used for any solid of
revolution, or any body, parts of which could belong to such solid.
In practice, the edge of the cutting lip is generally better not to be exactly in the
line XY when the grinding commences, but advanced more or less, according to the
degree of bite required to be given to the entting lips. This is effected by an adjust-
able slot mn attached to ABCD in which slides a pin h affixed to the cylinder aty.
The position of this slot determines the point on the stone at which the grinding is to
commence and its length, say 90" more or less, the angular superficies of each lip to
be turned towards the grindstone, without intruding on or injuring the edge of the
other lip.
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 excentric position of the drill in the rotating cylinder or other body as
aforesaid, by means of which the required clearance and cutting edge is given in the
grinding.
(2) The regulation of the grinding and of its amount by means of the adjustable
wheel as aforesaid.
(3) The prevention of unequal grinding due to inequalities of the surface by means
of the wheel concurrently raising or lowering the drill as aforesaid.
(4) The action of the milled collar in clamping and unclamping the drill as
aforesaid.
(5) The automatic transference of the drill to different parts of the grinding
surface, by the slide and crank, as aforesaid.
(6) The general plan of the apparatus as aforesaid, with the combination of all
or any of these arrangements.
PERCIVAL SMITH