Improvements in Dies for Rolling Screw-threads.
Year: 1893

page_text: Date of Application, 5th Dec., 1893-Accepted, 20th Jan., 1894
Improvements in Dies for Rolling Screw-threads.
I WILLIAM OSCAR BEMENT, of 18 Tirrell Street Worcester, in the County
of Worcester, and State of Massachusetts, United States of America, Iron Worker,
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:
My invention relates to dies for forming screw threads by rolling the blanks to be
threaded between dies, which can be adapted to produce either a straight or a
gimlet-pointed thread, as may be desired.
In the drawings,
Figure 1 represents one of my improved dies showing a plan view of the working
face of the die, which is curved at its lower side, being designed to roll a gimlet-
pointed thread, and hence, conforms to the shape of the blank; the heavy lines
indicate the spaces between the ribs, and the unshaded lines indicate the ribs which
form the thread. The entering end of the die is at the bottom of the sheet.
Figure 2 is a sectional view of the two dies, through the line 1—1, Fig. 1.
Figure 3 is a sectional view through the line 2-2, Fig. 1.
Figure 4 is a sectional view through the line 3-3, Fig. 1.
Figure 5 is a sectional view through the line 4-4, Figure 1.
Figure 6 represents the blank at the point of action, of the dies, shown in
Figure 2, and similarly,
Figures 7, 8 and 9 represent the blank at the points of action of the dies, shown
in Figs. 3, 4 and 5, in which will be noticed a gradual development of the thread
from the root to the point. The shape of the dies in cross-section, and the
progressive development of the thread at four several stages of the operation is
thus clearly illustrated.
Figure 10 is also a plan of the working face of one die showing a smaller number
of ribs with which the threading may be done. The entering end of the die is at
the left of the sheet.
Figures 11, 12 and 13 show the dies in cross-section at the three points, 5, 5, 6, 6, 7, 7,
Fig. 10.
Figure 14 is a plan view of a die with a flat face, designed to thread a blank
with a straight surface, the entering end of the die being at the left of the sheet.
Figures 15, 16 and 17 are sectional views of this die, and its mate at the
points 8, 8, 9, 9, 10, 10.
The faces of the dies shown in Figs. 1 and 10, are necessarily curved along their
lower sides as they are designed to produce gimlet-pointed screws, as illustrated in
the several sectional views of the dies shown in connection with those figures.
Upon turning to Figs. 1, 10 and 14, it will be noticed that each of the ribs, or
raised portions of the die, which run across its face, and which are designated by
the unshaded portions, 11, 12, 13 &c. is substantially of the same width from end
to end.
It will also be noticed that all the ribs which start from the entering end of the
die are so cut that their tops are sharp.
This is shown in Fig. 2, and in the corresponding Figs. 11 and 15, in connection
with the other face views of the dies, Figs. 10 and 11.
The effect upon the blank is clearly shown in Fig. 6, where the body of the blank
is sharply scored, but at this stage, the point of the blank is not threaded.
As soon as the ribs begin to run from the side of the die, 19, 20, 21, 22, 23, &c.

page_text: they increase somewhat in width, each being a little broader than the preceding
one, until the ribs are wide enough to produce the desired thread when the width
becomes uniform.
This is shown in the sectional views in Figs. 3, 4 and 5, and the progressive
formation of the thread is illustrated at corresponding points in the process in
Figs. 7, 8, and 9. The distinguishing feature of my form of die being that the
thread is gradually developed from the rcot to the point of the blank, every
working rib essential to the process beginning at the base of the thread and acting
throughout its entire length.
It will be noticed that in Fig. 7, the thread is already perfect at the top, while
still only partially developed at the lower portion.
In Fig. 8, there is a still further progress as the wide ribs act upon the lower
parts of the screw, while in Fig. 9, the thread is completed throughout its entire
length.
While I prefer to have several sharp cutting ribs at the entering end of the die,
in order that the body of the blank may, at the outset, be scored throughout the
length of the thread as shown in Figs. 1 and 2, and in the view of the blank
shown in Fig. 6, this is not essential to the successful operation of my improved
dies, for I can dispense with all but one of the sharp ribs and only need to use a
succession of ribs of increasing width sufficient to secure the full development of
the thread.
This is illustrated in Fig. 10, which shows the working face of one die, in plan,
with one sharp rib 19, and four ribs of increasing widths, 20, 21, 22, 23. The
progressive operation of the dies is shown in Figs. 11, 12 and 13.
Fig. 11, a sectional view through the line 5, 5, shows the sharp rib 19, and its
corresponding rib in the fellow die, in position to begin to score the blank,
throughout its length, beginning at the top.
Fig. 12, a sectional view through the line 6, 6, shows the position of all the
working ribs as they act upon the body of the blank, when the operation of
threading is partially completed, the upper threads only being perfect at this
stage.
Fig. 13, a sectional view through the line 7, 7, shows the position of the working
ribs of the dies, acting upon the point of the blank after the body of the blank is
threaded, and has passed beyond the action of the working ribs.
The action of my dies may be compared to the action of a series of chasing
tools upon a blank, cutting threads, in the old fashioned way, each tool cutting a
little deeper than the preceding one, the thread being developed from the root of
the blank towards the point. Of course, the chasing tools cut away the stock,
while my dies act upon it by forcing the metal, by compression, into the V-shaped
spaces between the ribs, in the old and well-known manner in which dies for roll
threading act, although my method of applying the principle is different so far as I
am aware, from any which has preceded it.
In practice, I prefer to use a larger number of sharp scoring ribs, so that the
entire body of the blank may be scored at the beginning of the operation, as shown
in Figs. 1, 2 and 6; besides which, this arrangement of the dies affords a better support
to the blank; but the principle upon which my dies work, is fully illustrated in
Fig. 10, which shows as many working ribs as are necessary for its successful
application, and will roll as perfeet a thread as the die shown in Fig. 1.
If these dies are to be used for rolling a gimlet-pointed thread; they are made to
conform to the shape of the blank, having raised portions along their lower edges,
illustrated in section by Figs. 2, 3, 4 and 5; the ribs of the die extending
sufficiently upon the raised portion to cut a thread upon the point. of the blank.
It will be noticed in Fig. 1, that two or three of the ribs are cut away at the
lower side of the entering end of the die, so that the curved portion of the blank is
not acted upon by the threading ribs until the blank has advanced somewhat in the
process of being threaded.
This is also shown in Fig. 2, wliere, it will be noticed, there are no working ribs

