An Improvement or Improvements in Dies for Forming the Threads of Screws by Rolling.
Year: 1891

page_text: Date of Application, 22nd Jan., 1891
Complete Specification Left, 20th Oct., 1891-Accepted, 21st Nov., 1891
PROVISIONAL SPECIFICATION.
An Improvement or Improvements in Dies for Forming the Threads
of Screws by Rolling.
I JOHN SHELDON, of No. 10 St. Augustine's Road Birmingham in the County
of Warwick, Mechanical Engineer do hereby declare the nature of this invention
to be as follows:-
My invention has reference to dies whether flat or curved employed for impressing
or forming screw threads on screw blanks by rolling; the screw blank being
introduced between a pair of the said dies which are pressed with great force
against the blank while motion is given to the one relatively to the other. The
said dies have ribs upon them which said ribs on the motion of the dies are forced
into the cylindrical surface of the blank thereby communicating a rotary motion to
the blank and displacing metal in the blank outwards i.e. forcing it from the axis
of the blank in a radial direction so that a screw thread is formed of larger
diameter than the diameter of the portion of the blank on which the screw thread
is formed.
The screw thread is formed progressively the ribs of the dies in first operating
on the blank penetrating to the depth or nearly to the depth of the trough between
the threads of the finished screw. There is thus formed a thread with a broad
helical edge. The subsequent action of the ribs of the dies effects the expanding.
of the spaces between the partially formed thread, gradually fashioning the
displaced metal into the finished screw thread.
The perfection of the finished screw thread is dependent on the configuration of
the ribs of the dies, and in order to produce screw threads by the action of pressing
dies equal or nearly equal in finish to the screw threads produced by cutting
give to the ribs on the dies a special form which may be arrived at in the following
manner;-
By means of a circular cutter I cut in the acting face of the die blank, a series
of acute angled depressions or grooves of the size and shape in cross section of the
cross section of the thread of the screw to be made and at a distance apart equal
to the distance apart of the convolutions of the screw threads to be male. These
grooves are inclined to a line which is perpendicular to the normal to the face of
the die and the direction of traverse of the dies at the same angle as the pitch line
of the screw thread will be inclined to the axis of the screw.
.
I now proceed to alter the section of these grooves by cutting away from that
side of each which is the one that is the nearer to the head of the screw and
which I will hereinafter call the upper side. This I do preferably with a revolving
cutter. The piece I take off is of tetrahedral shape and is bounded by two lines
drawn from a point in the upper edge of the groove the one to the entrant end of
the lower side of the next succeeding groove above the one that is being operated
on and the other to the entrant end of the apex of the groove that is being
operated on. The point chosen is preferably about halfway between the entrant
and emergent ends of the upper side of the groove.
The above is the most perfect form of my invention but it is evident that slight
deviations from this exact form may be made without departing from the substance
of the invention which is to vary the section of the grooves in such a manner as
substantially to produce the effect of a groove so shaped as above described.
The die I have described is one of a pair of flat dies constructed according to
my invention both dies of the said pair being alike.
My invention is applicable to curved as well as to flat dies the ribs formed .on
.

