Improvements in Drills and similar Tools.
Year: 1892

page_text: Date of Application, 18th Nov., 1892-Accepted, 14th Jan., 1893
COMPLETE SPECIFICATION.
Improvements in Drills and similar Tools.
I BRUNO WESSELMANN of 85/87 Mittelweg Borgfelde Hamburg in the Empire-
of Germany Manufacturer do hereby declare the nature of this invention and in-
what manner the same is to be performed to be particularly described and ascer--
tained in and by the following statement :-
This invention has for its object the production of a drill or similar tool preferably
for the working of metals which by means of the special formation of its cutting
edges possesses a higher effective power than the known borers and which furthermore
possess the great advantage of requiring no further preparation for use than.
grinding.
In the accompanying sheet of illustrative drawings
Figures 1, 2 and 3, and Figures 4, 5 and 6 show respectively in front and side.
elevation and plan, two different forms of drill.
Figures 7 and 8 show a so-called American or twist drill so that the difference of
the two cutting edges may be clearly demonstrated.
In a drill constructed according to this invention, the face or front planes are.
portions of a screw surface generated by a straight line z inclined at a considerable
angle to the axis xx of the drill (Figure 1) and are formed by grinding. The
edges of these faces are the curves tt of which the two diametrically opposite -
ones & form the cutting edges.
In the American and all other known drills the cutting edges are straight and at.
right angles to each other (see Figures 7 and 8). Practice has however shown that
a drill constructed on the foregoing principle possesses a higher value in working
than any of the known borers. This fact is based upon the concave or backward
bent cutting edges of the drill which work in a manner analogous to the known.
Thornycroft screw propellor whose generating line is curved backwards in the plane
of the axis and as is known works consequently more effectively than any other -
screw propellor.
The rolled section of the steel rod from which the borer is made, is shown in
Figures 2 and 5. In accordance therewith only the outside point of the cutting
edges falls on the periphery of a circle described about the centre of the drill so
that the profile appears somewhat tapering. By this means contact of the axial
surface of the drill with the outside of the drilled hole and the consequent so called
"of the drill is reduced.
wear
To facilitate grinding the axis of the drill may be indicated by a rib p on the -
concave sides of the profile.
The steel rods made to the shape shown can be sold in various diameters and the
production of the drill follows as pieces of the desired length may be cut off and.
ground.
Drills of the foregoing shape possess another advantage in their adaptibility to
be fitted with a tube filled with a lubricating substance, with or without a spray
head. This tube can be arranged against one or the other of the concave sides and
fixed to the drill shaft by rings or clamps and the lubricating substance flows out.
when warmed during the rotation and enables a continuous lubrication to be effected
without stopping the work.
Having now particularly described and ascertained the nature of my said inven--
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The method of producing drills consisting in rolling a steel rod with a section
formed of two similar concave and two similar convex sides laving opposite to each

page_text: other so that of the four edges two lay diametrically opposite to each other, in
cutting pieces of any required length from the said rod, and in grinding the pieces
at one end to serve as drills without any further preparation, the whole substantially
as described.
2. A drill manufactured substantially as described with symmetrical rounded
grooves on each side and having the faces or front planes at a sharp angle with the
axis and forming screw surfaces with concave curved cutting edges.
Dated this 18th day of November 1892.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.