Improvements in the Straight Dies or Screw-plates of Machines for Cold Rolling the Threads of Screws.
Year: 1892

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by LA SOCIÉTÉ ANONYME LA VISSERIE BELGE, of
Laeken-lez-Bruxelles, in the Kingdom of Belgium.]
Improvements in the Straight Dies or Screw-plates of Machines for
Cold Rolling the Threads of Screws.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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:—
This invention relates to machines for the manufacture of screws, and comprises
improvements in the form of the screw-plates or dies described more particularly in
the Specification of Letters Patent No. 5872 A.D. 1886 for an invention
communicated from abroad by Camille Emile Désiré Winssinger.
These modifications have for their object to improve the form of the blanks
before the commencement of the threading operation to better distribute the
force necessary for the rolling, and thus to obtain more perfect screw threads.
Figures 1, 2, 4, 5, 6, 7 and 8 illustrate the changes of form in question.
Figure 3 is only a reproduction of Figure 2, but to a different scale for showing
more clearly the irregularities in the form of the working face of the die; in
Figure 3 the longitudinal dimensions are one fourth of and the transverse dimensions
three times the corresponding dimensions in Figure 2.
Figure 1 represents a plan of the working face A B C D of a die.
Figure 2 represents an elevation of the same die to the same scale as seen from
the side of the face A D (Figure 1).
Figure 4 represents an elevation of the die as seen from the side of the extreme
face A B. (Figure 1).
Figure 5 is a section on the line A¹ B' (Figure 1) or E¹ H' (Figure 2).
Figure 6 is a section on the line K M (Figure 1) or W L (Figure 2).
Figure 7 is a section on the line Z V (Figure 1) or X U (Figure 2).
Figure 8 is a section on the line N P (Figure 1) or YO (Figure 2).
The scale of Figures 4, 5, 6, 7 and 8 is double that of Figures 1 and 2.
Of course the dimensions of the die may be varied, it being understood that they
depend on the size of the wood screws to be manufactured, or the degree of
hardness of the metal of which they are made and on other facts.
Similar letters designate the various projections of the same points in the several
figures.
The line T T¹ represents the projection of the plane described through the axis
of the blank in case one of the dies is fixed and the other movable.
Before commencing the detailed description of the figures hereinbefore
enumerated.
I may observe 1st, that the two dies are similar in all their portions, but they are
placed in opposite directions; 2nd, that the working face A B C D (Figure 1)
or A AK Z ND (Figure 2) of a die is not parallel with the plane E F
(Figure 2), but is a surface composed of distinct portions diversely inclined to this
plane E F; 3rd, that each of these portions is strictly parallel with the corre
sponding portion of the counterpart die, because the two dies are absolutely similar,
but placed in opposite directions, so that, for example, the face E F (Figure 2) is
placed parallel with the corresponding counterpart face (the counterpart die is, not
represented in the drawing so as not to complicate it); 4th, that this parallelism of
the corresponding counterpart portions is strictly maintained during the relative
movement of the dies, because the said movement takes place in guides which are

