An Improved Machine for Rolling Screw-threads.
Year: 1888

page_text: COMPLETE SPECIFICATION.
An Improved Machine for Rolling Screw-threads.
I CHARLES DAKE ROGERS, of Providence, in the County of Providence, and State
of Rhode Island, United States of America, Mechanic, do hereby declare the nature
of my invention for AN IMPROVED MACHINE FOR ROLLING SCREW-THREADS and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:
My improvements herewith relate to the construction of straight dies having
ribbed faces placed opposite each other so as to roll the blank between them in a
machine which imparts a reciprocal motion to one of such dies while the other remains
stationary and acts as a back-rest, or in a modification of such machine which imparts
a reciprocal motion to both dies in opposite directions, one of such dies only being
employed to form the thread while the other acts as a back-rest or guide. Some of
the machines for rolling screw-threads heretofore in use roll the blank between two
cylindrical dies rotating in the same direction, as in the United States patent granted
to Jolun Sheldon, April 7th, 1885, No. 315,349, in which case guiding devices are
required to retain the blank in proper relation to the dies.
Other machines employ pairs of straight dies facing each other, both acting upon
the blank to form the thread, as in my U. S. Patent No. 370,353, of September 20,
1887, in which case any minute disarrangement of the reciprocating mechanisin or
lack of adjustment between the two dies in the pair may produce a distorted thread.
Other machines employ a rotating cylindrical die to form the thread, using a hollow
cylindrical die placed outside and around the acting one as a rest to the blank as in
the United States patent to Clarke and Harvey No. 306,132, October 7th, 1884. In
this form of construction a transverse section of the inner surface of the stationary
die forms a larger circle than the periphery of the acting die and the blank in being
Dins l

page_text: rolled between these two surfaces of unequal length is liable to be twisted and distorted
or the metal is ploughed along by the die in the direction of the spiral groove and
ultimately squeezed out at the point thereby producing imperfect screw-threads.
These defects in previous machines are avoided by the combined use of straight
acting and guiding dies, where the ribs of each die have the peculiar relation to the
ribs of the other which I have adopted.
The accompanying drawings, representing a machine for rolling threads upon wood
screws embodying my improvements, are as follows:-
Figure 1, represents a plan view of a machine having both dies mounted to travel
backwards and forwards. Fig. 2 is a plan view of a machine in which one die travels
backwards and forwards and the other is stationary. Fig. 3 is a transverse sectional
view taken on line of Fig. 2 when the dies are opposite each other. Fig. 4 is a
front view, enlarged, of the acting die. Fig. 5 is a cross-sectional view of both dies,
the acting die being cut at the line.. Fig. 6 is a similar sectional view taken on
line OO, Fig. 7 is a cross sectional view taken on line W W, and Fig. 8 is an enlarged
sectional view showing the relative arrangement of the thread-forming ribs and the
rihs of the back-rest die.
The frame A of the machine may be of any convenient form to support the dies
and mechanism for producing a reciprocating motion of one or both of them.
Such
mechanism is well known and may be varied as desired. In the machine shown in
the drawings the shaft S, by means of the crank band the connecting-rod C, moves
the cross-head m¹ back and forward. The threading die B being firmly bolted to the
cross-head. Fig. 1, represents these reciprocal parts in duplicate, the dies B and B¹
both being movable.
The blank is fed through the inclined ways, m, and, entering the space between
the ends of the dies, as represented in Figs. 1 and 2, is rolled between them, and, by
the pressure of the ribs of the acting die, B, the thread is formed upon the blank
which is held in position by the back-rest B¹.
The peculiarity of the straight dies which I use is shown in Figs. 4, 5, 6, 7 and 8.
The face of the acting die B is provided with a series of inclined parallel ribs o which
have a V-shape at the beginning (Seo Fig. 5) and for portions of their length, and
are then transformed into ridges having the cross section of truncated wedges,
gradually increasing in breadth upon the face to the end. The die B', whether
arranged as in Fig. 1, to move, or, as in Fig. 2, to remain stationary, is provided with
a series of inclined parallel ribs upon its faco similar but reversely inclined to those
upon the face of the acting die B. These ribs for a portion of their length are also
V-shaped in cross section and are then transformed into ridges whose cross sections
are truncated wedges having faces progressively increasing in width to the end of the
die but the sides of the ribs upon this die are less inclined relatively to each other
than the side walls of the corresponding ribs upon the acting die B for the purpose
and with the effect of preventing the sides of the ribs upon the die B from acting
upon the metal of the blank to form the thread which is shaped by the action of the
die B only, thus restricting the function of the die B¹ to acting as a rest only, this
feature of the die is shown exaggerated in Fig. 8.
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 :-
1. In a machine for rolling threads on screw-blanks, a straight die, having formed
upon its acting face a series of inclined parallel ribs which, for portions of their
length, are V-shaped in cross section; and are then transformed into ridges, whose
cross-sections are truncated wedges having faces progressively increasing in width
from the point where they commence to take the truncated form to the end of the
ribs; in combination with a straight back-rest, or die, having upon its face a series of
inclined parallel ribs, similar in form to the series of reversely inclined parallel ribs

page_text: upon the acting die, but of less area in cross section, and thereby adapted to bear
only upon the core of a screw-blank rolled between it and the acting die as described.
2. In a machine for rolling screw-threads on screw blanks, a straight die sub-
stantially as described, in combination with a straight back-rost, having formed upon
its face a series of inclined parallel ribs which are similar to the series of reversely
inclined parallel ribs formed upon the acting die, excepting that the sides of the ribs
which constitute the walls of the recesses between the ribs upon the back-rest are less
inclined relatively to each other than the sides of the corresponding portions of the
ribs of the acting die.
CHARLES DAKE ROGERS.