Improvements in or connected with Hand and Machine Rock Drills, and Hand and Machine Rock Drill Bits, and Analogous Drilling or Boring Apparatus.
Year: 1898

page_text: Date of Application, 2nd Sept., 1898
Complete Specification Left, 2nd June, 1899-Accepted, 15th July, 1899
Improvements in or connected with Hand and Machine Rock
Drills, and Hand and Machine Rock Drill Bits, and Analogous
Drilling or Boring Apparatus.
We, RICHARD NICHOLSON and ROBERT JAMES NICHOLSON, trading as John Nicholson
& Sons, of Mowbray Steel Works, Sheffield, in the County of York, Steel Manufac-
turers, and DONALD MCKENZIE, of Randfontein Estate, near Johannesberg, in the South
African Republic, but at present residing at the Albany Hotel, Sheffield, aforesaid,
Contractor, do hereby declare the nature of this invention (communicated to us from
abroad by William Muat MacFarlane, of Randfontein Estate, aforesaid,) to be as
follows:-
-
Our said invention relates to improvements in or connected with hand and machine
rock drills, hand and machine rock drill bits and analogous drilling or boring apparatus.
The object of our invention is to reduce the labour and cost of handling and
operating the machines in the nines avoiding the somewhat costly process of re-
sharpening the drills, and to effect improvements in the construction of the drills or
bits.
In carrying our invention into effect we provide a drill so constructed that the drill
or cutting extremity is readily attachable to and detachable from the holder or shank.
To effect this we split the holder or shank in one or more convenient directions and
arrauge to expand the same by means of a suitable taper bolt, or bolts or wedges so
that the inserted cutting tool is securely held in position by reason of the expanded
dove-tailed jaws of the holder being brought to bear against abutments on the
cutter.
We do not confine ourselves to the exact method described of securing the cutter or
drill to the shank as this may be varied. For instance instead of holding the cutter
by the expanded jaw of the holder or shank we might arrange for the jaw of the
holder to embrace the cutter and securely hold it in position by the natural
spring of the split end of the holder, assisted if desired by means of a screwed
bolt which can be operated to bring the jaws of the holder together.
Or, instead of splitting the holder, we might form the same with a bored out recess
to receive a corresponding shank or projection on the back of the cutter and secure
the same in the holder by means of a set screw.
Under our invention instead of having to remove the combined drill and holder and
carry the same out of the workings to be sharpened when required, the cutter merely
requires to be removed and replaced with a fresh one when required.
The detachable cutters are provided with one or more cutting faces or surfaces so
that as one working surface becomes blunted by use the cutter can be turned in the
holder so as to bring a fresh cutting face into operation.
The cutter for instance may be formed square so as to be provided with four
cutting surfaces.
One form of our detachable cutters or drills is provided with four cutting faces with
cutting or knife edges of |--| shape. The longitudinal central web is provided with
cutting edges by bevelling off the outer edges. This may be done throughout the

page_text: length of the web or the web may be formed with two opposite cutting edges by
formning it with two oppositely arranged bevels.
This would introduce another cutting edge at the point where the opposite
bevels meet in the length of the web. Transverse outer cutting edges are formed
by bevelling the outer edges of the opposite parallel limbs of the - shaped
cutter.
A modified form of, cutter may be obtained by continuing the central web of the
shaped cutter a distance beyond the transverse parallel limbs. This would form
a double star or cross which would be very effective owing to the six cutting points
presented by the six points of the double cross. This cutter may also be formed with
two or more working surfaces.
Improvements in or connected with Hand and Machine Rock
Drills, and Hand and Machine Rock Drill Bits, and Analogous
Drilling or Boring Apparatus.