page_text: parallel with the plane E F (Figure 2) and with the plare T T¹ developed by the
axis of the blank; 5th, that by reason of these geometric arrangements certain
of the corresponding portions of the counterpart dies approach or recede from one
another during the movement without ceasing to remain parallel with each other.
In order that two portions of the corresponding counterpart surfaces shall
maintain between them the same distance during the movement it is necessary
that they shall not only be parallel with each other but also with the plane T T¹.
After this statement I will proceed to describe the dies. As shown in the
figures, the blank rolls upon the die from A H to D G (Figure 1). The working
face of a die is divided into four distinct regions.
The first region A B B' A' has no grooves and serves to render the cylindrical
parts of the blanks mathematically equal before the impression of the thread. The
exterior surface A B B¹ A¹ (Figure 1) is a plane inclined relatively to E E'
(Figure 2), it may be usefully cut like the surface of a very soft file. The first
section may be dispensed with in case the blanks are of perfect manufacture, that is
to say absolutely round and of the desired diameter.
The second region A' B₁ M K (Figure 1) possesses grooves the profile of which
is shown in Figure 5, [the black lines (Figure 1) represent the thickness of the full
portions of the die, while the white spaces between these lines represent the hollows
in the die]. In the whole Figure 1 the bottom of the bollows lias intentionally not
been represented by a line in order to avoid complicating the drawing which would
lose in clearness.
From the commencement of the ribs A'H' (Figure 1) to the plane KL, the
cross section of the grooves varies but slightly, as shown in Figures 5 and 6, that
is to say the hollows diminish a little in width, and the full portions widen a little.
The exterior surface of all the full portions, remaining intact during the formation
of the hollows, is a plane A¹ K (Figure 2) inclined relatively to E W (Figure 2)
so that during the movement of the blank along this first region, the full portions
enter the metal progressively forming therein a helicoidal groove, the depth of
which approximates that of the groove in the finished screw when the blank has
arrived at K L (Figure 1) and the width of which is still very insufficient.
Figure 6 shows a section of the die and of the blank on the line K L M.
In the third region K M P N (Figure 1) the full parts widen from K. M to NP
much more rapidly than from A B to K M, and the hollows diminish in width,
so that when the blank has arrived at N P, the body of this blank presents its final
shape.
Accordingly the work of this third region of the die consists, principally, in
displacing laterally the zones of metal obtained in the second region and also in
polishing the bottom of the depressions in the blank by pushing them to the final
depth.
Figure 7 represents a cross-section of the die and blank on the line Z V
(Figure 1) the middle of the third region, and Figure 8 represents a cross-section
of the die on the line. N P (Figure 1) with the finished screw at the moment when
it arrives at this point of the die. The dotted line D' Q JR S (Figure 2 and
Figure 3) indicates the projection of the bottoms of the hollows.
The exterior surface of all the full portions of the third region is a plane K N
(Figure 2) slightly inclined relatively to W Y (Figure 2).
In the fourth region N P C D (Figure 1) the exterior surface of the full
portions is still a plane D N (Figure 2) inclined relatively to the plane FY
(Figure 2) for facilitating the egress of the finished screw from between the
dies. The bottoms of the grooves which are in this fourth region, in prolongation
of those which exist in the second, are projected in a straight line D¹ Q parallel
with N D (Figure 2).
The rolling of the thread upon the point of the blank commences only after that
of the thread upon the body of the blank.
From the moment of the arrival of the blank upon the die to the instant when
the impression of the ribs upon the conical point commences, there is no contact

page_text: between the die and the conical extremity of the blank which is to become the
gimlet point of the finished screw.
This important arrangement has the threefold object (a) of allowing full freedom
to the work of perfecting the cylindrical body of the blank which is effected in the
first region. (6) preventing a pressure upon the conical portion (the point of the
blank) from displacing the blank according to its axis in the direction of the head;
(c) enabling the ribs to be forced into the body of the blank.
The pressing of the ribs into the body of the blank must take place before the
formation of the threads upon the point of the blank in order that, during this latter
operation, the blank shall not be displaced between the dies in the direction of the
head.
As soon as the point of the blank commences to receive the impression of
the ribs on the dies it passes through the same stages as the body of the blank.
Whether one of the dies is fixed and the other movable, or whether they are
both movable (in which case the blank turns on the spot), the result as regards the
formation of the screw thread is absolutely the same. It is in fact evident that in
both cases the relative movement of the dies will be identical.
The inoperative portion O P (Figure 8), U V (Figure 7), L M (Figure 6)
H¹ B', (Figure 5), H. B. (Figure 4), is inclined as indicated in the drawings, in
order that the fraginents of metal may not remain imprisoned between the counter-
part dies and produce a resistance to the motion.
My system of rolling screw threads, comprising two principal stages, the first
designed especially for the penetration and the second especially for the widening,
can be applied to the formation of any profile.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed as communicated to me by my
foreign correspondents, I declare that what I claim is :-
In machines for rolling threads of any profile, for instance on wood screws,
the employment of screw plates or dies having working surfaces enabling the
rolling to be effected in three stages, that is to say: a first stage during which
the body of the blank is rendered uniform and smooth before the rolling of the
thread; a second stage during which the ribs enter the blank so as to form
therein a helical groove of gradually increasing depth but of less width than
the final width of the groove in the blank, and a third phase during which the
groove is enlarged, polished and deepened to the final dimensions, by the ribs the
dimensions of which therefore change; and in conjunction with these changes in
the form of the dies, the change of form designed to facilitate the egress of the
finished screw, the change having for its object to commence the rolling of the
screw thread upon the point of the blank only after the rolling of the screw
thread on the body of the blank, and also the change which prevents a portion of
metal to remain between the screw dies, substantially as described and represented.
Dated this 5th day of May 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.