Improvements in Apparatus for Forging Screws by Rolling.
Year: 1892

page_text: Date of Application, 25th Jan., 1892
Complete Specification Left, 5th Oct., 1892--Accepted, 26th Nov., 1892
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Forging Screws by Rolling.
We, CHARLES FAIRBAIRN of Mayfield, Clarenden Road, Engineer, and
MATTHEW WELLS, Wardle Road, Oil Merchant, both of Sale in the County
of Chester, do hereby declare the nature of this invention to be as follows:-
This invention relates to the construction and arrangement in machines for
forging screws, of the rollers and discs between which the screws are forged.
Such machines as at present constructed are open to various objections which
it is the object of the present invention to remove.
For example, when the screws are forged between the opposed faces of two discs,
the grooves by means of which the threads of the screw are formed are annular
corresponding with the pitch and depth of the threads. The discs are arranged
excentrically with respect to each other and the longitudinal motion of the screw is
produced by the pressure at angles exerted by the discs in rotation. In order to
make the annular grooves of the opposed discs cross each other at a sufficient angle,
their respective axes of rotation have to be separated to such a distance that
the blank or screw shall move through the distance of the pitch for each of its
rotations. Consequently, enough work cannot be put upou the screw to finish it
properly, whilst the thread is partly raised and partly sunk, and the raised half or
portion of the thread has a larger diameter than the blank or unscrewed part. Also,
when the screws are forged between grooves formed on the peripheries of discs
instead of upon the faces tapered screws cannot be rolled advantageously, and owing
to the comparative smallness of the discs they speedily wear out through having to
be rotated at a high speed and to be reversed whilst in motion.
According to my present improvements, when the grooves are formed in the faces
of two opposed discs, instead of making them annular, I form them in spirals over a
comparatively narrow annular band near to the edge of each disc. The grooves
have dimensions corresponding with those of the thread to be produced, and the
distance apart of the grooves is equal to the pitch of the screw. The two discs are
arranged with their working faces parallel or inclined, and opposed, and with their
axes excentric.
The grooves should be equally spaced around the annular band, and the screw
whilst being rolled will make as many revolutions per pitch as there are grooves.
The distance between the axes of the discs will be approximately in inverse
proportion to the number of the grooves; for example for double the number (or
for twice the angle) of grooves, the distance between the centres will have to be
about halved.
If the width of the annular band in which the grooves are formed, is about equal
to or does not much exceed the diameter of the screw, the well known phenomenon
of the production of spongy or hollow centres in the screws does not arise, as is
commonly the case when metal is continuously rolled under pressure between two
surfaces.
The insertion of the blank and the release of the finished screw may be effected
by causing the discs to approach and to recede from each other at the proper
intervals while revolving. This motion may be obtained by means of a treadle, the
screw being supported on an adjustable rest between the discs. Instead of causing
the discs to approach and separate, a portion of the annular band of each disc may
be cut away so as to admit the blank when the removed portions coincide. In this
case the leading ends of the grooves at their commencement in the removed portion
of the annular band, are made shallow and are gradually deepened to the full pitch
or so as to produce any desired degree of taper or to form a gimlet point. In

page_text: some cases the tapering may commence with one groove and two spaces more
being added at equal distances. A plane or roughened feeding rim may be formed
within or outside and concentric with the annular band upon the face of each disc
for forging some varieties of screws.
When the forging grooves are formed upon the peripheries of three discs I divide
each disc into two or more lengths of which the front length is fixed upon its shaft.
The other length or lengths is or are free to move longitudinally upon the shaft,
but so as to rotate therewith but are pressed against the fixed length by means of
an annular or plate spring abutting upon a fixed part of the apparatus. The disc
may be tapered or parallel, but if tapered being largest at the back so as to open
out the shafts and enable larger gearing wheels to be employed. The larger
part of the tapered disc moving at a greater surface speed than the smaller part,
causes the part of the blank in contact with it to revolve at a higher speed than the
surface speed of the smaller part of the disc and consequently a certain amount of
frictional resistance is induced, but the back part of the disc being free to move
longitudinally, the difference in surface pressure is absorbed in the longitudinal
displacement. This arrangement enables tapered screws to be forged with facility
without stripping the threads.
The disc shafts being fixed, some provision has to be made for producing the
necessary longitudinal motion of the screw during the process of its formation.
This is accomplished by giving the discs a twist, and allowance for this twist must
be made in cutting the thread forming groove.