We, RICHARD NICHOLSON and ROBERT JAMES NICHOLSON, trading as John
Nicholson & Sons, of Mowbray Steel Works, Sheffield, in the 'County of York,
Steel Manufacturers, and DONALD MCKENZIE, of Randfontein Estate, near
Johannesberg, in the South African Republic, Contractor, do hereby declare the
nature of this invention (communicated to us from abroad by William Muat
MacFarlane, of Randfontein Estate, aforesaid), and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement and accompanying drawings :-
-
Our said invention relates to improvements in or connected with hand and
machine rock drills, hand and machine rock drill bits and analogous drilling or
boring apparatus.
The object of our invention is to reduce the labour and cost of handling and
operating the machines in the mines avoiding the somewhat costly process and
delay occasioned by the re-sharpening of the drills, and also to effect improve-
ments in the construction of the drills or bits.
In carrying our invention into effect we provide a drill so constructed that the
drill or cutting extremity is interchangeable so as to readily attach the same to
and detach it from the holder or shank.
And in order that our invention may be fully understood we have attached hereto
three sheets of illustrative drawings.
Fig. 1 shows in elevation a holder or shank with a detachable and interchangeable
cutter in position.
Fig. 2 is a plan of same.
Figs. 3 to 9 show modified constructions of drill holders.
The remaining figs. indicate various forms of cutters.
In constructing our improved holder and detachable cutter we split the holder or
shank a as shown at a' in the plan view Fig. 2. The holder is thus provided with flexible
jaws. These jaws are formed with dovetails or inclines a² a² (see Fig. 2) which are
adapted to engage with corresponding dovetail abutments b formed on the cutter c.
taper bolt d or wedge is inserted in a corresponding taper hole or recess in the

page_text: slit a¹ formed in the holder so that the jaws of the holder « can be readily expanded
in the direction of the arrows. The expanded dovetailed jaws of the holder a are thus
brought to bear with great pressure against the abutments 6 of the cutter c and the
same is thus securely gripped and held in position in the holder. More than one such
taper bolt or wedge could be employed if desired, or one longitudinal wedge
occupying the entire length of the slit a¹ could be used.
A modified method of expanding the jaws of the holder a is shown in Figs. 2^
and 2B. In this case instead of a taper bolt we take a cylindrical bolt d and split it
angularly as shown in Fig. 2ª. The tapered end of each half of the bolt d is inserted
through the hole in the slit a¹ at opposite sides of the holder a. The halves of the
bolt d thus slide upon each other and act as wedges to expand the jaw of the holder a
as shown in Fig. 2B.
In Fig. 9 we show another method of expanding the jaws of the holder a. The
wedge in this case is of U shape and is driven in position by means of a cotter
introduced at the enlarged end marked * of the slit a¹.
C
The jaws of the U shaped wedge when in position embrace the web c¹ of the
cutter and the web thus acts to prevent the wedge d from falling out of the slit.
Instead of expanding the inclined sides of the holder against dovetailed abutments
on the cutter we may use the arrangement shown in Fig. 3 in which the natural
spring of the slit a¹ of the holder « acts to grip the rib c¹ of the cutter c and securely
hold same assisted by means of the bolt a² and nut a³ by means of which the jaws of
the holder can be contracted.
In this arrangement the ribs c¹ of the cutter c are slightly bevelled inwards and
the jaws of the holder a are formed with corresponding inclines a shown more
clearly in Fig. 4, thus serving to retain the cutter in position within the holder.
Instead of using a nut as shown in Fig. 3 we may employ a taper pin a engaging
with a taper recess in the bolt a² as shown in Fig. 4.
In Figs. 5 to 9 we show modified methods of constructing the holder a. In these
cases the holder is formed in two separate halves to obtain the expandable jaw by
means of which the cutters are secured in position. Fig. 5 shows a longitudinal view
of the separate halves of a holder, Fig. 7 is an end view showing the expandable
slit and aperture a² to accomodate the web c¹ of the cutter c. Fig. 8 is a plan
view of Fig. 5 with the cutter removed and the holder broken in length."