page_text: curved dies differing in no essential respect from those made as hereinbefore
described on a flat die.
The machinery by which the dies are worked for the manufacture of screws
constitutes no part of my invention.
Dated the 22nd day of January 1891.
"W. T. WHITEMAN,
Agent for the Applicant.
COMPLETE SPECIFICATION.
An Improvement or Improvements in Dies for Forming the Threads
of Screws by Rolling.
1 JOHN SHELDON, of No. 10 St. Augustine's Road, Birmingham, in the County
of Warwick, Mechanical Engineer, do hereby declare the nature of.my 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 has reference to dies, whether flat or curved, employed for
impressing or forming screw threads on screw blanks by rolling; the screw
blank being introduced between a pair of the said dies which are pressed with
great force against the blank while motion is given to the one relatively to the
other. The said dies have ribs upon them which said ribs on the motion of the
dies are forced into the cylindrical surface of the blank, thereby communicating
a rotary motion to the blank and displacing metal in the blank outwards; that
is, forcing it from the axis of the blank in a radial direction so that a screw
thread is formed of larger diameter than the diameter of the portion of the
blank on which the screw thread is formed.
The screw thread is formed progressively the ribs of the dies in first operating
on the blank penetrating to the depth or nearly to the depth of the trough between
the threads of the finished screw. There is thus formed a thread with a broad
helical edge. The subsequent action of the ribs of the dies effects the expanding
of the spaces between the partially formed thread, gradually fashioning the
displaced metal into the finished screw thread.
The perfection of the finished screw thread is dependent on the configuration of
the ribs of the dies, and in order to produce screw threads by the action of pressing
dies equal or nearly equal in finish to the screw threads produced by cutting I give
to the ribs on the dies a special form which may be arrived at in the following
manner.
By means of a circular cutter I cut in the acting face of the die blauk, a series
of acute angled depressions or grooves of the size and shape in cross section of the
cross section of the thread of the screw to be made, and at a distance apart equal
to the distance apart of the convolutions of the screw threads to be made.
These grooves are inclined to a line which is perpendicular to the normal to the
face of the die and the direction of traverse of the dies at the same angle as the
pitch-line of the screw thread will be inclined to the axis of the screw.
I now proceed to alter the section of these grooves by cutting away from that
side of each which is the one that is the nearer to the head of the screw and which
I will hereinafter call the upper side. This I do preferably with a revolving
cutter. The piece I take off is of tetrahedral shape and is bounded by two lines
drawn from a point in the upper edge of the groove the one to the entrant end of
the lower side of the next succeeding groove above the one that is being operated
on and the other to the entrant end of the apex of the groove that is being
operated on. The point chosen is preferably about halfway between the entrant
and emergent ends of the upper side of the groove.
The above is the most perfect form of my invention but it is evident that slight
deviations from this exact form may be made without departing from the substance

page_text: of the invention which is to vary the section of the grooves in such a manner as
substantially to produce the effect of a groove so shaped as above described.
The die I have described is one of a pair of flat dies constructed according to
my invention both dies of the said pair being alike.
My invention is applicable to curved as well as to flat dies the ribs formed on
curved dies differing in no essential respect from those made as hereinbefore
described on a flat die. Their shape will be substantially the same as though
they had been made as above described and subsequently bent to the required
curve.
The machinery by which the dies are worked for the manufacture of screws
constitutes no part of my invention.
I will now proceed to describe with reference to the accompanying drawings the
manner in which my invention is to be performed.
Figure 1 represents in plan, a die blank after it has been operated upon by the
first cutter in the manner hereinafter described. The said die blank before being
operated upon by the said first cutter is an oblong block or slab of soft steel having
in end elevation the configuration which will be understood by reference to
Figures 5, 6 and 7 that is, the outline of the said figures or the configuration
of the said figures without the angular depressions & there represented. It will be
seen by the said Figures 5, 6 and 7 that about one third of the face of the said die
is inclined at a very obtuse angle to the other two thirds the said inclined part of
the face of the die operating on the taper end of the screw blank the other part of
the said die operating on the cylindrical part of the screw blank.
Figure 2 represents the die blank Figure 1 after it has been operated upon by
the second cutter.
Figures 3 and 4 represent in plan and side clevation respectively one of the
finished dies Figures 5 and 6 represent end elevations of the front and back ends
of the said finished dic, and Figure 7 represents a section taken on the line a c
Figure 3.
Figure 8 represents in front elevation the first cutter and Figure 9 represents
the said first cutter in edge view in the act of cutting one of the depressions or
grooves.
Figure 10 represents in front elevation the second cutter and Figure 11 represents
the said second cutter operating on the die blank in which grooves or depressions
have been cut by the first cutter. The said Figures 8, 9, 10 and 11 are drawn to
a smaller scale than the other figures of the drawings.
In the several figures of the drawings the finished die and the die blank in the
various stages of its manufacture is marked a and corresponding parts of the said
figures are marked with the same letters of reference.
In making one of the dies constituting my invention I take a blank of the kind
herein before described and I operate on the upper or acting face of the die blank
by means of the circular rotating cutter Figures 8 and 9.
By the operation of the said first rotating cutter I cut a series of parallel acute
angled depressions or grooves b, b in the face of the blank the cross section of the
said grooves being similar to the cross section of the thread of the screw to be
made and at a distance apart equal to the distance apart of the convolutions of the
screw thread to be made. It will be seen by reference to Figure 1 that the
grooves b, b made in the acting face of the blank a are not perpendicular to
the ends or shorter sides of the said blank a the said grooves b making with the
ends or shorter sides of the said blank a the same angle which the thread of the
screw to be made makes with the axis of the screw.
When the rotary cutter reaches the inclined part of the blank a the said cutter is
gradually raised not only for the purpose of following the incline on the face of the
said blank a but for producing shallower grooves in the said inclined part than in
the other part of the blank.
After the grooves b represented in Figure 1 have been made by the first cutter
I proceed to alter the section of the said grooves by cutting away from that side of

