Improvements in Tools for Drilling or Boring Holes with Inwardly Enlarged Diameters (or Undercut Sides).
Year: 1890

page_text: Date of Application, 17th Feb., 1890
Complete Specification Left, 15th Nov., 1890-Accepted, 20th Dec., 1890
PROVISIONAL SPECIFICATION.
Improvements in Tools for Drilling or Boring Holes with Inwardly
Enlarged Diameters (or Undercut Sides).
1, HENRY HILDITCH, of 3 Clifford Street, Whitmore Reans, Wolverhampton in
the County of Stafford, Joiner, do hereby declare the nature of this invention to
be as follows:-
This invention has for its object improvements in tools for drilling or boring holes
which it is desired shall have enlarged diameters inwards (that is undercut sides),
such holes, for instance, as are required to receive the soft metal plugs used in
adjusting weights, or for receiving the inner ends of rivets which are fixed to the
metal in which the holes are formed by being driven endways into such holes until
their inner ends spread out and fit into the enlarged diameters thereof.
A tool constructed according to this invention has a pair of fingers or arms pivotted
to a common holder which is carried by the drilling or boring apparatus or machine,
each formed with a cutting edge down one side, the two fingers together forming a
divided cutter. The cutting edges are shaped so that, when the tool is at work, they
are at the required degree of inclination from the axis of the hole. A hole to be
enlarged as described may be first sunk to a very shallow depth (in the process of
casting or otherwise) or may be formed to any depth not exceeding the full depth
required; the outer ends of the fingers are brought together sufficiently to allow
them to be entered into the hole, and when entered the tool is operated just as an
ordinary drill. The ends of the cutting fingers are slanted upwards from the cutting
edges aforesaid, and thus as the pressure is brought upon them the fingers are forced
outwards and undercut the sides of the hole. If the tool is to be used for deepening
a hole, in addition to enlarging it in diameter inwards, cutting edges are formed on
the ends of the fingers; but if the tool is to be used simply to enlarge the hole
inwards the ends are formed plain so that they bear on the bottom of the hole without
cutting. The fingers lie flat against one another near their outer ends, and thus
support one another in operation. Suitable means, such as a spring, are employed to
cause the automatic return of the fingers towards the axis of the hole immediately the
pressure is taken off, and thus the fingers can be readily drawn out of a hole and
inserted into another. Suitable means, also, such as an annular wedge screwed around
the holder and bearing against the fingers, or against parts formed thereon, are
employed for moving out the fingers against the sides of the hole in starting
the cut.
A convenient modification of this invention consists in pivotting the fingers hetween
the sides of a jaw on the end of the holder by means of a single pin, and forming
the sides of the fingers which are towards one another flat like scissors blades and
crossing the cutting portions. The upper or inner ends of the fingers are continued
beyond the fulcrum, and a rubber band is passed around them (or springs are fixed
in position to bear against them) and tends to draw them together and bring the outer
ends inwards towards the axis of the tool. A conical collar is screwed on the holder,
and the conical surface may be brought down to bear against the inner sides of the
upward extensions of the fingers, for the purpose of forcing them out and bringing
the cutting edges against the sides of a hole, when the drilling or boring operation is
commencing.
A tool constructed according to this invention may be used for forming a hole
which enlarges gradually inwards for the whole depth, or for merely undercutting or
enlarging the diameter of the inner end of such hole. When the fingers are formed

page_text: to cut depthways they do so in a flat, or approximately flat, plane and thus leave the
inner end of the hole flat, or approximately so, which for some purposes is a great
advantage.
11
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000
COMPLETE SPECIFICATION.
Improvements in Tools for Drilling or Boring Holes with Inwardly
Enlarged Diameters (or Undercut Sides).
I, HENRY HILDITCH, of 3 Clifford Street, Whitmore Reans, Wolverhampton in the
County of Stafford, Joiner, 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 :-
This invention has for its object improvements in tools for drilling or boring holes
which it is desired shall have enlarged diameters inwards (that is undercut sides),
such holes, for instance, as are required to receive the soft metal plugs used in
adjusting weights, or for receiving the inner ends of rivets which are fixed to the
metal in which the holes are formed by being driven endways into such holes until
their inner ends spread out and fit into the enlarged diameters thereof.
A tool constructed according to this invention has a pair of fingers or arms pivoted
to a common holder which is carried by the drilling or boring apparatus or machine,
each formed with a cutting edge down one side, the two fingers together forming a
divided cutter. The cutting edges are shaped so that, when the tool is at work, they
are at the required degree of inclination from the axis of the hole; and each finger is
in such position, in relation to the axis on which it is pivoted, that the reacting
pressure of the bottom of the hole in which the fingers are for the time operating
tends to force their outer ends apart so as to ensure their continuous effect in under-
cutting the hole. A hole to be enlarged as described may be first sunk to a very
shallow depth (in the process of casting, or otherwise) or may be formed to any depth
not exceeding the full depth required; but the hole should be formed to some slight
depth at least previously to operating with the undercutting tool, as such tool will not
start the hole from a plane surface, unless some means are adopted for temporarily
holding the fingers firmly together to prevent them spreading outwards, which would
however be inconvenient. The outer ends of the fingers are brought together suffi-
ciently to allow them to be entered into the hole, and when entered the tool is operated
just as an ordinary drill. The fingers are, preferably, pivoted with a common pin,
and the centre of such pin is on the axis of the tool; and such axis falls within the
outer extremity of each finger, and thus, as the pressure is brought against the ends
of the fingers, they are forced outwards and undercut the sides of the hole. If the
tool is to be used for deepening a hole, in addition to enlarging it in diameter inwards,
cutting edges are formed on the ends of the fingers; but if the tool is to be used
simply to enlarge the hole inwards, the ends are formed plain so that they bear on
the bottom of the hole without cutting. The fingers lie flat against or pass alongside
of one another, and thus support one another in operation. Suitable means,
such as
a spring, are preferably employed to cause the automatic return of the fingers towards
the axis of the hole immediately the pressure is taken off, and thus the fingers after
being drawn out of a hole are in position for insertion into another hole.
Having described the nature of this invention, I will now more particularly describe
the manner of performing it by reference to the accompanying drawings, of which
Figure 1 shews an elevation of a tool constructed according to this invention just
as it is commencing to cut into a shallow hole previously formed in a piece of
metal;
Figure 2 is a view at right angles to Figure 1;
Figure 3 is a view corresponding to Figure 1, but shews the tool to have cut some
distance into the piece of metal; and

