Improvements in Dies for Making Rolled Wood Screws.
Year: 1890

page_text: Date of Application, 11th Nov., 1890-Accepted 13th Dec., 1890
COMPLETE SPECIFICATION.
Improvements in Dies for Making Rolled Wood Screws.
1 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:-
In the Specification to Letters Patent No. 12,730 of September 20th 1887, I have
described and claimed a novel form of die for developing the threads of rolled wood
screws. In that die the ribs are represented as V-shaped, the working faces being
truncated throughout their length, narrow at the commencement or entering end
and gradually diverging therefrom to the opposite end, at which point the grooves
(alternating with the ribs) are the exact counterpart of the thread produced upon the
screw by the dies. In that die the angle or inclination of the sides of the ribs to
each other is constant from one end of the die to the other, although the height of
each rib and the depth of each groove is represented and described as "varying
throughout its length."
The object I have in view in my present improvement is to produce a stronger and
better die, yet one in which the ribs shall retain all the characteristics and advantages
possessed by my patented die before referred to. To that end, my invention consists,
essentially, of a die having at the commencement or entering end ribs and grooves of
the same or a less depth than that of the grooves at the opposite or finishing end of the
die. By reason of such construction the ribs are much less liable to fracture or break
during the process of hardening and tempering the die; moreover, the die when put
into use will last longer, owing to the increased strength of the ribs at the front or
entering end.
In the appended drawing representing my improved die, Figure 1 shows a plan of
the working face of one die; the unshaded parts represent the faces of the ribs.
Fig. 2 is a longitudinal sectional view taken on the oblique linee of Fig. 1;
Fig. 3 is a similar sectional view, showing a modification of the depth of the grooves
and ribs; Fig. 4 is an elevation of the front end of the die; Fig. 5 is a similar
view showing the back end of the die, where the completely threaded screw leaves it;
Fig. 6 is a transverse sectional view taken on line &t of Fig. 1; Fig. 7 is a similar
view taken through a pair of dies placed opposite to each other as in operation,
showing a screw between them in the act of having a thread developed on its surface,
the section corresponding with line o o of Fig. 1; and Fig. 8 is a similar section
taken on line PP.
In the drawings, A designates my improved die as a whole; the parts marked a
indicate the ribs adapted to be impressed into the screw-blank's surface; and the
shaded parts marked b, Fig. 1, indicate the grooves between the ribs. The grooves
are filled in or truncated at the front or entering end and are V-shaped at the opposite
end. The bottom c of the grooves may be parallel with the face of the ribs, as
shown in Fig. 3, or inclined as in Fig. 2, the depth being greatest at the back end of
the die; in fact, the bottom or depth of the grooves need to be considered only with
reference to the gradual development of the screw-threads in a radial direction, or in
other words, the depth of the groove at any point slightly exceeds the height of the
metal raised from the blank, measured from the root of the thread at a corresponding
point; therefore the bottom of the grooves may be inclined, substantially as indicated
by the broken line m, Fig. 2.
The angle of the inclined sides of the ribs a is constant and uniform throughout
the length of the die; but the width of the face or top of the ribs is constantly
varying throughout, or from end to end of the die.
The face of the rib at the end where the rolling commences should be made as

page_text: narrow as is consistent with its strength in order that it may be required to displace
but little metal as it enters the blank. To facilitate its entrance the top may be
slightly chamfered or rounded, as indicated by f. I have found that the ribs, when
the grooves are made to an extreme depth at the entering end as herein before stated,
sometimes break while in action upon the blank, because then the leverage produced
by the lateral pressure of the metal upon the ribs is excessive. Another objection to
an extreme depth of the grooves is that in the process of hardening and tempering
the die, the root of the narrow ribs are much more liable to fracture at such point.
In view of such defects, and in order to overcome them, I have very materially
reduced the height of the ribs at the entering end, as shown.
In lieu of making the faces of the ribs a at a constant inclination throughout the
length of the die, they may be curved, the curvature somewhat approximating that of
a portion of a hyperbolic curve; or the die itself may be made in sections longi-
tudinally, the inclination of the series of ribs of one section varying slightly from its
adjacent section.
The grooves b and the corresponding ribs a may be cut by a revolving milling tool,
the sides of which give the required inclination to the sides of the ribs, the die-blank
being first blocked up at the proper angle, if desired, so that the cutters will cut the
grooves at a varying depth, or as shown in Fig. 2. After the cutting tool has cut
one side of a groove, the tool is set over and again operated so as to form the opposite
side of the groove, the blank at the same time being forced along past the cutter.
After the two sides of the several grooves are cut, the standing stock intermediate of
the adjacent sides of each groove may be cut away or "routed" by a suitable cutting
tool, thus completing the operation.
A manner of forming the threads of a screw by the action of dies of this character
is as follows:
The dies A are oppositely mounted in a suitable machine so as to travel back and
forth past each other (two similar dies A being used, with the ends reversed); a
screw-blank is then placed and held vertically in the space between the opposed ends
of the dies, and as the dies move simultaneously to the right and left, they engage the
blank between them and roll it axially until the opposite ends of the dies pass each
other, when the jaws of the stationary bolder open and the screw drops from them.
At the commencement of the operation the narrow ends of the ribs a of the dies are
forced into the metal to the maximum depth required, or say nearly to the dotted
line m, Fig. 2, at the corresponding end of the dies, and as the rolling progresses the
metal between the ribs is more and more compressed and gradually expands into the
grooves 6 of the dies until, at the end of the operation, it fills them and the thread is
completed.
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
A die for raising the threads of a screw radially from a screw-blank by rolling,
having at the entering end narrow or thin ribs to enter the metal to the required
depth, but increasing in width to the opposite end with the intervening grooves of
the same depth or slightly greater at the entering end than the depth of the groove in
the blank, but increasing in depth to the opposite end to correspond with the
increasing height to which the metal is raised as the rolling progresses.
f October 1890
CHARLES DAKE ROGERS,
Philip M. Justice,
Inventor.
55 & 56, Chancery Lane, London, Applicant's Agent.