Either right hand or left hand screws may be forged by the discs or both right
and left hand threads may be forged on the same blank simultaneously. In the
latter case, if for example a fish bolt is required with a five-eighths left hand thread
at the point, and a three-quarter right hand thread for the bolt, it is arranged that
the front part of the disc shall form the right hand thread, and the back part the
left hand thread. The larger part of the divided disc will consequently make the
smaller part of the screw and the smaller part of the disc the larger part of the screw.
As the larger amount of work has to be done by the back part of the disc in
reducing the diameter of the blank as well as in forming the screw, the displacement
of the metal results in the elongation of the screw, and but for the transverse
division of the discs hereinbefore described this could not be done.
Dated this 23rd day of January A.D. 1892.
WILLIAM E. HEYS,
Agent for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Apparatus for Forging Screws by Rolling.
We, CHARLES FAIRBAIRN, of Mayfield Clarendon Road, Sale, in the County
of Chester, Engineer, and MATTHEW WELLS, of Wardle Road, Sale, aforesaid,
Oil Merchant, 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 the construction and arrangement in machines for
forging screws, of the rollers and discs between which the screws are forged.
In such machines as at present constructed the screws are forged between the
faces of two opposed discs or between the peripheries of three opposed discs or
rollers. In either case the existing construction and arrangement of the rollers
are open to objections which it is the object of the present invention to remove.
For example, when the screws are forged between the opposed faces of two discs
or rollers, the grooves by means of which the threads of the screw arc formed, are
annular and concentric with the axis of rotation of the disc. The discs are arranged
excentrically with respect to each other and the longitudinal motion of the screw is

page_text: produced by the pressure at angles exerted by the discs in rotation. In order to
make the annular grooves of the opposed discs cross each other at a sufficient angle,
their respective axes of rotation have to be separated to such a distance that the
blank or screw shall move through the distance of the pitch for each of its
rotations. Consequently enough work cannot be put upon the screw to finish it
properly, whilst at the same time, the threads are partly raised and partly sunk,
and the raised half or portion of the thread has a larger diameter than the blank
or unscrewed part. Also, when the screws are forged between grooves formed upon
the peripheries of rollers instead of upon their faces, tapered screws, and screws
having two different diameters cannot be produced advantageously and owing to
the comparatively small diameter of the rollers, they speedily wear out through
having to be rotated at a high speed and to be reversed whilst in motion.
According to our present improvements when the grooves are formed on the
faces of two opposed discs, instead of making them annular, we form them in spirals
over a comparatively narrow band near the edge of each disc. The two discs are
arranged with their working faces parallel or inclined and opposed, and with their
axes excentric. If the forging grooves are formed upon the peripheries of three
discs, we divide each disc into two or more lengths, of which the front length is fast
upon its shaft. The other length is free to move longitudinally upon the shaft and
to rotate freely thereon, and is pressed against the fixed length by means of an
annular or plate spring abutting against a fixed part of the machine.
We will more particularly describe our said invention with reference to the
accompanying drawings, in which,
Figure 1 is a longitudinal section, and Figure 2 a plan of a machine in which
the screws are forged between two opposed discs.
Figure 3 is an end elevation taken to the left of Figures 1 and 2, and Figure 4
is an end view, partly in section, shewing the treadle motion.
Figure 5 is a detail shewing the gearing required to rotate the disc to the
left in an opposite direction to that of the disc to the right.
Figure 6 is a plan of one of the discs shewing the spiral grooves formed on
the annular band on the face of the disc. Both of the discs are formed alike.
Figure 7 is a section through the disc.
Figure 8 is a plan shewing the excentric arrangement of the two opposed
discs.
The discs illustrated
Figure 9 is a section taken along the line æ―y Figure 8.
by Figures 6 to 9, inclusive, are drawn to an enlarged scale.
Figure 10 is a longitudinal section of a machine in which the screws are
rolled between three rollers or discs.
Figure 11 is a sectional end view of Figure 10.
Figure 12 is a back view, and Figure 13 a side view of the discs or rollers,
two only being seen.
Figure 13 is a front view of the rollers. The Figures 12, 13 and 14 are
drawn to an enlarged scale.
Figure 15 is an elevation on a still larger scale of one of the rollers shewing
the screw forming grooves clearly thereon.
Figure 16 is an illustration of a screw having two different diameters such as
might be rolled by means of the arrangement of rollers illustrated.
