IMPROVEMENT IN MACHINES OR APPLIANCES FOR GRINDING TWIST AND OTHER DRILLS FOR BORING METALS, ALLOYS, WOOD, IVORY, OR OTHER SUBSTANCES
Year: 1884

page_text: ANDREW SHIRLAW Engineer Suffolk Works Berkley Street Birmingham, do
hereby declare the nature of my invention for IMPROVEMENT IN MACHINES OR
APPLIANCES FOR GRINDING TWIST AND OTHER DRILLS FOR BORING METALS,
ALLOYS, WOOD, IVORY, OR OTHER SUBSTANCES, to be as follows:-
My invention consists of a grindstone and trough having a compound slide rest,
the upper portion carrying a bracket (adjustable or fixed) set at an angle of 120° to
the face of the grindstone, or any other convenient angle. This bracket supports
a plate having a tool holder to receive the drill-The plate, actuated by a handle,
swings on a centre which may be made adjustable, the distance from the fulcrum
to the centre and end of the drill determining the clearance to be given when
grinding. There are two stops on the face of the bracket to fix the angle of the
tool holder so arranged that the centre line of same shall when resting on the
lower stop pass through the centre line of the grindstone spindle, and this is an
essential feature of the Invention, as the straightness of the lip of the drill being
ground is thereby ensured-The toolholder is telescopic to adapt itself to different
lengths and contains a socket to receive the end of the drill provided with an
index for adjustment and fixing its position, so that the length of the two lips or
cutting edges shall exactly coincide when ground-There is also a provision for
fixing the position of the drill in the socket so that the lip shall be in the same
plane as the face of the grindstone.
The apparatus may be attached to existing grindstones or emery Wheels, or it
may be made in conjunction with either or both.

page_text: COMPLETE SPECIFICATION,
I, ANDREW SHIRLAW of Suffolk Works Berkley Street Birmingham in the
County of Warwick Engineer do hereby declare the nature of the said invention
for IMPROVEMENTS IN MACHINES OR APPLIANCES FOR GRINDING TWIST AND OTHER
DRILLS FOR BORING METALS ALLOYS WOOD IVORY OR OTHER SUBSTANCES, and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement, reference being had to the drawings
hereunto annexed and to the letters and figures marked thereon that is to say :-
My Invention consists of a grindstone and trough having a compound slide rest
the upper portion carrying a bracket (which is adjustable or fixed) set at an angle
of 120° to the face of the grindstone or at any other convenient angle. This
bracket supports a plate having a tool holder to receive the drill. The plate
actuated by a handle swings on a centre which may be made adjustable the
distance from the fulcrum to the centre and the end of the drill determining the
clearance when grinding.
There are two stops on the face of the bracket to fix the angle of the tool holder
so arranged that the centre line of same shall when resting on the lower stop pass
through the centre line of the grindstone spindle.
It being an essential feature of the invention that in the operation of grinding
the drill the longitudinal centre line of the drill shall be in the same plane as the
centre of the grindstone.
The tool holder is telescopic to adapt itself to varying lengths and contains a
socket to receive the end of the drill, provided with an index for adjustment and
fixing its position so that the length of the two lips or cutting edges shall exactly
coincide when ground. Or in place of the index I substitute a dividing arrange-
ment consisting of a loose collar with two notches and a spring catch so that when
one lip has been ground the tool holder can be turned so as to bring the other lip
in position to be ground. There is also a provision for fixing the position of the
drill in the socket so that the lip shall be in the same plane as the face of the
grindstone.
The plate upon the bracket may be dispensed with and the tool holder attached
to the bracket and work on a moveable sliding centre the holder having a slot
the clearance of the drill may be increased or diminished by altering the position
of a stud passing through this slot upon the tool holder.
A stud upon the holder working in a cam-shaped slot governs the form to be
given to the clearance of the drill.
An index rod is provided for the purpose of adjusting and regulating the distance
to the point of the drill as the stone wears.
The tool holder is prolonged and the end constructed to form a support with
a V shaped seating to support the drill the position of this support being adjustable
by a thumb screw.

page_text: I will now refer to the drawings in order to illustrate the nature of my said
Invention but I do not propose to confine myself to the precise details therein
shewn.
In the accompanying Drawings the same letters in each Figure represent the
same parts Figure 1 is a view of the machine from above and Figure 2 is a side
elevation of the same. (xx) is a grindstone and trough (a) is the compound
sliding rest carrying the bracket (b) set at an angle of 120° as shewn in Figure 1
(ccc) is the telescopic tool holder with its handle (d), (e) is the moveable sliding
centre (f) is the cam-shaped slot which governs the form to be given to the
clearance of the drill, (g) is the index rod for adjusting the distance of the point of
the drill as the stone wears, (h) is the prolonged portion of the tool holder to
support the drill, (i) is the loose collar and (2) the spring catch forming the dividing
arrangement in the tool-holder.
The apparatus may be attached to existing grindstones or emery wheels or it
may be made in conjunction with either or both.
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 combination of the several mechanical contrivances for the purpose of
grinding twist and other drills for boring metals alloys wood ivory or other
substances substantially as herein set forth and specified.
2. The mechanical arrangement by which I ensure the grinding of each lip of
the drill perfectly true and even with clearance suited to the work for which the
drill is required.
3. Constructing the several parts so that when starting to grind the longitudinal
centre of the line of the drill shall be in the same plane as the centre of the
grindstone in order to ensure the straightuess of the lips of the drill.
Dated this mon
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