An Improvement in Wood Screws.
Year: 1889

page_text: Date of Application, 4th June, 1889-Accepted, 20th July, 1889
COMPLETE SPECIFICATION.
An Improvement in Wood Screws.
I CHARLES DAKE ROGERS of the American Screw Company's Works 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:-
My invention relates to an improvement in wood screws, having the thread raised
from the body of the blank by compression, and by rolling, between dies provided
with oblique grooves into which the metal is forced by the ribs between the grooves.
Screws of this character are described in a patent of the United States, granted to
H. A. Harvey, June 30, 1885, and numbered 321,214. The spiral groove between
the threads described in that patent is formed by dies which are gradually forced
axially into the metal, from the commencement of the operation to the end, so that
the groove is gradually deepened and widened and the metal is forced outward from
under the ribs of the dies, thereby forming two ridges, which gradually spread apart
and increase in size, as the rolling progresses, until the two ridges between two
adjacent parts of the groove of the screw are brought together and to an edge in
the groove of the forming die. The thread thus formed is not a solid mass of metal,
but has a seam running through it, where the two ridges are brought together.
The improved screw which I produce has a solid thread, which is the result of a
different mode of operation in raising the thread. This solid thread possesses the
following advantages over the seamed thread described in the patent referred to: It
is stronger, and can be raised higher so as to take a firmer hold of the wood into
which the screw is inserted.
The thread can also he made thinner, and therefore be more easily inserted in the
wood. Practically a larger screw can be made from the same blank than can be
made when the thread is raised in the way described in the patent referred to.
Figure 1, of the drawings hereto annexed, shows a section, enlarged, of a portion
of a screw, having the thread described in the patent referred to, exhibiting the
seam running through the thread.
Fig. 2 shows a similar section of my improved screw. The succeeding Figs., from
3 to 9, inclusive, show elevations of a blank from which a screw is formed, and of the
the
partly formed screw at several stages of the operation of raising the thread;
last, Fig. 9, representing a finished screw. Below these last Figs. are enlarged
sections of a part of a screw, at the corresponding stages, numbered from 10 to 15,
inclusive.
In the several Figs. a indicates the body of the blank and the unthreaded part of
the screw, and p the pointed part of the blank and the screw. The groove, the
bottom of which forms the body of the threaded portion of the screw and the raised
part of the metal which finally forms the finished thread, is indicated by b.
A slight bur, which is formed on the raised portion of the metal as the rolling
progresses, and which disappears when the screw is finished, or in a subsequent
operation of cleaning, is indicated by c.
It will be observed by reference to Figs. 10 to 15 that the groove reaches its
maximum depth near the commencement of the operation, and that its width is
gradually increased until the thread is fully formed. The increasing width is also
shown in Figs. 4 to 9. It is also apparent from these Figs. that the width of the
raised portion of the metal is gradually reduced, and its height increased until the
thread is finally finished. This result is secured by the gradual and continued lateral
compression of the metal which forms the thread of the screw between the ribs of the
grooved dies as the blank is rolled, and which are narrow at the ends where they

page_text: commence to act upon the blank, so that they may be immediately forced into the
metal to the depth required for the body of the threaded part of the screw, and
which gradually increase in width to the opposite end of the die. Thus the ribs act
as wedges to compress the metal between them, and compel it to expand radially
from the blank and into the grooves of the dies.
At the end of the dies where the rolling commences, the grooves in the die will
be both wider and deeper than the thread to be produced, and the raised metal will
not fill the grooves; but they grow narrower and shallower as the opposite end is
approached, until they become near the end the exact counterpart of the thread to be
produced.
The above named Harvey has described in a U. S. patent, granted to him
January 3d, 1882, and numbered 251,874, a circular rotating die, which acts in
connection with a concave stationary die, to raise the thread described by him; but I
prefer to make my dies straight, and to give to one of them a reciprocating motion
past the other, which is stationary.
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 :-
A screw having a solid thread raised from the body of the blank by rolling it
between dies, which compress laterally the metal to form the thread, and force it to
expand radially from the blank into grooves in the die, having a form, transversely,
the counterpart of that to be given to the thread.
Dated the 20th day of May 1889.
CHARLES DAKE ROGERS.