We desire it to be understood that the construction and arrangement of the
machines apart from the screw forming rollers, forms no part of our present
invention. We have illustrated our improvements as applied to existing machines
in which the rollers are arranged in vertical planes, but there is no reason, other
than that of convenience, why they should not be arranged horizontally and we
may so arrange them without departing from our present invention.
In the machine illustrated by Figures 1 to 4 inclusive, the two opposed rollers
or discs A. A' are rotated in opposite directions from the shaft B, which is driven
by the fast and loose pulleys C. On the hollow spindles D D' are fixed the wheels
E E' which gear, E with the pinion F on the shaft B, and E' with the pinion F¹

page_text: on the stud G, the pinion F' also gearing with the pinion F on shaft B. In
consequence of the intermediate pinion F, the shaft wheel E', and consequently its
shaft also, is driven in the opposite direction to that of E, and the discs rotate
oppositely. The hollow spindle D on which one of the discs is mounted is capable
of longitudinal movement so as to enable it to be brought nearer to or be removed
further from the other disc. This is for the purpose of enabling the heated blanks
to be inserted and withdrawn at the commencement and end of each operation and
is accomplished by the treadle H, which acts through the intermediary of the links
and arms upon the clutch J fixed upon the push spindle K. This acts in one
direction only, the return of the disc being effected by means of the spring L. The
amount of excentricity of the disc is regulated by means of the adjusting
screws M M, and the swing arm G of the gearing shewn in Figure 5, keeps
the pinion fully in gear with the wheel E', notwithstanding the excentricity.
The grooves on the annular band may be set out as illustrated by the diagram
Figure 17. From the centre o, draw as many equidistant radial lines 1. 2. 3.
as there may be desired spirals in the annular band. In the example, there are
supposed to be eight. With any convenient radius, which in the majority of cases
may be taken from 12 to 15 cm., set out the circle a. At a distance equal to about
six or seven tenths of the diameter of the blank to be used in producing the screws,
set out the inner and outer circles b. c. which will form the boundaries of the annular
band. From the point of intersection of circle and radius 2, at an angle of
45 degrees from the radius, set out the line bd, terminating on the circle c.
Bisect . d, and draw therefrom the line ef. From the centre o, draw the line o y,
parallel with b. d, and cutting the line e f. Through the point of intersection i of
the lines ef, and og from the centre o, describe the path of centres p, on which the
centres of all the spiral curves will be found. The radius of curvature of the spirals
is . The line bd, may be at a greater or less angle, according as a flatter or
rounder spiral is desired.
n,
The amount of excentricity between the centres of the disc must be separately
determined in each case, and will vary with the amount of work to be done in
making the screw. The greater the excentricity, the more rapidly will the screw
be forged, but this means also that the whole work of forging must be done in less
For average cases the amount of excentricity may be taken as one half to
three fourths of the radius of the path of centres p.
time.
The edges of the annular band should be bevelled down as shewn in Figure 7.
The insertion of the heated blank, and the release of the finished screw is
effected by causing the disc A. to approach the disc A' after inserting the blank, by
means of the treadle H. As soon as the screw has been forged, the treadle is
released and the spring L then forces the disc back, when the finished screw may
be removed. It is preferred to rotate the discs in such a direction that the blank
is fully inserted, and is forced out by the action of the discs in forming the screw,
in the direction shewn by the arrow Figure 8, where the screw is represented as
being partly formed. The extent of the motion of the disc may be adjusted for
different diameters of screws by means of the usual stop, or by fixing the clutch J
on the push spindle nearer to or further from the contiguous bracket which then
forms the stop.
A plane or roughened feeding rim N may be formed within or outside and
concentric with, the annular band, according to the direction of rotation. Thus, if
the blank moves in the direction shewn by Figure 8, the feeding rim is constructed
inside, if in the opposite direction, outside, the annular band.
The discs may be secured by set screws passing through the flanges 00' formed
upon the ends of the hollow shafts D D¹, and their concentric position thereon
may be secured by forming circular projections thereon which fit within the annular
discs.
When the forging grooves are formed upon the peripheries of three discs, the
machine at present used, which is illustrated by Figure 10, may be employed. In
this machine the screw forming rollers A. A' A' are arranged upon the ends of the

page_text: shafts D D D', on the opposite ends of each of which there is fixed a pinion E
gearing with the internal toothed wheel F by which they are driven. In the front
framing there are radially adjustable bearings M. M. for the spindles of the three
rollers which overhang their bearings. There are also corresponding adjustable
bearings for the spindles in the back framing. The internal toothed wheel is driven
through a pinion on the shaft upon which the driving pulleys C. C₁ are mounted.
