IMPROVEMENTS IN MACHINES FOR CUTTING SCREW THREADS
Year: 1880

page_text: LETTERS PATENT to Alfred Julius Boult, Patent Agent, of 323, High Holborn,
in the County of Middlesex, England, for an Invention of "IMPROVEMENTS IN
MACHINES FOR CUTTING SCREW THREADS." A communication from abroad by
Frank Armstrong, of Bridgeport, in the State of Connecticut, and United States
of North America.
COMPLETE SPECIFICATION filed by the said Alfred Julius Boult at the Office
of the Commissioners of Patents on the 7th April 1880.
ALFRED JULIUS BOULT, Patent Agent, of 323, High Holborn, in the County of
Middlesex, England. "IMPROVEMENTS IN MACHINES FOR CUTTING SCREW THREADS."
A communication from abroad by Frank Armstrong, of Bridgeport, in the State of
Connecticut, and United States of North America.
My Invention relates to certain improvements in machines for cutting screw
threads, and more particularly to cutting the threads in dies intended for cutting
threads on the ends of pipes, in which a double taper is given to the threads.
Prior to my Invention the only way in which a double taper thread could be cut in
a die plate has been by tapping with two different tapered dies, which involves
considerable labor, time, and care. The object of my Invention is to produce a
machine by which a double taper thread may be cut automatically with a rotary
cutter, and with this end in view my Invention consists in the peculiar construction
and arrangement of mechanism hereinafter described, whereby I am enabled to cut
threads of a different taper with a rotary cutter. In order that those skilled may
know how to make and use my improved machine, I will proceed to describe its
construction and operation, referring by letters to the accompanying Drawings, in
which Fig. 1 is a front view of a machine embodying my Invention; Fig. 2 is a
plan or top view of the same; Fig. 3 is a side clevation looking in the direction of
the arrow at Fig. 2, and only up to the dotted line; Fig. 4 is a vertical section
through the carriage at the line X, X, Figure 2. Fig. 5 is a front view of the die
chuck with a pair of dies which have been duly cut arranged therein.
Fig. 6 is a rear view of the tool arbor and its support. Similar letters indicate
like parts in the several Figures. A is the bed of the machine, and B, B, suitable
ordinary bearings for the rotary shaft C, to which is secured in the ordinary manner
the chuck D. E is the drive shaft, from which, by pulleys F, F, and belts G, G, or
in any other suitable manner, form and motion is applied to the pulleys H, H, en

page_text: the shaft C through a shifting clutch I, which is operated by any suitable shifting
dovice K. L is a drive pulley on the shaft E, and from which rotary motion is
communicated through a belt M and suitable tightening device N to the rear end
of a rotary tool holder O arranged in an arbor P, and held therein by the pulley Q
and collar R. S is a removable rotary cutter secured to the tool holder O by a screw
a' in the ordinary manner. The arbor P is formed with a vertical circular projec-
tion T which is pivoted at its centre with a screw-bolt b, so as to be capable of
rotary adjustment thereon, a segmental slot c and set-screw d permitting such
movement and providing a means for fixing it in any given adjustment, as will be
more fully explained hereinafter. This projection T is pivoted as described to an
horizontal cylindrical arm U projecting rearward from a hollow cylinder or head V
split on one side at e, and provided with a tightening screw-bolt f. This hollow
cylinder or head is arranged over and around a solid cylindrical post W secured to
or formed with a bed-plate X. A central hole or channel Y is formed in the post.