page_text: cach groove
which is the one that is the nearer to the head of the screw. This
I effect by the use of the rotating cutter represented in Figures 10 and 11. In
Figure 11 three of the grooves on the left hand side of the said figure are
represented as having been operated upon by the cutter, the acting part of the said
cutter being represented in the third groove. The other grooves in the said figure,
that is, the grooves on the right hand side of the cutter are represented of the form
made by the first cutter, that is, the said grooves have not been operated upon by
the said second cutter.
When operating with the second cutter, the said cutter is in its lowest position
when commencing to operate on the grooves but gradually rises as the blank
advances under it and rises still more rapidly when the inclined part of the said
blank comes under its operation. By this rising motion of the cutter less and less
portions of the side of the groove operated upon are cut away as the blank
advances under the said cutter.
The die in this stage of its manufacture is represented in plan in Figure 2 and
need not be further operated upon but I prefer to cut away a portion of the
inclined side as represented in plan and side elevation respectively in Figures 3 and 4
as it is undesirable to operate on the tapering end of the screw blank until the
thread on the cylindrical part of the screw blank has been partially formed.
By reference to Figures 1, 2, 3, 5, and 11 the change which has been made by
the operation of the second cutter in the grooves made by the first cutter will be
understood. For the purpose of facilitating the comparison of the several figures
I have indicated the summits of the ribs by the letter e the grooves or depressions
between the said ribs being indicated by the letter b. The upper boundary of the
parts of the ribs c in Figure 1 which are cut away by the second cutter so as to
produce the grooves represented in the die blank Figure 2 is shown by the dotted
lines in Figure 1.
C
The parts of the grooves of the blank not operated upon by the second cutter,
that is, the parts on the right hand side of the line y, y Figure 2 have for their
function only the smoothing or finishing of the thread formed by the other parts of
the die.
The die made in the manner herein before described is hardened and tempered
in the usual way.
Although I have described the formation of the grooves or depressions in the die
by the use of rotating cutters yet I do not limit myself thereto as the said grooves
or depressions may be made by planing or otherwise, the essence of my invention
consisting not in the manner of making the grooves or depressions but in the kind
of grooves or depressions however made. In order further to illustrate my
invention I have represented in outline only (that is without shading) in Figure 12,
the surface and end elevations of a die having three ribs of the ordinary kind the
forming parts only of which are represented. The lines u, u indicate the positions
of the middle of the troughs between the convolutions of the screw thread formed
by the ribs and it will be seen that the ribs are symmetrical with respect to the
said lines, that is the two sides of the ribs are alike. In Figure 13 I have
represented in outline only (that is without shading) the surface and end elevations
of a die having three ribs made according to my invention the forming parts only of
which ribs are represented. The lines, indicate the positions of the middle
of the troughs between the convolutions of the screw thread formed by the ribs,
It will be seen that the ribs in Figure 13, that is, the ribs made according to my
invention are not symmetrical with respect to the said middle lines of the troughs.
The screw thread formed by ribs of the kind represented in Figure 12 is formed
of metal gathered equally from both sides of the grooves or depressions; while
the screw thread formed by ribs of the kind represented in Figure 13 is formed of
metal gathered almost wholly from one side of the grooves.
Screws made by dies having ribs of the kind represented in Figure 12 are
defective in the respects that that portion of the screw thread nearest the head of
the screw is not well developed that is, is not brought up to a sharp edge while the

page_text: thread on the tapering point is still less developed, while screw threads made by
dies having ribs of the kind represented in Figure 13 are well developed in every
part, that is, from the setting in of the thread near the head to its termination on
the taper point of the screw.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that I claim as
my invention of "An improvement or improvements in dies for forming the
threads of screws by rolling
Making the said dies with inclined parallel unsymmetrical ribs shaped substan-
tially in the manner hereinbefore described and illustrated in the accompanying
drawings whereby the blank operated upon by the said dies has first formed in it a
groove or depression of (or of about) the depth of the trough between the con-
volutions of the thread of the finished screw which groove or depression by the
progressive action of the die is gradually widened mainly on one side and the
displaced metal gathered up, mainly on one side, formed into the finished screw
thread.
Dated the Twentieth day of October 1891.
W. T. WHITEMAN,
Agent for the Applicant.