These pulleys are driven by a crossed and an open belt respectively so that by
shifting one or other of the belts upon the fast centre pulley, the apparatus may be
driven in ouc direction or the other. The reversal of the motion is effected by the
treadle H which operates the strap fork through the links and levers II. The
lever I is counterweighted, and is capable of engaging with a hook P from which
it may be disengaged by pressing forward the rod Q. On depressing the treadle,
the hook engages with the lever I and the strap fork is thereby held in one
position until it is desired to reverse the direction of rotation of the rollers by
pressing the rod Q, thus liberating the hook and allowing the counter-weight R to
pull over the strap fork so as to bring the other belt upon the centre pulley.
In front of the machine there are two guide bars S, carrying the cross head T,
in which the blanks are held, and in which is also fixed the adjustable stop U,
which, when the blank has been fed forward by the cross head to the required
distance, comes into contact with the end of the rod Q which it presses forward,
thus effecting the reversal of the motion as already described, automatically.
It will be understood that, as in the case of the former machine, the construction
and arrangement are known, and we therefore make no claim thereto, and have
described them only to make the action of the forging discs or rollers more clearly
understood.
We divide each of the discs or rollers into two or more lengths as shewn in
Figure 13, of which the front length is firmly secured to its spindle. The other
length or lengths is or are free to move longitudinally upon the spindle on which
they can rotate, but the motion in the backward direction is resisted by the bow
springs V which abut against the front part of the framing. The rollers may be
parallel, tapered, or have different diameters according to the nature of the screws
desired to be produced, but in each case the larger diameter of the rollers are
towards the back. Tapered rollers are employed for taper screws, and parallel
rollers for parallel screws and their construction is obvious. We have illustrated
and will describe the more difficult case of rollers to produce a screw, Figure 16,
having two different diameters, on one of which there is a right hand, and on the
other a left hand screw thread.
The rollers are respectively set out and constructed so that when they are
mounted upon their spindles, the spherical triangle included between them will just
enclose the blanks, as shewn by Figure 14. Thus, the larger parts of the rollers
will forge the smaller diameter of the screw and the smaller parts of the rollers
the larger diameter of the screws.
The larger diameters of the rollers, move at a greater surface speed than the
smaller diameters, and this differential motion causes that part of the blank which
is in contact with the larger part to revolve at a higher speed, and consequently
a certain amount of frictional resistance is induced, but, the larger part of the
roller being free to move longitudinally, the difference is taken up by this longi-
tudinal displacement. This arrangement enables tapered screws to be forged with
facility without stripping the threads.
Owing to the angular positions of the roller spindles, the rollers have a twist
relatively to the axis of the blank, and allowance for this twist must be made in
cutting the grooves which form the threads as in the existing machines.
As the larger amount of work has to be done by the sliding parts of the rollers
in reducing the diameter of the blank as well as in forming the screw, the displace-
ment of the metal results in the elongation of the screw. But for the transverse
division of the rollers this could not be allowed for.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In screwing machines in which the screws are forged between rotary grooved
rollers, two opposed rollers having spiral screw forming grooves formed on an
annular band on the face of each roller, and having their axes excentric to each
other, constructed and arranged substantially as hereinbefore described and as
illustrated by the accompanying drawings.
2. In screw forging machines in which the screws are forged between opposed
rotary grooved rollers, the combination with spiral grooves formed on an annular
band on the face of each roller, of an annular feeding rim; substantially as herein-
before described and as illustrated by the accompanying drawings.
3. In screwing machines in which the screws are forged between rotary grooved
rollers, and in which the grooves are formed upon the peripheries of the rollers,
dividing each roller transversely into two or more parts of which the front part only
is fixed upon the roller spindle, substantially as and for the purpose herein before
described and as illustrated by the accompanying drawings.
4. In screwing machines in which the screws are forged between rotary grooved
rollers and in which the grooves are formed upon the peripheries of the rollers, the
combination and arrangement with transversely divided rollers the front one of
which alone is fixed upon the spindle, of a spring tending to resist the longitudinal
motion of the back portion or portions of the roller, substantially as hereinbefore
described and as illustrated by the accompanying drawings.
Dated this 3rd day of October A.D. 1892.
WILLIAM E. HEYS,
Agent for the Applicants.