Improvements in Wood Screws and in the Manufacture of same.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Wood Screws and in the Manufacture of same.
I CHARLES DAKE ROGERS of The American Screw Company's Works Providence
in the State of Rhode Island, United States of America Superintendent 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 :-
Wood screws hitherto have been made by a series of operations which may
be specified as follows:-omitting the drawing of the metal into wire and
beginning with the operation which has specific reference to the making of
a screw-
1st. The cutting from wire of a piece required for a screw.
"
2nd. The swaging
of a rough head upon one end of the piece cut off for a screw by
"header or heading
upsetting the metal in a die by means of a machine known as a
machine. The piece of metal is now called a screw-blank.
3rd. The shaving of the entire head thus formed to perfect its form and give it
the required size.
4th. The cutting of a slot across the face of the head.
5th. The re-shaving of the head to remove the burr formed in cutting the slot.
6th. The cutting away of the metal at the opposite end of the piece to reduce it
to a point.
7th. The formation of the thread by cutting a spiral groove around a portion
of the body of the wire or screw-blank so-called. The cutting tool is applied
to the blank several times, making repeated cuttings to complete the thread.
In these operations about forty per cent. of the metal is cut away and becomes
waste.
I have devised a new way of making screws by a different series of operations by
which a large saving of material is effected: a reduction in the cost of making
secured, together with new characteristics and qualities in the screws themselves
which are the result of some of the operations performed, and are made necessary
by those operations.
As in the old process, screws are made by my new process from wire, but for
screws of any specified size the wire is of a smaller diameter; the size having
reference to the diameter of the threaded part of the screw.
But experience has proved that the size of the head should bear within small
limits of variation a certain relation to the diameter of the thread, and the use of
smaller wire for screws of specified sizes than that which has been employed
in the old process involves the upsetting of the metal to form the head to a
greater extent than heretofore, and with an accuracy not before required both as
to form and surface.
In my new way of making screws the shaving of the head and the cutting of the
slot across it, and the re-shaving and the cutting away of the metal to form the thread
are entirely dispensed with and the consequent waste of material is entirely obviated.
The severing from the wire of each piece required for a screw is effected conjointly
with the pointing of the blank by an operation which involves but little waste and
bears as much or more resemblance to forging or swaging as to cutting, and is
entirely different from the common method of pointing a blank by cutting away the
metal as in a turning-lathe. At the same time the end of the wire is brought to a
shape which facilitates the forging of the next head.
In my new way of making screws the following operations are performed:
1st. The head of a screw, including the slot, is formed upon the end of a rod or coil
of wire which is to be made into screws by swaging or forging.

page_text: 2nd. Such portion of the wire on which a head has been formed as is required
a screw is then simultaneously cut-off and pointed to a form and in a manner which
will permit a thread to be forged thereon to the point of the screw.
3rd. The thread is formed by rolling the body of the blank between dies which
force the metal to expand radially into grooves in the die which give the form required
for the thread.
The operation of swaging or forging the head above referred to as a distinct
operation, is in fact a complex operation of several steps or sub-operations similar in
their nature, each differing from the steps that precede or follow it, and requiring a
specific device or instrument to effect its specific object but contributing to the final
result, the production of a screw-head completely formed by forging or swaging.
The screw presents a surface of forged or compressed metal at the parts which are
subjected to the greatest strains, as at the junction of the head with the shank, in the
slot or nick, in the under surface of the head and in the thread. It is well known
that iron or steel articles having such a surface are stronger than articles of the same
size and form and of the same material with a surface formed by cutting. Tests
which have made show that screws made by my new method with a forged or rolled
surface in the parts above mentioned have greater tensile strength and greater strength
to resist the torsional strain of a screw-driver than screws of the same size made of
larger wire and of the same material. The diameter of the threaded portion of the
screw being greater than the diameter of the unthreaded portion and the thread being
thinner, the required hold upon the wood can be secured with less danger of splitting
it than with screws of the common form. The slot in the face of flat-headed screws
being closed at the ends, the liability of the head to split or break is greatly reduced.
The screw-driver is also more readily applied in line with the axis of the screw, and
with less danger of marring the surface of wood into which a screw is inserted. The
surface of the head which rests upon the wood and compresses it, and consequently
the area of the compressed section of the wood itself, is larger than in the wood-screws
heretofore made by the common cutting operations, and thus the wood is better able
to resist the compression of the screw. Other forms of heads can be forged by
suitable dies, such as spherical or conical heads where the slot may be open at the
ends in the usual manner.
The thin raised thread which enters the wood more readily than the common cut
thread, and engages with it more deeply, requires the strength due to the forged
surface and the compression of the metal. The relatively small diameter of the wire
employed to produce a forged thread by radial expansion of the metal, involves the
upsetting of the metal to a greater degree to produce a head of the required
size, and makes it important to secure the strength due to a forged surface
of metal.