W, and a screw-nut and plate Z is secured in position over the top thereof, and in
which runs a screw-bolt A' arranged centrally within a collar B' in the top of the
cylinder head V, so that the lathe may be raised and lowered, and with it the arbor
P, a screw-bolt g, the point of which lies in a vertical channel in the post, preventing
any rotary motion of the cylindrical head (see Fig. 3). Any wear between the
cylinder head and the post is taken up by the tightening screw f. The bed-plate
or carriage X travels on dove-tail ways C', C, arranged longitudinally on the
transversely movable carriage D' arranged with dove-tail slides on the bed A of the
machine. On the top front edge of the carriage D' is secured or formed a bar or
plate E, through which passes a long screw E, the front end passing through a
yoko G¹, and provided with a hand wheel H. The rear end of this screw passes
loosely through another yoke I' arranged at the rear end of the carriage D'. The
threads of the screw travel in a threaded hanger or nut h (Fig. 4) arranged on the
underside of the plate or arbor carriage X, and consequently the rotation of the
screw will cause the carriage and arbor referred to to travel back and forth; this
movement is limited by the two cheek-nuts K, K', arranged each side of the yoke
G¹ on the threaded end of a side-bar L' which passes through a bracket bearing M'
on the side of the carriage X, and through a bearing in the rear yoke 1'. The
carriage X may be held against reciprocation by screws i and k, or either of them
(see Fig. 3). On the opposite side of the carriage X a push-bar N' is arranged with
its front end fixed in the yoke G₁ and its rear end passing through a sleeve bearing
or guide O' (arranged on rear yoke 1), and provided with a head P¹, between
which and a suitable annular shoulder in the guide O' is arranged a spring Q, the
effect of which is to draw the carriage X rearward. This head P is furnished with
an antifriction wheel or pulley R' (see Fig. 3) which travels over a former, shown
in dotted lines, within a box or frame S' arranged on a cross-bar T' at the rear of
the machine. This former may be made in any design and of one or more parts,
and adjusted by set-screws 1, 2, and as the carriage D₁ is fed towards the chuck D,
in the manner presently explained, the rotary cutter S will be moved back and forth
to the extent of the profile of the "former." The carriago D', as before stated, is
arranged on dove-tail ways U' (see Fig. 3), and is caused to travel toward or from the
chuck D by a feed screw V passing through a screw-nut or hanger W on the under-
side of the carriage. One end of the feed-screw has its bearing in a collar-bracket
X', and the other end in a bracket Y', and is held against longitudinal movement by
a collar L: This feed-screw and the chuck are operated by a system of gears 1, 2, 3,
such as are usually employed on an engine-lathe, and by which the feed of the carriage
D' and the speed of the chuck may be regulated to cut any number of threads wanted.
I have shown the clutch I as operated from a rock-shaft by a bell-crank lover K,
the horizontal arm of which may be automatically lifted to shift the clutch by a
wedge or incline m secured to the carriage D', but any other means may be used
to accomplish this result.
As this machine is particularly designed to make screw-cutting dies with one or
more tapers I have shown the blanks properly secured in position within a suitable

page_text: holder n arranged on tho chuck. The blanks o, o, are held in any given position
by screws p, p, the diameters of which are sufficiently smaller than the holes in
the blanks through which they pass, to permit of the required or necessary longi-
tudinal adjustment which is produced by the screws g. 9, in the heads or ends of
the holder n; each end of the holder is numbered or otherwise marked in accordance
with marks on the die-blanks, so that every successive pair operated upon can be
arranged in the holder, so that the cutter will begin its work exactly at the same
place, whereby each half of a die is always interchangeable with the corresponding
half of any other one. Any other suitable or obviously other marks necessary may
be employed to regulate and determine the adjustment of the blanks with the
screws q, q. Having described the construction and arrangement of the several
parts of my improved machine, I will now proceed to describe its operation :-The
usual parts being properly adjusted and geared, and the blanks arranged in the
chuck with the clutch locked with right hand pulley H', and the formers adjusted
in the form box S'; the machine is started and the rotary cutter is driven towards
the left by the system of belts and pulleys, and at the same time the feed screw V'
causing the carriage D¹ to travel towards the chuck; the cutter is brought
gradually to work upon the blanks, the axis of motion of the cutter being changed
according to the profile of the "former," the inclination or taper of the thread being
cut is correspondingly changed. This movement of the arbor carriage X is induced
by the push-bar N, yoke G', and screw F¹ connected as described. In order to
prevent the mutilation of the threads by the rotary cutter, which would necessarily
occur if the axis of the tool were coincident or parallel with the axis of the chuck.
