IMPROVEMENTS IN SCREW-CUTTING GEAR.”
Year: 1873

page_text: LETTERS PATENT to Charles Thieme Liernur, C. M. De Bruyn Kops,
Civil Engineers, and Johann Martignoni, Mechanical Engineer, all
of Frankfort-on-the-Maine, in the Kingdom of Prussia, for the In-
vention of "IMPROVEMENTS IN SCREW-CUTTING GEAR.”
PROVISIONAL SPECIFICATION left by the said Charles Thieme Liernur,
O. M. De Bruyn Kops, and Johann Martignoni at the Office of the
Commissioners of Patents, with their Petition, on the 7th May
1873.
We, CHARLES THIEME LIERNUR, C. M. DE BRUYN KOPs, Civil
Engineers, and JOHANN MARTIGNONI, Mechanical Engineer, all of
Frankfort-on-the-Maine, in the Kingdom of Prussia, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN SCREW-CUTTING
GEAR," to be as follows:-
-

page_text: The clip E turns on a pivot P, and is fastened with a conical pin Fas
before, and on being brought into the position shown by the dotted lines
the dies can be inserted or removed. These improved forms of screw
stocks are of course independent of the dies used, and the peculiarity
that any kind of dies belonging to a scrow stock with two dies can be
used with them is a part of the present improvement invented by us.
A. The dies invented by us are applicable to all kinds of screw stocks
made for operating with two cutting dies which is a special merit of our
present Invention.
The improvement in the dies themselves consists in making the hollow
in which the screw threads are cut of a smaller bore than the diameter of
the spindle of the corresponding tap, and in cutting in the screw threads
with a master tap of a smaller diameter than the tap of the corresponding
bolt contrary to the usual mode by which this is done with a larger one.
In this manner the points (a, a,) become the cutting edges of the dies,
and remain so till the cutting of the screw on the bolt is finished (see
Figures 1 and 4). These cutting edges can be sharpened by grinding
the surfaces (a b, a b). These surfaces lie in a line with the radius of
the bolt when the cutting of the bolt is going to commence, and are of
course not square with the faces of the die, but slightly inclined towards
the same in order that the cutting edges may at once follow the course
of the thread.
A further improvement consists in employing threads in the dies of
greater depth, this increased depth being obtained by means of the above
mentioned master tap, the thread of which is deepened by a screwing
tool, the teeth of which have greater length than those of the standard
The purpose of deepening the thread in the dies is to give the
thread of the bolt which is being cut or screwed the exact depth required
at the time the same is finished, which on account of the cutting
screw.

page_text: surfaces (a b, a 6) then not lying any more in line with the radius of
the bolt would otherwise be impossible.
The novelty of this part of our improvement is,―
a. That the bore of the dies is made less than the diameter of the
spindle of the corresponding tap.
6. That the screw thread in the dies corresponds to a master tap of a
-smaller diameter than the regular tap belonging to that size of screws.
And c. That their threads have more height than the standard threads
of the corresponding bolt.
50
B. The improved tap is shown, Fig. 6 (Sheet I.); it exhibits tho
following particularities:-The screw-cutting part is preferred to be 5
times the diameter of the bolt. This part is nearly conical over its
whole length, the bottom of the threads being just visible at the lower
end of the tap and full sized at the upper end, and the middle of the
conical part over a length of three diameters of the bolt being slightly
diminished in size so that the sides of the conc represent a hollow line,
the depth of which hollow or departure from a straight line amounting
to about 1/8th part of the diameter of the bolt, the bottom of the grooves
between the ridges on this part of the tap being also turned deeper than
those at both ends. The cutting edges are formed by three or more
flutes over the length of the conical tap, the shape of which flutes does
not form part of this Invention. We prefer however as a general rule
three flutes each forming th of the circumference, and of a section of
half a circle. The ridges of the threads between the flutes are from the
cutting side backwards gradually and slightly diminished in height in
such a manner that the surface of the thread becomes part of an eccentric
circle. The cutting edges of the threads in the middle part of the tap
over a length of three diameters of the bolt are alternately or every
second one blunted in such a manner that only every other one or every
second one cuts. The tap after being hardened is then ready for use.
For this hardening the use of Martignoni's composition is preferred as it
enables the getting of a thoroughly hard surface, whilst the interior
remains soft and tough.