The difference in the form of screws made by my new process is found in the
enlarged head and threaded portion of a screw relatively to the shank or unthreaded
portion.
It is obvious that the operations above mentioned must be performed by machinery
which has a definite relation to the results to be socured.
To enable others to practice the method of making screws which I have devised and
to make screws of the kind above mentioned, will now describe the operations in
detail and specify the machinery and devices required to perform them, much of which
I have devised especially for the purpose..
In the annexed four sheets of drawings, Fig. 1, sheet 1, represents a longitudinal
sectional view of a machine, in which the operations of forging a head and pointing
and cutting off a blank are performed. A full description of the operation of the
various parts will be found in my prior specification No. 10039 of 1888.
Figs. 2, 3 and 4, sheet 2, represent, sectionally, proper forms of dies and hammers
for producing flat faced heads having a forged slot closed at the ends. Fig. 5
represents dies in the act of severing the blank from the wire, pointing its end and
moulding the end of the standing wire preparatory to the forging of the hext head.

page_text: Fig. 5 is an end view of one of the dies, enlarged. Figs. 6 and 7 (enlarged) show
the rounded form given to the end of the wire in separating a blank and the form of
the waste material forced out by the closing of the dies. Fig. 8 shows the form
of a screw-blank with a finished head and a conical point. Fig. 9 is a plan of the
face of a head with a forged slot closed at the ends.
Fig. 10, sheet 3, shows a plan of the working face of one of a pair of dies for
forming the threads of screws. The unshaded parts represent the faces of the ribs
which form the grooves in the metal and raise the threads. Fig. 11 is a longitudinal
sectional view thereof, taken on the diagonal line xx, of Fig. 10. The unshaded
portion represents the depth of the grooves or what is equivalent the height of the
ribs or bars between the grooves. Fig. 12 is an enlarged cross section of one of the
dies, taken on line ww. The two dies employed being duplicates. Fig. 13 is a
cross-section of the two dies and of the screw in the operation of forming the thread.
The dies being cut on line m m.
Fig. 14, sheet 4, represents in partial section, a portion of a machine for operating
such dies and forging the threads of screws, and Fig. 15 represents a finished
screw.
which
Referring to Fig. 1, w represents a wire which is to be made into screws. It first passes
through a series of straightening rolls m m of the ordinary construction well known
to mechanics. From these rolls, it passes between reciprocating feeding-clamps a,
which at the proper time grasp the wire and feed forward the length required for a
screw. It next passes between a pair of clamping dies which grasp it at the proper
time and hold it firmly against the action of the heading hammers or dies
forge the head of a screw. When the wire is to be fed forward, it is released from
the hold of the clamping dies. From the clamps the wire passes into and through a
solid die d, so called, in which the head of a screw is to be formed. This die is
formed of a single piece of metal through which there is a hole e of the same diameter
as the wire and through which the wire is forced by the feeding devices. On the
opposite side from that at which the wire enters, the hole is enlarged into an opening e¹
usually conical, corresponding to the form of the screw-head to be produced except
as to its face. The wire is projected through the die sufficiently to furnish the metal
required for the head. In this position it is ready to receive the action of the
hammers which upset the metal, force it to fill the cavity of the die and give it the
form required; the form of the face of the head including the slot being given by the
last hammer which acts upon it. Figs. 2, 3 and 4 illustrate the action of each of
three hammers which act in succession to produce the most common and familiar
screw-head. The first hammer does little more than shorten the portion of wire
protruded through the die and enlarge its diameter, as represented in Fig. 2. The
second hammer compresses the metal still more and expands it against the surface of
the mouth of the die. This hammer also gives a temporary curved form to the face
of the head to prepare it for the action of the third and last hammer. This temporary
curved form is, I find, essential to the proper distribution of the metal with reference
to the forged screw driver slot to be produced in the head by the action of the
succeeding or third hammer.
The action of the second hammer is illustrated in Fig. 3. In Fig. 4 the action
of the final or finishing hammer is illustrated. The face of the hammer rests upon
the face of the die, and the cavity of the die is completely filled with the metal
without overflow. A tongue t on the face of the hammer to form the slot is repre-
sented by dotted lines. The operation of forging the head u of a screw is now
complete. If the face of the hammer and the surface of the cavity of the die is
smooth the head of the screw will be sufficiently smooth for the practical use of
screws. If a finer finish or surface on the face of the head is desired it may be given
by a suitable polishing or shaving-tool without changing the character of the head or
the process by which the screw is formed.
