Improvements in Wood-screws.
Year: 1893

page_text: Date of Application, 14th Mar., 1893-Accepted, 29th Apr., 1893
3
COMPLETE SPECIFICATION.
[Communicated from abroad by MORRIS HERZBERG, of Chambers County,
Alabama, and THOMAS L. NORMAN, of West Point, Troup County, Georgia,
both in the United States of America, Inventors.]
Improvements in Wood-screws.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, 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 as above stated to wood screws having reference to pro-
viding a self-countersinking element therefor, which shall not increase the manufac-
turing cost therefor and also oue that will properly perform the said operation, and
at the same time provide a suitable bearing surface on the wood and a bearing
surface on iron plates, either of which shall be as good as in an ordinary screw, the
details of all of which will be hereinafter fully specified.
The accompanying drawings illustrate the invention in Figure 1 in perspective
and in Figure 2 in section, the former showing the device complete and the latter
being a section through the head showing the preferable form of the grooves.
Corresponding reference marks designate like parts in both figures.
In these drawings a is the screw and bare grooves which are cut on the under
side of the head in the manner and for the purpose as hereinafter specified. Upon
reference to Figure 2 of the drawings it will be seen that these grooves have sides
about perpendicular, that is, as near so as it is practicable to make them, and that
they are cut in the under side of the head in such a manner as to not disturb the
general conicality or in other words the continuity of bearing of the conical head
any more than is absolutely necessary. It will also be seen on reference to Figure 1
that these grooves depart from the radial in both directions, that is, that they
extend across the conical part of the head in tangential direction and that they are
so arranged as to intersect and form diamond and rhomboidal sections between them
having parting corners and sides 6 inclined to the direction of the motion of the
screw in turning into place.
All woods are more or less soft and elastic and hence the grooves b will fill with
the wood fibre as soon as the screw reaches its bottoming point, abrading and
gathering same as it is forced into place, the corners b' and the edges 62 materially
aiding in this abrasion. This filling up of the said grooves with wood, which is of
course compressed into a hard state, provides the best possible frictional bearing for
the head of the screw on a wood surface, while from the fact that there is no pro-
jection beyond the general level of the surface of the head, said head will find a
good bearing on an iron surface, such as the countersinks in builders' hardware and
analogous metallic articles.
This device when once run to its proper depth stops as the grooves are filled
with compressed wood and will cut no more, hence any screw once settled in place
may be removed and reinserted without countersinking deeper in "turning down
hard" again. These grooves do not materially weaken the head, and in it there is
a solid smooth bearing when inserted that does not break the grain or sink into the
wood under strain on the screw.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondents I declare that what I claim is-
A wood screw having on the under side of its head two sets of narrow, inclined
grooves, said grooves crossing each other and the grooves of one set being

page_text: inclined in an opposite direction to those of the other set, substantially as
-described.
Dated this 14th day of March 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.