page_text: b. Having over the length of this hollow the grooves between the
threads deepened.
c. Having over the length of the same hollow every second or third
cutting edge of the ridges between the flutes blunted.
The following advantages are obtained by these improved dies and
|taps :—
•
a. They require less than one-half of the force which the usual form
needs, and as a consequence a smaller size of screw stock for the dies
can be used. For instance, screw stocks which will do for the old form
of th and 1, or for 3th to 1" can now be used respectively for the
to 1" and for 11th to to 13ths. In the same way bolts of for instance 1"
can be cut with these dies in a screw-cutting machine with the same
expenditure of power and with the same speed as bolts of the with
the old form of dies. It is the same with the wrenches for the taps.
b. The dies can be sharpened by simply grinding the radiating faces.
c. The threads in the bolts and nuts are really cut, bore shavings
coming off like those of a turning lathe, and the thread is not at all
forced in the metal as by the usual taps and dies, which have the fault
of increasing the diameter and the length of the bolt. By the use of
our taps and dies no such change in dimensions takes place.
d. The threads in the bolts and nuts are cut to the exact required
depth, and not partly so, as commonly. This is true to such an extent
that when the threads are turned away so as to leave their traces only
visible they will still act as threads.
e. In using these improved tools it is not necessary to turn them back-
wards and forwards in order to cut threads except just in the beginning
to get sufficient bite. After this the tools need only to be turned forward.
The bolts will be finished by running the screw stock only onece up and
down, and the nuts by running the tap only once through, all of which
results in a saving of half the time in labour in comparison with the old
tools.
f. Both dies and taps will last at least 5 times longer than the former
ones as the surfaces are thoroughly hardened and the centre remains
soft; further, they are not apt to break because they really cut the metal
and are not.subjected to undue strains,

page_text: g. No particular skill is required in the use of these tools nor particular
machinery for making them; any ordinary workman capable of making
the ordinary tools can make the improved ones.
3º. UNIVERSAL SCREW STOCK FOR CUTTING EITHER RIGHT-HANDED OR
LEFT-HANDED SCREW THREADS OF ALL POSSIBLE PITCHES AND ON !
ALL DIAMETERS OF BOLTS.
The following is an exact description of the same, reference being had
to Sheets II. and III. of the accompanying Sheets of Drawing:-
Sheet II. shows the tool as arranged for cutting screw threads on bolts
from /h up to the diameter, Fig. 1 representing a side view; Fig. 2, a 1
top view; Fig. 3, an end view; Fig. 4, a section over the line a, b; Fig. 5,
a section over the line c, d; and Fig. 6, a section over the line 6, a ; and
Figures 7 and 8 a modification of the guide block shown in the preceding
Figures; Fig. 7 being a side view and Fig. 8 a plan of same.
Sheet III. shows such a tool of larger size and arranged for cutting 1
screw threads on bolts of the up to 11th. In this Sheet a side view is
given in Fig. 1, a top view in Fig. 2; Fig. 3 represents an end view;
Fig. 4, a section over the line a, b; Fig. 5 shows the guide block and
the movable block with the turning tool taken out of the tool stock;
Fig. 6, the same guide block seen on top; and Fig. 7, a section through 2
the line c, d.
Figs. 8, 9, and 10 show a modification of the guide block shown in
the preceding Figures, Fig. 8 being a side view, Fig. 9 a front view, and
Fig. 10 a plan thereof. On both Sheets the same letters represent the
same parts.
2
In both these sizes of the tool in question, and in fact for all sizes
required, the cutting action is produced by two steel discs or wheels
marked A, having a tapered cutting edge on the circumference lying in
the same plane and turning on the axles B, which are carried by one
common box frame E. This box frame itself turns on a spindle C, by 3
means of which its position in reference to the axis of the bolt D to be
cut can be changed at pleasure. If the position of the box frame is at
right angles to the bolt the discs or wheels will produce on it when
pressed against them a circular incision the same as is effected by the
well known gas pipe cutter by means of one disc. When however the 3
box frame is set to a lesser angle than 90 degrees to the bolt, either to