The head being formed, the wire is next fed forward the proper distance for the
length of screw required. The forging of the head expands the metal in the cylindrical
part of the solid heading-die and makes it important that the wire shall be started

page_text: by a feeding device of great power, followed by the action of another device which
carries the wire forward the required length for a screw. The blank c is then
severed from the wire. In connection with the severing perform the operation of
pointing the blank to prepare it for the threading operation. The operation of
severing and pointing is effected by means of a pair of dies s (one of which is
represented by Fig. 5) which are forced against the wire and compress the metal
and bring the end of the blank to a conical point 2, as represented in Fig. 5. At
the same time the end of the wire from which the blank is severed is brought to a
globular or rounded form as represented at e¹ in Figs. 5, 6 and 7. This shape is
of advantage in forging the next head. The dies which effect these results are
shown by Fig. 5 as just stated. I do not regard the severing and pointing of
the blank simultaneously to be an essential part of my process, neither is it in
my judgment essential that these operations should follow the heading operation,
but I think the order I have indicated to be the best way of practicing my
processs.
The only waste of metal which attends my way of making screws occurs
in the severing and pointing of the blanks, and is represented as o o. in Figs. 6
and 7.
The final operation is the forging or swaging of the thread This is effected by
means of two dies, D, between which the blank, c, is rolled. These dies are represented
in Figs. 10, 11, 12, and 13. Fig. 13 exhibits the blank in the operation of rolling,
and shows how the metal is Torced to expand into the grooves, f, of the dies.
Fig. 10 is a plan of the working face of a die. The ligat spaces represent ribs, ",
which enter the metal at their narrow ends (the left being the entering end) to the
depth required to produce the thread, 2. of a screw. Fig. 13 is a transverse sectional
view taken through a pair of dies, showing the screw in the early part of the operation
of forming the thread. I would state that by the employment of my improved dies,
the pressure upon the metal towards the axis of the blank is limited to the commence-
ment of the rolling operation, and to a comparatively small part of the metal displaced.
The working parts of a die, D, are the ribs, r, between the grooves, f, and the
inclination of their adjacent sides to each other, which is constant from one end of
the die to the other. The work of raising the thread is mainly performed by these
sides. The angle of the inclined sides is the same in all and the same from one end
of the die to the other, but the height of each rib, and the width of its face or top,
varies throughout its length, and is determined at every point by the depth of the
grooves adjacent to it. This top face, which is substantially level, has the form of a
truncated wedge, very narrow at the end (at the left) where the rolling commences,
and much wider at the opposite end. This width or face of the ribs, r, at
the finishing end, is the same width as the core of the screw lying between two
adjacent threads.
In order to roll threads upon a blank, c, the latter are placed in a hopper connected
with a machine provided with suitably mounted rolling dies, D. A machine of this
character is indicated by Fig. 14, and is fully described in my prior specification
No. 12729 of 1887. In the present case a portion of the machine being broken away
to show the actuating mechanism, and also showing a blank in the act of being
operated upon by the rolling dies. To roll a screw, the blanks are fod to a holder or
support and held in a vertical position between the opposed ends of the dies, and
(supposing one die to be stationary) as the movable die is carried or forced ahead,
the blank is seized and rolled along between them until the movable die passes the
opposite end of the fixed die, when it drops from them completed, as indicated by
A. in Fig. 15. At the commencement of the operation the narrow ribs of the dies
are forced into the metal to the maximum depth required, and as the rolling progresses,
the metal between the ribs is more and more compressed and gradually expands into
the grooves of the dies, until at the end of the operation it fills them, and the thread
s completed.
It will be seen that in this series of operations all parts of the metal which are
changed in form are subjected to compression to effect that change, and that thereby

page_text: a large reduction in the waste of metal is effected, and that also an important increase in
strength is secured, due to the fact that at the parts, especially where the strain in the use
of the screw is niost severe, a surface of compressed and compacted metal is obtained and
preserved, resulting from the forging operations. This increase in strength, together
with the improved form which results from the raising of the thread radially by.
rolling in the manner described, and the consequent change in the size of the head
with reference to the wire from which it is formed, makes an improved screw,
distinctively and substantially different from the screws heretofore made by the
process of shaving and cutting.
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. The method of forming screws herein described, by forging a finished screw-
head, including the slot upon the end of the wire from which screws are produced,
cutting off from the wire and pointing by compression between dies a piece of the
required size to form a screw, and forging a thread thereon by rolling it between
dies which force the metal by lateral compression to expand radially into grooves in
the die which gives the required form to the thread.
2. A wood screw made with a surface of compressed and compacted metal by
forging or swaging a head in dies including a slot closed at the ends, and by forging
the thread by rolling the screw-blank between dies provided with ribs to enter the
metal and compress it laterally and force it to expand radially into grooves in the
dies which give the thread the required shape and size.
3. As a new article of manufacture, a wood screw having its entire surface
composed of compressed metal as the result of the processes by which the screw
is formed.
4. As a new article of manufacture, a wood screw having the surfaces of the
slot, of the under side of the bead and of the portion of the shank adjacent to
the head of the thread, composed of compressed metal as the result of the processes
by which the screw is formed.
Dated the 20th day of May 1889