Improvement in Self-adjusting Die for Screw Making Machines.
Year: 1887

page_text: Improvement in Self-adjusting Die for Screw Making Machines. {
I, CHARLES DAKE ROGERS of Providence County of Providence State of Rhode
Island U.S.A. 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 present improvement relates to machines for automatically forming the threads
of Wood Screws.
The invention consists in providing one of the thread-forming dies (the other being
relatively stationary) with means whereby in working it is adapted to automatically
accomodate itself (within its limits) to the fellow die.
Heretofore, in machines of the class constructed to form screw-threads upon wood-
screws by rolling the blanks between the grooved faces of reciprocating dies, the
position of the dies with relation to each other has been attained by fixed adjustment.
That is to say, the stationary die and the travelling die are adapted each to be adjusted
both longitudinally and laterally, and then rigidly secured in position in their
respective die-seats or holders. By means of such former arrangement and
adjustinent it is in practice often difficult to turn out screws having perfect threads,
In hardening
owing to the rigidity of the dies and some want of symmetry in them.
the dies they frequently become slightly bent, or warped, thereby throwing the thread
forming ribs somewhat out of truth. In such case they do not act in harmony in
forming the threads upon the blank, while it is being carried along by and between
the rigidly adjusted dies, and thereby imperfect threads are produced.
The object of my invention is to overcome the disadvantages just stated. To
accomplish this result I secure the stationary die in a holder which is both laterally
and longitudinally adjustable. I provide the holder with an elastic support adapted
to vertically maintain the die in its normal relation to the travelling die, yet permitting

page_text: a slight downward movement of the holder against the resistance of the spring.
Should this movement be exceeded a fixed stop serves to prevent further action of the
die in this direction. An adjustable stop is also provided which serves to limit the
upward movement of the holder. The extreme vertical movement of the holder need
not ordinarily exceed one thirty-second of an inch.
This small up and down movement of the holder while rolling the threads, is
produced by the slight inequalities in the dies, as stated, which for the instant possibly
do not exactly "register." By means of this property of the die and holder, it is
enabled to automatically adjust itself to the opposito die. The finished thread is
thereby much more perfectly formed.
The shape of the thread-forming ribs of the dies, adapted to produce a solid screw-
thread raised from the surface of a screw-blank is shown and claimed in an Application
for Patent filed by me, September 20th, 1887.
In the two sheets of drawings herewith :-
Figure 1 represents a plan view, in partial horizontal section, of a portion of a
machine for making wood-screws having a thread-forming die mounted in a holder
embodying my improvement. Fig. 2 is a vertical transverse sectional view, in partial
elevation, taken on the irregular line - of Fig. 1, showing a blank in the act of
being screw-threaded, and also showing means for adjusting and automatically
retaining the normally stationary die in position.
Fig. 3, sheet 2, is a similar sectional view enlarged, showing the end portion of the
holder and the elastic support therofor. Fig. 4, is a detached side view of the
supporting device. Fig. 5 is a reduced plan view of a die holder, adjustably mounted
to move up and down in guides, as distinguished from the pivotally mounted holder
shown in Fig. 1. Fig. 6 is an enlarged sectional view showing symmetrical screw-
threads produced by means of my improvement, and Fig. 7 is a similar view showing
imperfectly formed threads.
A more detailed description of the invention is as follows:-
The machine as a whole, of which only the part having my improvement is
represented herewith, is of the class which produce screw-threads on the screw-blank
by the "rolling process," so called. An example of this type of machine is shown
and claimed in my Application for Patent filed by me, September 20th, 1887.
C, designates a cross-head adapted by suitable means to reciprocate back and forth
in ways formed in the bed or framing B of the machine. The cross-head as drawn is
adapted, by means of oppositely arranged dies a adjustably secured thereto, to roll two
screws during a double-stroke.
These dies are each clamped in a holder b, seated in the cross-head, by nieans of the
bolts and clamping-plate &, as clearly shown in Figs. 1 and 2. The dies being
susceptible of adjustment, longitudinally, by means of end screws 8. The holes in the
holder through which the bolts f, pass being elongated for the purpose. The
clamping-plate b¹ is constructed so as to get a bearing surface upon the cross-head and
the upper side of the die. See Fig. 2.
c, indicates a normally stationary holder-frame whose length is substantially equal
to that of the cross-head. The inner edge of the frame is planed out longitudinally to
receive a die-holder b, which rests upon the lower portion, c², of the holder-frame c.
The manner of mounting and securing the holder and die in position in the die-
holder frame is effected by a clamping plate 6', bolts and screws s, substantially as
just described with reference to the travelling die. In Figs. 1 and 2 the holder-
frame c is represented as pivoted, by screws h, to the thrust-block d. The outer edge
of the frame being semi-circular in cross-section, and fitting a channel c', cut in the
thrust-block, having the counter-part of the adjacent face of the plate. This
construction relieves the pivot screws from lateral thrust and allows it to be
borne by the concave surface c', of the thrust-block. The latter being secured
to the bed of the machine by bolts which are tapped into the bed.
holes therefor formed in the block d being elongated. The thrust-block is backed by
a wedge k, which in turn is backed by a heavy rib or extension projecting upward
from the bed as clearly shown. By means of this latter arrangement the stationary
The