page_text: the right or to the left, the result will be that a true screw line either
right or left handed and of any desired pitch will be cut in the aforesaid
bolt. For this purpose the spindle C of the box frame is furnished at
its furthest end with a worm wheel F, into which gears the endless
screw G moved by the hand wheel H, by which the exact inclination or
position of the discs in reference to the bolt to be screwed can be accu-
rately regulated at pleasure. The bolt to be out is inserted between the
guide block J and the two discs A.
In the smaller tools this guide block is made to advance, and thus to
press the bolt against the discs (see Sheet II.). This forward and
backward motion of the guide block J is accomplished by the hand
wheel N furnished with screw thread fitting on the pin of the guide
block, this hand wheel N being inserted between the end of the tool
stock L and the cover O, so that turning it round will cause the guide
block to advance or to retreat. The face of the guide block J is lined
with a material K which should be softer than the metal of the bolt to
be screwed in order not to damage the screw threads when cut. A kind
of hard white metal or hard brass is preferred for this purpose.
In the larger tools it is preferred to have this guide block J (see
Sheet III.) immovable in the direction of its length, seeing that it has to
be movable in a cross direction, as will be described presently. The
motion required for pressing the discs up against the bolt D is
accomplished by the frame P, which carries the spindle C of the box
frame E and which is movable on the tool stock L by a common slide
rest motion with the hand wheel M, as is shown clearly on Sheet III.
the
The screw lines or theads which the discs A when made of hardened steel
are capable of producing on iron bolts or steel taps are sufficiently deep for
bolts up to /t diameter; but for larger diameters of bolts it is preferred
to finish the threads or screw lines after being properly started with a
turning tool carried by the same tool stock (see Sheet III.). As soon
as a sufficiently deep bite for the threads has been obtained on the bolt,
the box frame E which carries thè discs is taken off its spindle C and
the block Q inserted instead. On this block Q is fixed a guide piece X
of brass, and before the bolt is cut any further, this guide piece X is
turned on the bolt by which operation the screw lines of the bolt
reproduce themselves on this piece and enable it to serve as a guide
for the further operation. This consists in inserting and gradually

page_text: .
advancing the turning tool R in the screw line and cutting with it the
bolt till it is finished. In order to adjust the turning tool R in the
screw line, a sideway motion can be given to the block J in the tool
. stock L by means of the screw S and the hand wheel Z, the threads
⚫ of the screw existing only in the block J and not in the tool stock L,
.whilst the screw S is kept in place by the ear Y. The forward and
backward motion of the turning tool R is shown in Fig. 5, being
produced by the hand wheel T which is screwed on the pin triveted to
the turning tool R, and which hand wheel T is kept in place by means
of the guide piece U and the cover O. Fig. 7 shows a section through
this guide piece U. The set screw V with the hand wheel W serves for
keeping the turning tool R tight during the operation of cutting. The
necessary slots are provided in the tool stock L to allow room for the
piece U and the set screw V, required when the guide block J is moved
sideways. Either with the smaller or with the larger tool the cutting
operation can be effected by grasping the bolt or tap to be cut in a vice,
and turning the tool by its handle around it; but by the large ones it
it preferred to fix the bolt or tap between the centres of a lathe, so that
it receives motion therefrom whilst the tool is kept free in hand, in such
a manner as to allow it to travel along the screw line of the bolt. The
larger tool can also be used for cutting square screw threads. For this
purpose an angular thread of the proper pitch is first cut, which is
afterwards enlarged by a properly formed turning tool inserted in the
guide block J; whilst two steel discs with a corresponding squared off
circumference are inserted in the box frame E and serve as guide in
order to keep the true screw line. On reference to Figs. 7 and 8,
Sheet II., it will be seen that we modify the guide block as above
described by the introduction of two small rollers running loose on
spindles, and having their axes parallel with the axis of the bolt to be
cut, and on reference to Figs. 8, 9, and 10, Sheet III., it will be seen
that the lower roller i is divided into two smaller rollers by the turning
tool R acting between them. The novelty lies in the use of two steel
discs formed as described above for producing screw lines on bolts and
taps, and of adjusting the position of these discs in reference to the bolt
in such a manner that right-handed or left-handed screws of any pitch
may be cut with them.