The two halves of the holder a are welded to a suitable shank, being hollowed or
flared out at the ends a³ to embrace the shank, as shown in the end view Fig. 6.
In Fig. 9 the split halves of the holder a are formed at a¹ to fit into a socket of a
suitable shank and are secured therein by means of a pin or other suitable means.
The interchangeable and detachable cutters are formed with one or more cutting
faces of shape. In Figs. 1 to 3 a cutter is shown having four cutting faces.
The cutter having four cutting faces is shown more clearly in Figs. 10 to 12.
Figure 10 shows a face view of the shaped cutter c. The cutting faces of the
cutter c are formed by the knife edges d'd¹ d².
The longitudinal central cutting edge d is formed by bevelling off the outer edges as
shown more clearly in the plan view Fig. 11 and cross sectional view Fig. 12.
The outer transverse cutting edges are formed by bevelling off the outer
edges inwardly or transversely. As shown in Figs. 1 and 2 the expandable jaw of
the holder a abuts not only against the dovetail abutments b but also against the
longitudinal central cutting edges at each side of the jaw. In Figs 13 to 15 we show
a cutter of formation as described but with two cutting faces only.
In this case
there is no central web or cutting edge to abut against the ends of the holder as in
Fig. 2 but we arrange for the transverse cutting edges d¹ d² not in use to abut against
the shoulder a' of the holder a as shown in Fig. 5, the central web c¹ also bearing
against the holder in the socket a².
This cutter could be made long enough to admit of resharpening and if provided
with one cutting face the end socketted in the holder could be formed with flat faces
to abut against corresponding flat shoulders formed on the holder.
A further modified form of cutter is shown in Figs. 16 to 19.

page_text: This form is obtained by means of a design in all respects similar to the cutter
already described save that the central web e of the - formation is produced
at el e² beyond the transverse parallel limbs ff. This forms a double star or cross
and is very effective providing 6 cutting edges numbered 1 to 6 in the drawings.
In Figs. 16 to 19 the cutter is formed with two cutting surfaces although it may
be formed with one only or four if desired. Fig. 17 shows the bevelled abutments b
for the reception of the expandable jaws of the holder a.
Fig. 18 is a plan view of the cutter showing the bevelled edges of the extended
portions e¹ of the web e.
Fig. 19 is a cross sectional view on the line x-x.
Fig. 17, showing the cutting edges of the web e.
Under our invention instead of having to remove the drill and holder and carry
the same out of the mines when the cutter is blunted, where a cutter having more
than one cutting face is used, the cutter can at once be reversed to bring a fresh
cutting face into action. If all the faces are exhausted, or if the cutter has but one
cutting face, the cutter merely requires to be removed and replaced by a fresh one,
a stock of which could be kept ready at hand. The cutter only thus requires to be
renewed instead of the whole drill as was formerly the case.
Our invention is thus designed to effect a material reduction in the initial cost of
the drills or tools as the detachable cutters are readily interchangeable with the
holders. Moreover the cost of handling in the mine is reduced, avoiding the costly
process of resharpening the drills.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
1) In combination with an interchangeable and detachable cutter for rock drilling
and analogous drilling or boring apparatus, a holder formed in one or two parts
provided with a flexible jaw by means of which the holder is securely attachable to
the cutter and detachable therefrom in the manner by the means and substantially
as described and shown.
2) The improved interchangeable and detachable cutter for apparatus of the
indicated nature provided with one or more cutting surfaces of |- - shape and dove-
tail abutments to secure the cutter to the tool holder substantially as described and
illustrated.
3) The modified form of detachable cutter in which the central web of
the - formation is produced beyond the opposite parallel limbs so as to form a
double star or cross, substantially as described and illustrated.
Died this 1st day of June 1899
tod this 1st day of June 1899.
For the Applicants,
E. K. DUTTON & Co.,
Chartered Patent Agents, 5, John Dalton Street, Manchester.