page_text: die is adapted to be nicely adjusted with reference to its fellow or travelling die. A
screw-threaded stem attached to the wedge and passing through a bracket m, in
connection with the check-nuts, serving to facilitate the adjustment. From the
foregoing it is evident that the dio a with its holder-frame c, is adapted to be adjusted
both laterally and longitudinally as desired, and at the same time being adapted to
resist the thrust or pressure imposed upon the dies while rolling the blank between
them.
The immediately following description relates to the more important features of the
present invention:-
Intermediate of the front and rear edges or faces of the die holder frame are stops e¹,
adjustably mounted in ears or extensions e secured to or forming a part of the bed B.
Said stops serving to limit the upward movement of the frame c. Practically, such
movement of the die from its normal position does not exceed one thirty-second of an
inch, as before stated. The distance varying, of course, according to the size of the
screw produced, and the curvature or inequalities of the die itself.
The lower portion or extension e² of the frame c is adapted to be separated from the
underlying adjacent face of the bed frame B, by a like distance. See fig. 3.
In order to maintain the die in its normally stationary position I introduce a series
of automatically yielding supports constructed substantially as follows:
The bed is first drilled from the top near its inner vertical face, thereby forming a
(one or more) hole u. A pintle t, having a slotted opening w² at its lower end, and
the enlargement or head at its upper end, is mounted in said hole, the head
portion, being fitted to move freely therein. A pin w, passing through the
opening w² and secured to the bed serves to retain the pintle in position in the holo u.
A washer w¹, resting upon the pin w, and a strong spiral spring inclosing the pintle
intermediate of the head and washer, serving to normally keep the pin in engagement
with the lower side of the slotted opening w, thereby permitting the upper face of the
pintle to extend only a fixed short distance above the bed. It is obvious, however,
that the extension of the pintle may be readily altered if desired. The resistance of
the spring is such that it considerably exceeds the unsupported weight of the
holder c and its attached parts.
Now, assuming a machine to be provided with the device hereinbefore described, its
operation in rolling a screw would be substantially as follows:-
While
The screw-blank is inserted between the reversely arranged dies a at their entering
end; the movement of the cross-head C in the arrow-direction, Fig. 1, carries the
blank along with it at a rate of speed just one-half that of the travelling die.
the blank is thus being carried forward due to the action of the ribs of the thread-
forming dies the holder e, &c. remains in the normal position represented in Fig. 3,
that is, if the dies exactly agree with each other in their vertical relation at all
portions of the stroke.
Practically, however, such perfection and uniformity of action is not often attained.
Among the causes which produce imperfect screw-threads may be mentioned the
following Slight inequalities in the density of the wire itself; the wear of the cross-
head or other analogous reciprocating parts of the machine, in connection with the
rigidity of the fixed dies. The chief difficulty, however, lies in the fact that the dies
may, and often do, become so curved or warped in hardening that it is impossible to
secure them in such relative positions as to produce perfect threads upon the screw.
The action of the rigidly secured dies being in such case to "thin" the threads, as
represented in Fig. 7, at v¹.
With one of the dies mounted to vibrate or move up and down a short distance from
its normal position, the foregoing defects are overcome, as it automatically adjusts or
accommodates itself to the fixed die in working; the result being to produce screws
having their body threads v, alike in section throughout, as shown in Fig. 6. This
improvement in the mounting of dies I considered very useful, as by its adoption the
per centage of imperfect screws made by the machine is reduced to a minimum.
As before stated, it is not necessary that the holder c be pivotally mounted, it may
be constructed to move vertically between guides g as shown in Fig. 5.

page_text: I prefer to adapt the (normally) stationary die to adjust itself to the the travelling
die, although the latter may be mounted to automatically adjust itself to tho
stationary die.
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 screw-threading machine, the combination with a mounted die for rolling
screw-threads, of a fellow die mounted substantially as described to automatically
adjust itself in a direction parallel to the axis of the screw or blank while being acted
upon.
2. In a screw-threading machine, the combination with a reciprocating thread-
forming die, of a normally stationary fellow die mounted to vibrate parallel to the axis
of the screw or blank while being acted upon, and an elastic or yielding support for
the latter named die, substantially as hereinbefore described.
3. The combination, with a thread-forming die, mounted to reciprocate, of a fellow
die, an adjustably mounted holder having the latter die secured thereto, a yielding
support for said holder, and stops for limiting the movement of the holder and die in
a direction parallel to the axis of the screw or blank, substantially as hereinbefore
described and for the purpose set forth.
Dated this 25th day of Navanhan 1007
CHARLES DAKE ROGERS,
Applicant.