The tool arbor F is rotated upon the pivot screw b (see Fig. 6) below a horizontal
plane to cut a right hand, and above to cut a left hand thread, and it is secured in
either proper position by tightening the screw d. When the cutter has finished its
work the incline has lifted the horizontal end of the bell-crunk lever K of the
shifting device and caused the clutch to move between the pulleys H, H, leaving
them both free to rotate on their shaft without rotating the chuck D or causing any
further movement of the carriage D', hence the cutter will simply revolve without
doing any work. This being observed by the attendant he moves the cutter to the
exact centre (or so that it will be free to travel back without touching the threads
it has cut) by turning the hand-wheel H¹ until the yoke G¹ comes in contact with
the cheek-nut K¹, when the clutch I is shifted towards and in contact with the
outside pulley H, when the motion of the shaft C is reversed and the carriage D'
run back to the position from which it started, and it will be understood that when
the cutter next approaches the chuck it will be in exactly the same manner as the
preceding time, and hence it follows that if the No. 1 half of the dic-blank is put
in its correspondingly numbered end of the holder n, and No. 2 half of blank in
No. 2 end of holder, that the cutter will begin its work at precisely the same point
where it began on the previous operation, and hence if this rule is followed every
half of a screw-cutting die made by machine will be interchangeable with another
correspondingly half, so that should one-half of a die become broken it can be
readily replaced. This I consider a very important result in the use of my machine.
While my present machine, as illustrated in the Drawings, is designed for making
Screw-cutting dies, it will be observed that it can be used with great facility to cut
threads on bolts or screws by properly securing the blanks within a chuck and
altering the forms in the form-box S¹; in fact the rotary cutter may be made to
cut any profile inside or out according to the profile of the form, and made more
expeditiously and with less wear to the tool than is the case with a stationary tool
or chaser according to the number of cutting points on the rotary, as the work is
divided among the said cutting points.
Having now described my Invention and the manner in which the same may be
carried into practical effect, I would have it understood that I do not wish to be
confined to the exact details of constructions, as they may be varied in many
particulars without departing from the spirit of my Invention, the essential feature
of which lies in so arranging and combining a rotary cutter with a revolving chuck

page_text: and former that a screw thread of one or more tapers or a profile may be cut there-
with; but what I do claim is,-
1st. In a machine for cutting screw-threads the combination of a rotary spindle
and chuck D and carriage D¹, connected by gears and screw-feed, as described; a
rotary cutter secured to an arbor, adapted to be adjusted in the manner described;
a former-box and former, all combined, constructed, and operated as hereinbefore
set forth.
2d. The carriage X mounted on the carriage D¹ in combination with the
yokes G', plates E and T', side-bar L', push-bar N₁, screw F, spring Q', head P',
and adjustable formers, all arranged to operate in the manner set forth.
3. The arbor P adjustably secured to an extension U of split cylinder V, the
latter having a vertical adjustment upon a cylindrical post W on carriage X, sub-
stantially and for the purpose set förth.
-
4th. The arbor P mounted as described upon a carriage, and adapted to-be
adjusted toward the front and back of the inachine by the screw F¹, in the manner
described and for the purpose set forth.
5th. The rotary cutter arranged upon an arbor adapted to be rotated and adjusted
in a plane parallel with the axis of motion, whereby the pitch of the thread is
regulated, as herein before set forth.
6th. The cylinder V split at 2 and provided with tightening screw f, substantially
and for the purposes hereinbefore set forth.
7th. The combination and arrangement with the carriage X, push-bar N¹,
yoke G, and plates E' and T' of the side-bar L and cheek-nuts K, K¹, substantially
as and for the purpose. set forth.
8th. The form-box or frame S provided with suitable formers and adjusting
devices, substantially as and for the purpose set forth.
9th. The die-blank holder won the chuck provided with numbers or other
characters conforming to the two halves of the blank, substantially as and for the
purpose described.
In witness whereof, I, the said Alfred Julius Boult, have hereto set my hand
and seal, this Seventh day of April, in the year of our Lord One thousand
eight hundred and eighty.
ALFRED JULIUS BOULT. (LS)