page_text: is not intended that it should replace the ordinary screwing gear, but
on the contrary complete it. With the possession of this tool every
maker of machinery can at once make any particular screws, either right
or left-handed, which he may be in want of, and for which he is not
provided with the proper ordinary gear. As for the corresponding nuts,
of course a tap has to be cut first and finished in the ordinary mode,
after which one is enabled to cut the nuts corresponding to the scrows.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Thieme Liernur, C. M. De Bruyn Kops,
and Johann Martignoni in the Great Seal Patent Office on the
31st October 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, CHARLES
THIEME LIERNUR, C. M. DE BRUYN KOPS, Civil Engineers, and JOHANN
MARTIGNONI, Mechanical Engineer, all of Frankfort-on-the-Maine, in the
Kingdom of Prussia, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventh day of May, in the year of our Lord
One thousand eight hundred and seventy-three, in the thirty-sixth year
of Her reign, did, for Herself, Her heirs and successors, give and grant-
unto us, the said Charles Thieme Liernur, C. M. De Bruyn Kops, and
Johann Martignoni, Her special licence that we, the said Charles Thieme
Liernur, C. M. De Bruyn Kops, and Johann Martignoni, our executors,
administrators, and assigns, or such others as we, the said Charles
Thieme Liernur, C. M. De Bruyn Kops, and Johann Martignoni, our
executors, administrators, and assigns, should at any time agree with,
and no others from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
SCREW-CUTTING GEAR," upon the condition (amongst others) that we, the
said Charles Thieme Licrnur, C. M. De Bruyn Kops, and Johann
Martignoni, our executors or administrators, by an instrument in writing
under our, or one of our, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and

page_text: with the two clips C and D (Figures 1, 2, and 3) turning on the
pivots P, and being held in place by the conical pins F. In taking out
these pins the clips C and D can be turned around by the ears ŉ on the
pivots P until brought into the position, shown by the dotted lines in
Fig. 1, for introducing or removing the dies, whilst the edges of the
clips C and D fit into the corresponding grooves of the dies, and keep
these firmly in position as soon as the clips C and D are fastened by the
conical pins F.
A modification of this improvement is shown in Fig. 4, representing
the face of the improved part of the screw stock, Fig. 5 being a section
of same through the line x, y. The square part for holding the dies
is in this instance furnished with only one movable clip, while the
opposite side has a fixed edge fitting in the corresponding groove of the
dies. The clip E turns on a pivot P, and is fastened with a conical
pin F, as before, and on being brought in the position shown by the
dotted lines the dies can be inserted or removed. These improved
forms of screw stocks are of course independent of the dies used, and the
peculiarity that any kind of dies belonging to a screw stock with two
dies can be used with them is a part of the present improvement
invented by us.

page_text: the cutting edges furthermore are made to stand radial to the objects to
be screwed, it is obvious that in these improved dies and taps the cutting
edges will cut on the iron in precisely the same way as a screwing tool is.
made to cut on a bolt in the lathe.
A. The dies invented by us are applicable to all kinds of screw stocks
made for operating with two cutting dies, and to all kinds of hand screw
cutting, and of screw-cutting machines made for operating either with a
solid die, with two dies, or with three dies (see Drawing, Sheet I.).
1°. The improvements in the double dies, either for screw stock or for
screw-cutting machine, consist in making the hollow into which the
screw threads are cut of a smaller bore than the diameter of the spindle
of the corresponding tap, and in cutting in the screw thread with a
master tap of a smaller diameter than the standard tap of the cor-
responding bolt. In this manner the points a, a, become the free
cutting edges of the dies and the only points which will touch the bolt,
and the screw threads will stand eccentrically to the surface of the bolt.
till the cutting of the screw is finished (see Figures 1 and 4). These
cutting edges can be sharpened by grinding the surfaces a, b, a, b. These
surfaces lie in a line with the radius of the bolt when the cutting is going
to commence, and are not squared with the faces of the dies but inclined
towards the same, in order that the cutting edges may at once follow the
course of the thread.
2°. The solid die (Sheet I., Fig. 7). In order to adapt this same
improvement to a solid die, and to obtain the eccentricity of the screw
threads of the die to the surfaces to be cut, the tap hole is screwed with 2
a master tap of a diameter by about the depth of the thread larger than
the standard tap, and the cutting points a, a, are forced inwards towards
the centre in order that they may become the free cutting edges. To
this end at equal distances at the circumference three or more holes c
are bored of about 1 or ½ of the diameter of the tap leaving about 1/16
to 1 of an inch of metal between these holes and the tap hole. We
prefer three holes, but four or more may be employed should such be
required. The remaining ridges between these small holes and the' tap
hole are cut away following the lines a, b, and d, e, and a tapered steel
tool inserted between the edges a, b, and d, e, the die being in a red hot 3
state, which by a few blows will force the points a, a, out of the true
circle towards the centre. These points a are to be equalised by a

