Improvements in Dies for Rolling Drive Screws.
Year: 1889

page_text: Date of Application, 6th Aug., 1889-Accepted, 5th Oct., 1889
טנעUVIII
DI MULTICATION.
Improvements in Dies for Rolling Drive Screws.
I CHARLES DAKE ROGERS of 21 Stevens Street Providence in the State of Rhode
Island United States of America Works Superintendent 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:-
The invention described relates to a die for producing a peculiar wood screw, for
which I have this day made an application for a patent. The die must produce on
the surface of a screw blank, 1st, shallow spiral grooves having transversely a curved
surface; 2d, threads at the edges of the groove raised slightly above the normal
surface of the blank; and 3d, a spiral normal portion of the blank's surface between
two adjacent threads. The die is straight, having its working face provided with
diagonal ribs, grooves and plane surfaces corresponding to the grooves, threads and
normal surface of the blank. The ribs rise, in part, above the plane portions of the
die, and their sides extend slightly below those surfaces, forming the grooves which
produce the thread of the screw. The ribs are convex transversely and in operation
are to be forced into the blank to the extent that they rise above the plane portions
of the surface of the die. The metal which is displaced should flow into and fill the
grooves formed between the ribs and the plane portions of the die. The face of the
ribs which first come in contact with the blank should be a little lower than those
which complete the grooves, in order that the displacement of the metal may be
gradual.
In the annexed drawings, Figure 1 represents one form of my improved wood
screw, a portion of the screw being in section to show the forin of the groove and
threads, one continuous groove being employed. Figs. 2 and 3 are cross sectional
views taken on lines x and ww, respectively. Fig. 4 is a perspective view of my
improved screw having a slightly modified form. A portion of this screw is also
broken away to show the form and arrangement of the grooves and threads which
have a steeper inclination or pitch than the threads shown in Fig. 1, the thread as
drawn in Fig. 4 being what is termed a double thread and having two continuous
grooves. Fig. 5 is a cross-sectional view taken on line o o of Fig. 4. Fig. 6 is a
front view of the die, in reduced scale, showing the working face, the die being more
particularly adapted to produce the threads and groove shown in Fig. 1. Fig. 7 is
an end view of the die. Fig. 8 is an enlarged transverse sectional view taken on
line of Fig. 6. Fig. 9 is a front view of the die, also in reduced scale, having
the ribs and grooves arranged to produce the double grooves and threads shown in
Fig. 4; and Fig. 10 is an end view of the die.
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In Figure 1 is illustrated the conditions required in the die itself, and as shown in
Fig. 6. The shallow spiral continuous groove a, having transversely a curved form,
and the threads c at the edges of the groove raised slightly above the normal surface m
of the blank, have respectively their counterpart in the diagonal raised ribs a',
grooves and plane surface m¹ of the straight die D. In order to produce the
tbreads and groove on the point portion p of the screw (Fig. 1), the face of the die is
raised along its lower edge, as at t³, Fig. 7. The inclination of the ribs and grooves
is such as to produce single-groove screws; the blank being entered at the right of
the die, the ribs a' first acting upon the point of the blank and gradually form the
groove a and the threads c upon the surface of the blank. The dotted lines at the
sectional portion of Figs. 1 and 4 indicate the relative pitch or inclination of the screw
threads. The transverse area of the portion of a rib a¹ extending above the general
face or surface m' of the die is practically equal to the area of the two grooves c
extending below said surface; consequently the metal of the blank which is displaced
by the ribs of the dies should flow into and just fill the grooves c', thereby producing

page_text: a screw having a spiral groove a and screw threads c raised at the edges of the groove
above the normal surface of the blank, and having a spiral, normal surface m between
the threads.
$
In producing the screw shown in Fig. 4; and having a double groove the angle of
the ribs and grooves of the die. form an inclination of about forty-five degrees, as
shown in Fig. 9. The ribs a, are very short at the end of the die (right) where the
rolling commences and gradually increase in length therefrom until the maximum is
reached at the opposite end of the die. A pair of dies.chus made and suitably mounted
would seize a blank at a point mid-way of the portion to be threaded and gradually
form the grooves and threads therein from said point in either direction simultaneously.
The thread produced not extending to the point.
As before stated the face of the ribs at the entering end which first come in contact
with the metal should be a very little lower than the faces of the ribs further along
which complete the grooves in the screw in order that the displacement of the metal
may be gradual. In the use of the die the plane portions m¹ should be brought into
contact with the normal surface m of the blank which is to be preserved in order to
prevent its distortion by the displacement of the metal to form the grooves. It will
be understood that two dies D like that described are to be used in making screws and
that the blank is rolled between them as they move past each other in opposite
directions. They are to be operated in a machine similar to that described in a
U.S. patent granted to me Sept. 20th, 1887, No. 370,353, and also in my U.S. patent
of Sept. 4th, 1888, No. 389,168.
The amount of metal displaced by the action of the ribs a¹ to form the groove a and
thread c is indicated by the dotted line at t, Fig. 3 being a transverse sectional view
of the screw represented in Fig. 1, and Fig. shows a corresponding displacement
of the metal of the screw shown in Fig. 4.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare; that what
I claim is:
A die for rolling screws provided with diagonal ribs and grooves for impressing a
spiral groove into the metal of a screw-blank and raising the metal at the edges of
the groove above the normal surface of the blank to form the threads of a screw,
and with plane surfaces between the ribs corresponding to the normal surface of the
blank to preserve such surface from distortion by the action of the ribs in formning,
the groove and threads.
Dated the 26th day of July 1889.
CHARLES DAKE ROGERS,
Inventor.