Year: 1887

page_text: I, CHARLES DAKE ROGERS, of Providence, in the County of Providence, State
of Rhode Island, United States of America, Mechanic, 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 the threads upon wood-screws by rolling
the blanks between them and raising the metal to form the threads radially from the
body of the blank without extending the blank lengthwise.
The result I seek to obtain is to produce a solid thread, instead of one formed as
shown in a patent of the United States, granted to H. A. Harvey, June 30th, 1885,
and numbered 321,214, where the thread is formed by raising two separate spiral
ridges of metal, which are finally brought together by the action of two dies, which
constantly press the metal towards the axis of the blank, as well as laterally.
considerable part of the pressure of the dies is exerted towards the axis of the blank
to compel the metal to flow away from that axis.
A
With my improved dies, the pressure upon the metal toward the axis of the blank
is limited to the commencement of the rolling operation, and to a comparatively small
part of the metal displaced.
These dies are represented in the annexed drawings, where Fig. 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 line a,, of Fig. 1. The
unshaded portion represents the depth of the grooves, or what is equivalent, the height
of the ribs or bars between the grooves. Fig. 3, is a view of the end of the die where
the rolling operation commences. Fig. 4, is a sectional view on the line 3, s, near the
opposite end of the die. Fig. 5, is a transverse sectional view taken through a pair of
dies placed opposite to each other, and having the screw between them, on line o, o, of
Fig. 1. Fig. 6, is a similar section on line p, p. Fig. 7, is a view of the end of the
die opposite that shown in Fig. 3, and Fig. 8 represents, in perspective, apart from
the rest of the die, one of the thread-forming ribs of the die. The form of the dies
transversely, is indicated by the sectional views 3, 4, 5, 6 and 7. It will be observed
that though the sections 5 and 6 are taken on different lines across the dies, the
diameter of the body of the screw is the same in both Figs. In the several Figs. the
parts marked a, represent the ribs or bars between the grooves, and the parts
marked b, indicate the grooves. See also shaded portion, Fig. 1. These grooves
are V-shaped, the sides having the same inclination to each other as the opposite

page_text: sides of the thread of the screw to be produced. The working parts of a die are
the ribs between the grooves, and the inclination of their adjacent sides to each
other, which. is constant from one end of the die to the other. The work of
raising the thread, is mainly performed by these sides. The angle of the inclined
sides is the same in all, and the same from one end of the dic to the other, but
the height af each rib, and the width of its face or top, varies throughout its
length, and is determined at every point by the depth of the grooves adjacent to
it. One of these ribs, a, is represented in perspective, by Fig. 8, which shows
especially the important feature of the varying width of the top or face. This
top face, which is substantially level, has the form of a truncated wedge, very
narrow at the end, h, where the rolling commences, and much wider at the opposite
end. A dotted line, c, d, on the side, and parallel with the face, indicates the
depth to which the rib may be assumed to enter the body of the blank.
The face of the rib at the end where the rolling commences, should be made as
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, as indicated by the line, Fig. 2.
The grooves in dies of this kind, and the corresponding ribs may be cut by a milling
tool, having a proper form to give the required inclination to the sides of the grooves,
past which the plate to form the die is passed for each groove, the proper form for the
surface of the die having been previously given, and the depth of the cut for each
groove at different points being secured by moving the plate either nearer to, or
farther from the cutter, in conformity to a pattern.
The action of dies of this kind in forming the threads of a screw, may be readily
understood. Let it be assumed that the dic, A, represented by Fig. 1, is a stationary
die, and that a similar die with the ends reversed, is to move back and forth in front
of it, at the proper distance.
To roll a screw the movable die must be carried to the left until its right hand end
is a little past the left hand end of the opposite, or stationary die. A screw blank is
then placed vertically in the space between the opposed ends of the dies, and as the
movable die is carried to the right, the blank is seized and rolled along between them,
until the movable die passes the opposite end of the fixed die, when it drops from
them. At the commencement of the operation, the narrow ribs, h, of the dies are
forced into the metal to the maximum depth required, and as the rolling progresses
the metal between the ribs is more and more compressed and gradually expands into
the grooves of the dies until at the end of the operation, it fills them, and the thread is
completed. In another application of even date, I have described the details of a
machino which operates the dies, and in which the blanks are automatically fed to
them.
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 the thread on screws, having, transversely, the form to be given
to that part of the body of the screw, in the direction of its length, on which the
thread is formed, and having oblique, V-shaped grooves, presenting between them a
series of bars or projections, narrow at the end where they commence to form the
thread, so that they may be forced, at the commencement of their action, into the
metal to the depth required to form the body of the screw, and gradually increasing
in width, act laterally upon the metal between them, and force it into the grooves,
which give it the form required for the thread.
Dated this 20th day of September 1887.
ALLISON BROS.,
Agents for the Applicant.