Improvements in Screw Nails and in the Method of and Means for Producing same.
Year: 1890

page_text: Date of Application, 18th Feb., 1890-Accepted, 22nd Mar., 1890
COMPLETE SPECIFICATION.
Improvements in Screw Nails and in the Method of and Means for
Producing same.
I CHARLES DAKE ROGERS of Providence (21 Stevens Street) in the county of
Providence and State of Rhode Island United States of America Works Superin-
tendent 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 :-
The object I have had in view in the improvement I am about to describe is to
produce a nail from drawn wire which shall have a greater holding capacity with less
liability to cripple in driving than the ordinary wire nail as heretofore made. The
tenacity of wire is so great that a wire nail of a given cross-section will resist a much
greater tensile strain than the common cut nail of the same cross-section and will be
much less liable to break from bending. But as its surface is smooth it is necessary
to drive it into the wood to a considerable depth to ensure sufficient adhesion to the
wood to give it an efficient hold. On the other hand, if the nail is made long to give
it the necessary holding capacity it is somewhat liable to be bent or crippled in
driving, and this liability makes a larger diameter necessary than the tensile strain
simply would require. Attempts have been made heretofore to make driving screws,
or screw nails, that is, screws with threads of a steep pitch which could be driven
into wood with a hammer turning on their axes as they penetrate the wood.
In one instance the screw was provided with five parallel threads or grooves having
a pitch of about forty-five degrees with the axis of the screw; the screw apparently
was to be made by cutting grooves into a wire after the manner of common wood
screws, for the diameter measured across the ribs is the same as the wire. This would
entail a considerable waste of material and make the cross-section of the metal in the
grooved portion considerably less than the cross-section of the wire and render it
more liable to cripple under the blows of a hammer, and as the spirals of themselves
increased the resistance to the entrance of the nail into wood, the liability to cripple
under the hammer would be much increased. These inherent defects in the article
and the cost of making it would be quite sufficient to explain its failure to go into
permanent practical use.
It is a very common practice for workmen to drive the ordinary wood screw into
wood for the whole or a part of its length with a hammer, and in the latter case to
finish the insertion with a scrow-driver. A common wood screw when thus driven
into wood by a hammer like a nail, breaks up the fibers of the wood to such a degree
that it has but little hold upon the screw, excepting from the point where the screw
driver was used. Figs. 1 and 1 of the annexed drawings made from a photograph
of the two converse pieces of wood into which a screw had been inserted in the
manner above stated, show the effect upon the wood of driving a screw into wood
with a hammer, as a nail is driven. Fig. 2 is a like illustration of the effect upon
the wood of the insertion by driving with a hammer, of a screw which has heretofore
been made and used to a considerable extent, and which is provided with a peculiar
thread which is intended to facilitate the advance of the thread into the wood. It is
designed to be withdrawn like ordinary screws by turning, the thread baving the
ordinary pitch.
To secure a good hold of a screw or nail into wood it is important that the fibers of
the wood should be as little broken up as possible by the entrance of the screw or nail.
In driving a screw of the ordinary pitch into wood with a hammer the fibers of the
wood are so broken up by the threads that the holding capacity of the thread is greatly
sacrificed, and even when threads of a steep pitch are cut in a wire, the waste material
and diminution of strength counterbalance to a great extent the holding capacity due
to the spiral threads.

page_text: It should be borne in mind that a nail or screw forces its way directly into the
wood, and that upon the shape and condition of the walls of the cavity which it
forms, the holding power depends more, ordinarily, than upon the tensile strength of
the metal which is generally more than sufficient to resist the direct strains brought
upon it.
A screw in fact forming the nut with which it engages. I give to my
nail the ability to form a cavity which as to the strain upon it and its withdrawal
acts like the nut to a screw. The walls of this cavity are made up of the com-
pressed fibers of the wood instead of the disintegrated fibers which are the result
of driving a common screw into wood like a nail. The effect which the insertion
of a nail or screw has upon the fibers of the wood has not I believe heretofore
received the consideration which it deserves. In the manufacture of nuts and bolts
this matter has not been overlooked and cold-pressed nuts are made to secure a holding
capacity equal to that of the bolt.