page_text: standard tap of the required size, and the receding edges of the die a, e¹,
cut away in the way as shown in the Figure. The face of the die in
which the bolts have to enter is tapered away in the usual way, and the
die after being liardened is ready for use. When the points a get dull
by long use they can be re-sharpened by filing the edges a, b, after the
-die having first been softened. When the dio gets too large the operation
of forcing the points a inwards as described above can be repeated till
the die gets worn out beyond repair.
3°. The triple die (Sheet I., Figures 8 and 9). To adapt this samo
improvement to the triple die we prefer to make the slots in the die
stock in such a way that the lines a, a³, of the cutting edges of the dies
shall run radial to the bolt to be cut (see Fig. 9), or if for one cause or
the other it is preferred to have this line a, a¹, parallel with the radius
instead of coincident with it (see Fig, 9), then we make only the last
part of the cutting edge a, c, radial to the bolt to be cut. After the
blank dies have been fitted in the slots and signed 1, 2, and 3, corres-
ponding to the same signs in the slots, they are put in the corresponding
slots of a special die holder which serves only for the purpose of tapping
the dies. In this special die holder the slots are made of the exact size
of those in the stock, but at a different inclination towards the centre, as
shown by the dotted lines a, c, b, b. At the outer ends of these slots
there may be set screws or any other contrivance to push the dies
forwards to the centre, or for pulling them in and out. In this special
die holder the dies are cut with a master tap, either of a smaller, a right
sized, cr a larger diameter than the standard tap, a master tap of a
larger diameter being preferred by us, and after they have been finished
and hardened and replaced in the working die-stock, it is obvious that
the screw threads of the dies will stand eccentrically to the surface to be
cut in such a way that only the points a will cut.. At the face of the
dies where the bolts have to enter, the 2 or 3 first threads are tapered
away, in order that the bolt may take at once the lead of the thread,
and the bolt can now be cut at one downward stroke, if at least the
tool is arranged for withdrawing the dics at once at the end of the
cutting.
:
:
3. We therefore claim as of our Invention making the dies so that their
screw threads shall always stand eccentrically on the surfaces to be cut,
the cutting edges being the only points that touch the objects to be cut,
~ shows ant fouth

page_text: B. The improved tap is shown Fig. 6 (Sheet I.); it exhibits the
following particularities:-The screw cutting part is preferred to be 5
times the diameter of the bolt. This part is nearly conical over its
whole length, the bottom of the threads being just visible at the lower
end of the tap, and full sized at the upper end, and the middle of the
conical part over a length of three diameters of the bolt being slightly
diminished in size, so that the sides of the cone represent a hollow line,
the depth of which hollow or departure from a straight line amounting
to about 10 part of the diameter of the bolt, the bottom of the grooves
between the ridges on this part of the tap being also turned deeper than 1
those at both ends. The cutting edges are formed by three or more
flutes over the length of the conical tap, the shape of which flutes does
not form part of this Invention. We prefer, however, as a general rule
three flutes, each forming ½ of the circumference, and of a section of
half a circle. The ridges of the threads between the flutes are from the 1
cutting side backwards gradually and slightly diminished in height, in
such a manner that the surface of the thread becomes part of an
eccentric circle. The cutting edges of the threads in the middle part of
the tap over a length of three diameters of the bolt are alternately, or
every second one, blunted in such a manner that only every other one or 2
every second one cuts. The tap after being hardened is then ready
for use.