page_text: to act upon the point of the blank, and in Fig. 6, where the point of the blank is
still unthreaded. But, at the line 2-2, Fig. 1, the entire body of the blank
throughout the length of the thread, and also the point, are being acted upon as
shown in Figs. 3 and 7.
If I simply desire to cut a thread on a straight surface, I make the die with a
flat face, as shown in plan, in Fig. 14, and in section, Figs. 15, 16 and 17.
In the drawings, it appears in the sectional figures, that the ribs which are cut
sharp on the top, are cut deeper into the metal than those which are flat on top.
This I find of convenience in making the dies, as it removes any necessity for
changing the cutters; but I can accomplish the same result by using, to form the
sharp ribs, cutters whose working faces are on a greater angle than the faces of
the cutters used in forming the ribs with flat tops, thus cutting the metal at a
uniform depth, for all the teeth.
The operation of my improved dies may be briefly described as follows:
The dies are suitably mounted with their working faces opposite each other, and
their ends reversed, so that, at the beginning of the operation, the sharp ribs in both
dies may act upon the blank at the same time.
A reciprocating motion is then imparted to one or both of the dies, so that their
working faces move by each other; backwards and forwards at the required
speed.
The blank to be threaded is placed in a vertical position against the entering
end of one of the dies.
As the dies pass each other, the blank is rolled along the length of the dies,
first being scored by the sharp ribs, while the series of ribs of increasing width
following, sufficiently compress the metal between them into the grooves of the die
to form the finished thread.
For convenience in illustration, I have shown the ribs and grooves in my die
running diagonally across its face, but it will be apparent that my method of
threading, which develops the thread from the root to the point, by the successive
action of ribs of different width, would permit me to make the ribs and grooves
parallel with the main axis of my die, and therefore, do not limit myself to a die
with ribs running diagonally across its face.
Of course, in operating dies so cut, it will be necessary to arrange the working edges
on an angle with the main axis of the blank, in order to produce a thread of the
required pitch.
Nor, do I limit myself to a die with the ribs and grooves cut on a flat surface,
as a die with a curved surface can be made, on this principle, to work successfully,
or to any particular number of ribs and grooves.
I am aware that dies for rolling threads have been made heretofore, in various
ways, and I do not claim to have invented such, broadly.
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 die for rolling threads upon a blank, having a series of ribs running across
its face, each working rib being wider than the preceding working rib and each rib
being of the same cross-section throughout its working length.
A die for rolling threads upon a blank, having a series of ribs running across
its face, each rib being of the same cross-section throughout its working length;
the first rib of the series having a sharp edge, and each of the remaining ribs being
wider than the preceding one, whereby a screw thread may be rolled upon a blank
by the action of the ribs.
3. A die for rolling threads upon a blank, having a series of ribs running across
its face, each of which is of the same cross-section throughout its working length
one or more of the ribs having a sharp edge, and two or more of the remaining ribs
of the series increasing in width, each being wider than the preceding rib, whereby
screw thread may be rolled upon a blank by the action of the ribs.

page_text: 4. A die for rolling threads upon a blank, having a series of ribs, each of which
is of the same cross-section throughout its working length, the faces of all the ribs
which start from the entering end of the die, being of the same width, and the faces
of the ribs which start from the side of the die increasing in width, each being
wider than the preceding rib, until the required width is attained, when the
remaining ribs are all of the same width, whereby a screw thread may be rolled
upon a blank by the action of the ribs.
Dated this 5th day of December 1893.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London,
Agents for the Applicant.