I have, by adopting a new way of making screw-nails from wire, produced an
article differing from any nail or screw so far as I am aware heretofore made, in
its form, and in the condition of the metal, which can be readily forced into wood
by the blows of a hammer without breaking up the fibers of the wood and can
be withdrawn by turning like an ordinary screw. Figs. 3 and 4 represent in
elevation two of my nails, one of them provided with a head h similar to the
common head of a screw. Figs. 5 and 6 represent longitudinal sections taken
through the centre of these nails respectively. Fig. 7 is a transverse section, taken
through the fluted portion of said nails on line a a. Fig. 8 is a transverse sectional
view taken on line o o, through the wire or unfluted portion of the nail shown in
Fig. 3.
The cylindrical surfaces of my screw nails are in whole or in part fluted
spirally by the compression and displacement of the metal by two dies between
which the wire is rolled. It will be observed where the fluting does not extend
over the whole surface that the diameter at the edges of the spirals is greater than
that of the wire where the surface is plain. In the enlarged cross-section shown in
Fig. 9, the interior circle represents the diameter of the screw nail at the bottom of
the flutings a. The outer circle represents the diameter of a circle just touching the
edges of the flutings. The intermediate circle represents the original diameter of the
wire. The space occupied by the metal outside of this circle is very nearly the same,
but slightly less, than the space of the flutings inside the circle. The cross-section
of the metal in the finished screw nail is therefore only a trifle less than the cross-
section of the original wire, the difference being due to a slight elongation of the
wire in the rolling to which it is subjected. By reason of the condensation of the
metal in rolling to produce the flutings, and of the increase in diameter as indicated
by the outer circle, the fluted nail is stiffer and therefore less liable to be crippled in
driving than the original wire, and very much less than when the metal of a wire of
the same size is cut away to produce spiral holding surfaces. This nail can be cheaply
made without waste of material and can be driven into wood without crippling and
without breaking up the fibers of the wood, but on the contrary compressing the
wood and thus giving it a greater holding capacity. The flutings of the whole
cylindrical surface of the nail as represented in Fig. 4, permits the head to be dis-
pensed with, and yet secures efficient holding capacity. Fig. 10 made from a photo-
graph of the two converse sections of wood into which my nail had been driven,
shows how the integrity of the wood is preserved under the insertion of the nail.
Also by reason of the greater stiffness of my nail due to the enlargement of its
diameter as above explained, and to the condensation of the metal in rolling and to
the increase of holding capacity due to the increase of holding surface and its
obliquity to the axis of the nail and to the compression of the wood, a smaller and
shorter nail than that commonly used will perform the same duty. In trials which I
have made I have found that a fluted nail of a given length had a greater capacity to
resist tensile strain without being withdrawn from the wood into which it had been
driven than smooth nails of the same diameter and twice the length. I am satisfied
from my trials that my screw nails having a greater holding capacity than the smooth
wire nails now in use, will require less than half the material. Fig. 11 represents

page_text: an ordinary smooth wire nail. Fig. 11* represents a fluted nail having a corre-
sponding or greater strength and holding capacity. In this latter nail the length is
but one-half that of the smooth nail, and its area in cross-section is less, consequently
less than half the material is required as just stated. My fluted nails can be more
readily driven, and if provided with heads, as easily withdrawn.
I believe the circular form e in cross-section of the Hutings to be better adapted to
preserve the integrity of the wood than any other form. The number, pitch and
depth of the flutings may be varied, but must be sufficient to ensure the turning of
the nail as it is driven.
The dies d by which I produce my nail are represented in plan or face view by
Fig. 12, and in section through the middle longitudinally on line m m, by Fig. 13.
The working face of this die is provided with diagonal ribs r making with the middle
line of the die an angle of about forty-five degrees. The surfaces of these ribs are
rounded to correspond with the flutings a of the nails produced. A portion of these
ribs are planed down to a little more than one-half of the depth of the grooves between
them, as shown at e, thus giving such portions a flat surface which bears upon the
normal surface of the wire as it is rolled between the dies, but which does not displace
the metal. By reason of this construction which makes the ribs short which first
engage with the metal the flutings are commenced at the middle of the part of the
blank to be acted upon and advance progressively in opposite directions. The dis-
placement of the metal to form the flutings is effected by the unplaned part of the
ribs which extend above the plane of the planed surfaces, and the grooves g between
the ribs below such surfaces receive the metal which is displaced, with the exception
of a small amount which goes to the elongation of the wire. Figs. 14 and 15
represent the front and back ends of the die respectively. Fig. 16 is an enlarged
partial cross-sectional view, taken on line ww, of Fig. 12 at the forward portion of
the die. Fig. 17 is a similar view, taken at at the opposite end of the die, and
Fig. 18 represents a vertical transverse sectional view taken through a pair of dies
and also showing a fluted nail between them. Two of these dies are placed in a
machine which gives them reciprocating movements in opposite directions and in the
direction of their lengths. They are to be placed at such a distance apart that the
planed surfaces e of the ribs will just bear upon the surface of the wire to be operated
upon. A machine suitable for operating such dies is described in my British Patent
Specification No. 12,729, dated September 20, 1887, but machines of different
construction may well be employed.
The wire or blank for a nail is to be so placed between the dies that the rolling and
the consequent formation of the flutings will be commenced at the middle of the
portion to receive the flutings which will proceed sinultaneously and progressively in
opposite directions to the ends, the wire being left free to expand slightly each way.
The form of the nail and the condensation of the metal are due to the action of these
dies in rolling the wire, and so far as I am aware these features cannot be secured by
any other means now known.
.
The action of these dies d in fluting the metal differs in a marked manner from the
action of the dies employed to produce the thread of the screw described in United
States patent granted to H. A. Harvey, numbered 321,214, and from a die previously
invented by myself for producing a rolled screw with a raised solid thread, and
described in British Patent Specification dated September 20, 1887, and numbered
12,730.
In these last named dies the ribs and grooves are but slightly inclined to the line
of motion of the dies. The Harvey die acts mainly by pressure towards the axis of
the screw-blank, and each rib of the die spreads the metal laterally on both sides with
the result that seamed and therefore defective threads are produced. The dies act in
rotating the blank like frictional gears.
In my dies, described in my Specification above referred to, I provided ribs which
after they had entered the metal acted like wedges to press the metal sideways on
both sides but in such a manner as to raise a solid thread. These dies also act in
rotating the blank like frictional gears. In my present dies, by virtue of their large

page_text: inclination to the line of motion of the die, the ribs r engage with the metal as a
rack engages with a pinion; the pressure of the ribs upon the metal being not only
in the direction of the axis but also in the direction of the line of motion, so as that
the flow of the particles of the metal is, I believe, mainly in the same direction. The
result is the production of a solid compressed nail having a tensile strength and
stiffness due not merely to the normal condition of the metal but to its compression
and radial enlargement, as above explained.
The production of my improved screw nails involves a new way of operating on the
wire blanks and new and peculiar dies to effect that operation.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is-
1. The method herein described for impressing spiral flutings into the surface of
wire blanks of a pitch and depth which will permit the finished screw-nail to be driven
info wood and turn on its axis as it advances.
2. The spiral fluting dies herein described provided with diagonal ribs which engage
with the metal of a blank between them and form by its compression the flutings
progressively in opposite directions from the points of engagement.
3. A rolled screw nail having the flutings of such depth and pitch that when the
nail is driven into wood by the blows of a hammer it will be compelled as it advances
to turn on its axis.
4. A rolled spirally fluted wire nail or screw-nail with the edges of the flutings
raised above the normal surface of the wire, and having the flutings of such depth and
pitch that when the nail is driven into wood by a hammer it will turn on its axis as it
advances.
Dated the First day of February 1890.
CHARLES DAKE ROGERS,
Inventor.