page_text: 1", and for 1" to 1". In the same way bolts of, for instance, 1″ can
be cut with these dies in a screw-cutting machine with the same expen-
diture of power, and with the same speed as bolts of " with the old
form of dies; it is the same with the wrenches for the taps.
b. The dies can be sharpened by simply grinding the radiating
faces.
c. The threads in the bolts and nuts are really cut, bore shavings
coming off like those of a turning lathe, and the thread is not at all
forced in the metal as by the usual taps and dies, which have the fault
of increasing the diameter and the length of the bolt. By the use of
our taps and dies no such change in dimensions takes place.
d. The threads in the bolts and nuts are cut to the exact required
depth, and not partly so, as commonly. This is true to such an extent
that when the threads are turned away so as to leave their traces only
visible they will still act as threads.
e. In using these improved tools it is not necessary to turn them
backwards and forwards in order to cut threads, except just in the
beginning to get sufficient bite; after this the tools need only to be
turned forward. The bolts will be finished by running the screw stock
only once up and down, and the nuts by running the tap only once
through, all of which results in a saving of half the time in labor in
comparison with the old tools.
f. Both dies and taps will last at least five times longer than tho
former ones, as the surfaces are thoroughly hardened, and the centre
remains soft; further they are not apt to break, because they really cut.
the metal and are not subjected to undue strains.
g. No particular skill is required in the use of these tools, nor par-
ticular machinery for making them; any ordinary workman capable of
making the ordinary tools can make the improved ones.
3º. UNIVERSAL SCREW STOCK FOR CUTTING EITHER RIGHT-HANDED OR
LEFT-HANDED SCREW THREADS OF ALL POSSIBLE PITCHES AND ON
ALL DIAMETERS OF BOLTS.
The following is an exact description of the same, reference being had
1
TT
Shouts of Dimminm

page_text: Figures 1 to 6, inclusive, show the tool as arranged for cutting screw
threads on bolts from " up to 5" diameter, Fig. 1 representing a
side view; Fig. 2, a top view; Fig. 3, an end view; Fig. 4, a section
over the line a, b; Fig. 5, a section over the line c, d; and Fig. 6, a
section over the line b, a.
E
Figures 7 to 13 show such a tool of larger. size, and arranged for
cutting screw. threads on bolts of up to 1"; Fig. 7 being a side
view; Fig. 8, a top view; Fig. 9, an end view; Fig. 10, a section over
the line a, b. Fig. 11 shows the guide block and the movable block
with the turning tool taken out of the tool stock; Fig. 12, the same 1
guide block seen on top; and Fig. 13, a section through the line c, d.
Similar letters of reference indicate similar parts in each of the
Figures respectively.
In both these sizes of the tool in question, and in fact for all sizes
required, the cutting action is produced by two steel discs or wheels 1
marked A, having a tapered cutting edge on the circumference, lying in
the same plane and turning on the axle B, which are carried by one
common box frame E. This box frame itself turns on a spindle C, by
means of which its position, in reference to the axis of the bolt D to be
cut, can be changed at pleasure. If the position of the box frame is at 2
right angles to the bolt, the discs or wheels will produce on it, when
pressed against them, a circular incision, the same as is effected by the
well-known gas pipe cutter, by means of one disc. When, however, the
box frame is set to a lesser angle than 90 degrees to the bolt, either to
the right or to the left, the result will be that a true screw line, 2
either right or left handed, and of any desired pitch, will be cut in the
aforesaid bolt. For this purpose the spindle C of the box frame is
furnished at its furthest end with a worm wheel F, into which gears the
endless screw G moved by the hand wheel H, by which the exact
inclination or position of the discs, in reference to the bolt to be screwed, 3
can be accurately regulated at pleasure. The bolt to be cut is inserted
between the guide block J and the two discs A.
In the smaller tools this guide block is made to advance, and thus to
press the bolt against the discs (see Figures 1 to 6). This forward and back-
ward motion of the guide block J is accomplished by the hand wheel N 3

page_text: furnished with screw thread fitting on the pin of the guide block, this
hand wheel N being inserted between the end of the tool stock L and
the cover O, so that turning it round will cause the guide block to
advance or to retreat. The face of the guide block J is lined with a
material K, which should be softer than the metal of the bolt to be
screwed, in order not to damage the screw threads when cut. A kind of
hard white metal or hard brass is preferred for this purpose.
In the larger tools it is preferred to have this guide block J (see
Figures 7 and 8) immovable in the direction of its length, seeing that
) it has to be movable in a cross direction, as will be described hereafter.
The motion required for pressing the discs up against the bolt D is
accomplished by the frame P, which carries the spindle C of the box
frame E, and which is movable on the tool-stock L by a common slide
rest motion with the hand wheel M, as is shown clearly in Figures 7, 8,
and 10.
The screw lines or threads, which the discs A when made of hardened
steel are capable of producing on iron bolts or steel taps, are sufficiently
deep for bolts up to 5" diameter, but for larger diameters of bolts it is
preferred to finish the threads or screw lines after being properly started
) with a turning tool carried by the same fool-stock (see Figures 7, 8,
and 11). As soon as a sufficiently deep bite for the threads has been
obtained on the bolt the box frame E, which carries the discs, is taken
off its spindle C, and the block Q inserted instead (see Figures 11
and 12). On this block Q is fixed a guide piece ✗ of brass, and before
the bolt is cut any further this guide piece X is turned on the bolt, by
which operation the screw lines of the bolt reproduce themselves on this
piece and enable it to serve as a guide for the further operation. This
consists in inserting and gradually advancing the turning tool R in the
screw line, and cutting with it the bolt till it is finished.
In order to adjust the turning tool R in the screw line a sideway
motion can be given to the block J in the tool-stock L, by means of the
screw S and the hand wheel Z, the threads of the screw existing only
in the block J and not in the tool-stock L, whilst the screw S is kept
in place by the ear Y (see Figures 7, 8, and 11). The forward and
backward motion of the turning tool R is shown in Fig. 11, being
produced by the hand wheel T, which is screwed on the pin t riveted
B

page_text: to the turning tool R, and which hand wheel T is kept in place by means
of the guide piece U and the cover O. Fig. 13 shows a section
through this guide piece U. The set screw V with the hand wheel W
serves for keeping the turning tool R tight during the operation of
cutting. The necessary, slots are provided in the tool-stock L to allow 5
room for the piece U and the set screw V, required when the guide
block J is moved sideways. Either with the smaller or with the larger
tool the cutting operation can be effected by grasping the bolt or tap to
be cut in a vice, and turning the tool by its handle around it, but by
the large ones it is preferred to fix the bolt or tap between the centres 1
of a lathe, so that it receives motion therefrom, whilst the tool is kept
free in hand in such a manner as to allow it to travel along the screw
line of the bolt. The larger tool can also be used for cutting square
screw threads. For this purpose an angular thread of the proper pitch
is first cut, which is afterwards enlarged by a properly formed turning 1
tool inserted in the guide block J, whilst two steel discs with a corre-
sponding squared off circumference are inserted in the box frame E, and
serve as guide in order to keep the true screw line.
On reference to Figures 14 and 15, Sheet II., it will be seen that we
modify the guide block as above described by the introduction of two 2
'small rollers running lose on spindles and having their axes parallel
with the axis of the bolt to be cut; and on reference to Figures 16, 17,
and 18, Sheet II, it will be seen that the lower roller is divided into
two smaller rollers by the turning tool R acting between them.
We claim in this part of our Invention the use of two steel discs 2
formed as above described for producing screw lines on bolts and taps,
and the adjustment of the position of these discs in reference to the bolts
in such a manner that right-handed or left-handed screws of any pitch
may be cut with them.
This part of our Invention presents a new mode of cutting screws,
having the great advantage of readily producing screws of any dimensions.
It is not intended that it should replace the ordinary screwing gear, but
on the contrary complete it. With the possession of this tool every
maker of machinery can at once make any particular screw either right
´or left-handed, which he may be in want of, and for the making of
which he is not provided with the proper ordinary gear. As for the

page_text: corresponding nuts of course a tap must first be cut and finished in the
ordinary mode, and then the nuts corresponding to the screws.
In witness whereof, I, the said C. M. De Bruyn Kops, have
hereunto set my hand and seal, this Twenty-seventh day of
October, in the year of our Lord One thousand eight hundred
and seventy-three.