page_text: Figure 4 is a section through the fingers or cutters hereinafter described, taken on
line of Figure 1.
The holder A is formed with a shank a to fit within the socket or head of a drilling
machine or brace, and with a jaw b within which the fingers or cutters are pivoted.
The fingers or cutters B B are pivoted within the jaw by means of the pin e, and
have cutting portions c extending downwards or outwards from the fulcrum and
crossing one another as shewn, and non-cutting portions d extending upwards or
inwards from the fulcrum. The nearer side of the jaw is shewn to be cut away in
Figure 3, to shew more clearly the entire shape of the fingers or cutters. The edges
marked' (see especially Figure 4) are the edges which undercut the hole. It will
be seen that the cutting portions c of the cutters incline outwards from the central
axis of the tool, and thus the reacting pressure of the bottom of the hole tends to
constantly force the cutters outwards, and such outward force, together with the
inclination of the cutting edges h, causes the undercutting of the hole. The portion
of the holder between the shank a and jaw b is screwed to receive an internally screwed
conical collar C. This collar has a milled edge f to facilitate the screwing it along
the holder. An indiarubber band 9 (shewn in section only, for convenience) is
passed around the upper ends of the extensions d of the cutters, and tends to draw
them together and bring the outer ends of the extensions or cutting portions c
inwards towards the axis of the tool. The conical surface of the collar C forms a
stop to the inward position of the parts d of the cutters, and consequently to the
inward position of the cutting parts of the cutters; and the lower or outer ends of
such cutting parts may be moved outwards, into the position required to enter any
particular hole, by simply screwing the collar along the holder so as to wedge out the
portions d of the cutters against the pulling in force of the rubber band. This collar
is chiefly for the purpose, however, of preventing the cutters, when they have been
shortened beyond a certain point by wear, from moving sufficiently inwards at their
upper or inner ends to bring their outer ends into such position, in relation to the
pivot axis, that they will not be moved outwards by the reacting pressure of the
bottom of the hole; except for this purpose, the collar (or equivalent means) is not
necessary though it is convenient. The bottom or outer ends of the cutters are
slanted off at a somewhat acute angle, as shewn, with the undercutting edges, when
the tool is required for a flat, or approximately flat, bottomed hole. The tool may
be used simply to undercut for the whole depth, or merely for a short depth from
the bottom, a hole already formed to the required depth; but a hole may, of course,
be enlarged as well as undercut, by simply continuing the operation of the cutters
to the necessary extent. If it is desired to deepen, as well as undercut the hole, the
outer ends of the cutters are formed with cutting edges also, as shewn, and then the
tool cuts downwards and outwards at the same time. The cutting depthways is per-
formed, when the ends of the cutters are shaped as shewn, in a flat or approximately
flat plane, leaving the inner end of the hole flat, or approximately so, which for some
purposes is a great advantage. In the case of weights and other castings in which
such may be convenient, it is an advantage to form, in the process of casting, shallow
flat-bottomed holes of somewhat less diameter than the intended finished diameter at
the top, and these shallow holes are then finished out by the tool. The tool may,
however, be used also for holes which have been previously drilled in the usual way,
and the outer ends of the cutters may be formed to any required shape for drilling or
boring a hole of any desired shape at the bottom and any desired shape in the undercut
part. The sides of the parts c of the cutters which are towards one another are flat
like scissors blades (see more especially Figure 4) and bear flat against each other
where they cross; and thus, as the cutters, when shaped in section as shewn by
Figure 4, revolve in the direction indicated by the arrow marked on such figure,
they afford one another mutual support.
It is not, of course, essential to pivot the fingers to the same pin, as each may be
pivoted to a separate pin. Such an arrangement, however, is not so convenient as
that illustrated, as the centres of the pins would be at some little distance on opposite
sides of the central axis of the tool, besides unnecessary complication being introduced.

page_text: 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. A tool for drilling or boring holes with inwardly enlarged diameters (or under-
cut sides), having a pair of pivoted cutters of which the undercutting edges incline or
project outwards from the central axis of the tool, and of which the outer ends also
are formed with cutting edges if desired, substantially as described, for the purpose
set forth.
2. A tool for drilling or boring holes with inwardly enlarged diameters (or under-
cut sides), having a pair of pivoted cutters which expand automatically within a hole
while in operation, substantially as described.
3. A tool for drilling or boring holes with inwardly enlarged diameters (or under-
cut sides) constructed and operating substantially as described with reference to the
drawings herewith, and with or without the ends of the cutters formed to deepen a
hole when in operation therein, as described.
Dated this 14th day of November 1800
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicant.