An Improvement in Wood Screws.
Year: 1890

page_text: Date of Application, 17th June, 1890-Accepted, 19th July, 1890
CUMI LEIN DICITIATION
An Improvement in Wood Screws.
1 CHARLES DAKE ROGERS of 21 Stevens Street Providence in the State
of Rhode Island United States of America, Works 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:
In rolled wood-screws having enlarged screw-threads, that is screws in which the
diameter taken across the threads exceeds that of the normal size of the wire or
unthreaded portion, it is usual with some manufacturers to make the head of the screw
enlarged, as compared with the shanks of ordinary wood screws, the size being deter-
mined by or having a certain ratio to the diameter of the threads, instead of the wire
itself. In the ordinary standard wood screw having cut threads the diameter is
substantially uniform throughout except at the point portion, the diameter of the head
exceeding that of the wire by a certain number of sizes or gauges. It was
undoubtedly this fact which caused certain rolled-screw makers to adopt the pro-
portions used by manufacturers of cut screws, the difference being that in the former
case the diameter of the thread is taken as the unit of measurement instead of the
In view of these facts it is evident
wire itself, as in the latter case as before stated.
that the amount of metal composing the head of a rolled screw having enlarged
threads is much greater than in the head of an ordinary or cut wood screw, at the
same time the lateral projection of the side of the head, at its junction with
the shank obviously considerably exceeds that of the head of a cut screw, there-
fore the head of the rolled screw is not quite so stiff in a lateral direction nor is
it capable of resisting so great a torsional strain as a screw having a shank of larger
diameter.
Attempts have been made to overcome the defects just referred to by increasing the
amount of metal at the intersection of the shank with the head. In the specification to
a Patent granted to me July 22 1887, No. 10,250 (in Great Britain), I have shown
and described a rolled wood screw in which the neck portion or unthreaded part of the
screw has a substantially cone-shaped form. While such construction enables the screw
to withstand greater strains which may be applied to it in lateral and torsional
directions, yet substantially the same result may be attained by a less quantity of
metal distributed in a different manner.
The object I seek to attain is to stiffen and strengthen the beads and unthreaded
shanks of rolled wood screws provided with enlarged threads, at the same time disposing
the metal for the purpose so that only a minimum amount of stock is required. To that
end my improvement consists in providing the cylindrical shank with a series of com-
paratively narrow integral projecting ribs which commence at or near the beginning of
the thread and extend longitudinally therefrom in a divergent direction until they
intersect the side of the head at a point which measured across the head is substantially
equal to the diameter of the screw taken across the enlarged screw-threaded portion.
The stock which I preferably use for screws of this class is that known as "low steel" or
homogeneous metal, because in order to produce heads upon the screw-blanks the
metal is necessarily upset or swaged to a much greater extent than would be required
for the heads of common cut screws. The ribs are formed upon the blank simul-
taneously with the forming of the head, by upsetting the metal in a heading die
provi led with a corresponding number of grooves having the form or counterpart of
the ribs to be produced.
In the accompanying drawing; Figure 1 is a side elevation of an enlarged rolled
threal wood screw provided with my improvement; Fig. 2 is a similar view of a
drive-screw or screw-nail having enlarge multiple threads or spirals of coarse pitch,
and also provided with a series of strengthening ris; Figs. 3 and 4 are cross-sectional

page_text: views taken on lines ar and m m respectively, of Figs. 1 and 2, and Fig. 5 is a side
elevation of the headed screw-blank before being subjected to the screw-threading
machine.
Referring again to the drawings, n indicates the body or shank of the screw-blank
and also the unthreaded portion of the completed screw a, contiguous to the head h.
In Fig. 1 the screw-threads are raised from the body of the blank by the rolling
process, that is the blank is placed between a pair of reciprocating dies provided with
suitably shaped ribs and grooves which act to raise the thread, the metal flowing
Interally instead of longitudinally, the diameter across the thread considerably exceeding
that of the blank or unthreaded portion n. The screw-nail shown in Fig. 2 is produced
in a similar manner to that just described, the form of the thread-forming ribs and
grooves of the dies obviously being modified. In the screw-nail the space or root t'
of the threads is curved, whereas that of the screw shown in Fig. 1 is straight or
cylindrical as at n'. As hereinbefore stated the head is equal to that of a common
screw whose shank has a diameter the same as the screw thread t, consequently the
heads of such rolled screws contain more metal. It will be seen that the screw
presents an apparent structural weakness at the point where the shank n and the head h
unite, or on the line ca; in order, therefore, to increase the strength and stiffness of
such rolled screws at the point named, I provide the shank with a number of raised
ribs c which commence say at the beginning of the screw-thread t and extend there-
from in a divergent direction longitudinally of the shank, and finally terminate in the
side of the screw-head at a point which if prolonged therefrom would touch and he
parallel with the outer edge of the screw thread, as indicated by the dotted line o, and
also parallel with the axis of the screw. These ribs or feathers c are produced in the
heading dies which bave corresponding-shaped grooves cut therein for the purpose;
the metal of the wire or rod from which the blank is made being upset into them
simultaneously with the forming of the head. Obviously the number of the ribs and
the shape of them transversely may be varied from those represented by the drawing
without departing from the spirit of the invention.
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
A screw having its shank or unthreaded portion provided with longitudinal ribs or
projections extending from the head towards the threaded portion.
Dated the 15th day of May 1890.
CHARLES DAKE ROGERS,
Inventor.