Improvements in connection with Dies for Cutting Screw Threads.
Year: 1898

page_text: Date of Application, 21st Dec., 1898-Accepted, 16th Sept., 1899
COMPLETE SPECIFICATION.
Improvements in connection with Dies for Cutting Screw Threads.
We, OTTO QUANDT, of 1, Blucher Strasse, Berlin, in the Empire of Germany,
Engineer, and WENZEL SCHELBECK, of 127, Alexandrinen Strasse, Berlin, afore-
said, Engineer, 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:-
In connection with dies for cutting screw threads, where, after the screws have
been finished, the cutting cheeks separate automatically, interruptions very fre-
quently occur in the working, owing to the cutting cheeks getting jammed, by
reason of the chips, etcetera; the strength of the spring, which is to force the
cheeks asunder, not being sufficient to accomplish this object. This refusal of the
appliance to work, most frequently occurs when the bolts to be operated upon are
somewhat thicker than was intended.
The improvements forming the subject of the present invention, is to remedy
the above-mentioned defects.
In the annexed drawing which illustrates the invention, Figure 1 shews the
die in longitudinal section; Figure 2 shews the top part as seen from the inside;
Figure 3 shews the adjustable ring seen from the inside; Figure 4 shews the
carrying disc from the inside; and Figure 5 shews a view of the apparatus, after
the screw has been completed.
The shaft c is provided with socket-shaped thick parts a b, and by its means
the thread-cutting die is connected with the revolver head of the machine or
lathe. In the bore of this shaft c there lies a spiral spring d, the back end of
which rests (at the right hand in the drawings) in the revolver head or support,
and the forward head of which (left, in the drawings) rests against a pin provided
in the bore. A bolt e, provided with a screw head at one end, passes through the
entire bore of the shaft c, and through the spiral spring d resting in same; and
its other end, provided with a screw thread, reaches to the bore of the shaft where
it widens over the piece attached to the carrying disc. This widened bore f of
the shaft serves for receiving the part g attached to the carrying disc h, into the
back end of which-provided with a female screw thread, the front end of the
bolt e is screwed; so that although the carrying disc is firmly connected with the
shaft, if the force with which the carrying disc presses the spiral spring dis
increased, and the spiral spring compressed, the carrying disc may get out of
connection with the shaft. The carrying disc h is provided with a narrow rim i,
which is cut out at j.
In the centre of the carrying disc, a concentric cavity k is arranged for the
purpose of receiving a spring m. In the carrying disc, three screw holes n are
provided, and also an arc-shaped opening o. The carrying disc, furthermore, at
its side carries a double lever q, turnable on a pin p, the one end of which is
shorter than the other.
On one side of the socket a of shaft c, there is a pin s, and on the other side
a nipple a². On the carrying disc the top part t fits, and in the latter rest the
cutting cheeks u, which are movable in a radial direction.
The profile of the three groove shaped incisions v, arranged in a radial direction

page_text: in the top part t, is cruciform, as will be seen from Figure 5. The groove w of
the cutting cheek u corresponds to the upper narrow part of the incision, the
lower thicker part corresponds to the wider portion of the incision v, and the
lower narrow addition w¹ corresponds to the groove w² arranged at the bottom of
the incision. The front ends of the cutting cheeks are provided in the customary
manner, with sharp cutters for cutting the screw threads, which, however, are
not formed in the same manner as in connection with the cutting cheeks hitherto
in use, but have an undercut edge ', so that the cutting cheeks not only grasp
sharply; but may also be opened without damaging the screw thread. In the
under addition wl of the cutting cheeks, an incision w³ is provided, in which the
adjustable ring z rests.
The outer rim of the top part t has a turned off edge i¹, corresponding with the
rim of the carrying disc h, so that the carrying disc and the top part fit well
together. Round the central bore of the top part there is a narrow edge t²,
(Figure 2) towards the bottom, the height of which corresponds to the depth of
the cavity in the carrying disc h. In the annular groove t¹ the adjustable ring
is so placed that the narrow part ¹, of the ring rests in the incisions w³ of the
addition of the cutting cheeks. The adjustable ring is provided with a
thumb A, of which an incised part A' rests in the incision of the top part, so
that the adjustable ring may be moved to a certain extent, from the outside.
Part of the adjustable ring is provided with three incisions 2223, both at the
inner edge and at the outer edge, which produce the adjustment of the cutting
checks. The side of the ring z turned towards the shaft carries a pin which
passes through the opening o in the carrying disc h. Corresponding to holes n
in the carrying disc h, there are also holes provided in the top part through
which the top part and carrying disc are firmly joined together by means of
screws. Round the part 2 of the top part, a spring m is placed, one end of which
catches into a hole in the top part t, and the other end of which catches into a
hole in the adjustable ring. The spring m rests in the cavity k of the carrying
disc h.
It still remains to be mentioned that on the side of the carrying disc h, bearing
against a socket a, a short pin h¹ is provided, which catches into a corresponding
hole in socket a. The length of the pin corresponds exactly to the length of
that part of pin which passes through the opening o in the carrying disc.
The appliance works in the following manner;
When the disc has been fixed to the turning lathe on the revolver head of the
engine, by means of the shaft c, the bolts to be screwed are inserted between the
cutting cheeks. By moving the thumb A, the adjustable ring z is moved, and by
means of the incisions it moves the cutting cheeks u inwards, so that they seize
the bolt. By moving the adjustable ring 2, the spring m is contracted, so that it
will continually be endeavouring to press the adjustable ring back into its
original position, which, however, does not take place, because pin rests
behind the nipple a² of the socket a. When the bolt has been threaded to the
required length, the bolt draws the die slightly away from the socket, because the
shafte is retained from further forward movement through the edge bearing against
the contact in the well known manner, so that, as the pin is now released, the
spring m may exercise its effect, draw back the adjustable ring, and open the
cutting cheeks. This effect will, however, very frequently not be produced, as
the strength of the spring is not sufficient to surmount the resistance of the
chips which have got fixed in the thread. The die, therefore, independently of the
socket which remains fixed, participates in the further revolutions of the bolt
until the shorter arm of the double armed lever q strikes against the pin s,
whereupon the larger arm of the lever strikes against the thumb A, and carries
back the adjustable ring into its original position, so that the cutting cheeks are
opened.
The appliance may also be made in such a manner that the bolt is fixed whilst
the die revolves.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed; we declare that what
we claim is:
1. In a die for cutting screw threads with radially movable cutters, a double
ring (2) adapted to be actuated by means of a lever or handle (A), and the lower
ring of which has incisions (223) both on its inner and its outer edges, and which
ring is carried back into its original position by means of a spring; substantially
as and for the purposes set forth.
2. A screw cutting die having its main parts arranged and adapted to operate
substantially as herein set forth with reference to and shewn in the drawings.
3. In a die of this character for cutting screw threads of the character
specified, a double lever g, on the side of the carrying disc (h), adapted when
the top part of the carrying disc turns to strike a stop pin on the socket (a) where-
by the handle A and hence, also the double adjustable ring z are displaced; sub-
stantially as and for the purposes set forth.
4. In a screw cutting die of the character described, the bolt (e) screwed into
the part (g) connected with the carrying disc (h), said bolt (by means of its head)
serving as a counterpoise for a spiral spring (d) which rests on the shaft (c).
whereby the top part (t) and carrying disc (b), on the one part, are connected
with the shaft (c), on the other part, in such a manner that the top part and
carrying disc cannot be drawn away from the shaft (c), until the resistance of the
spiral spring has been overcome; substantially as set forth.
5. The combination and arrangement of parts constituting the screw cutting
die; particularly as shown in and set forth with reference to the drawings.
Dated the 20th day of December 1898.
CHEESBROUGH & ROYSTON,
Applicant's Patent Agents, 15, Water Street, Liverpool.