IMPROVEMENTS IN WOOD SCREWS, AND IN MACHINERY EMPLOYED IN THE MANUFACTURE THEREOF
Year: 1870

page_text: LETTERS PATENT to John Thomson King, of Liverpool, in the County
"
of Lancaster, Patent Agent, for the Invention of "IMPROVEMENTS IN
WOOD SCREWS, AND IN MACHINERY EMPLOYED IN THE MANUFACTURE THEREOF.'
-A communication from abroad by George Colin Davies, of Dayton,
in the State of Ohio, one of the United States of America.
Sealed the 27th June 1871, and dated the 28th December 1870.
PROVISIONAL SPECIFICATION left by the said John Thomson King
at the Office of the Commissioners of Patents, with his Petition,
on the 28th December 1870.
I, JOHN THOMSON KING, of Liverpool, in the County of Lancaster,
Patent Agent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN WOOD SCREWS, AND IN MACHINERY EMPLOYED IN THE MANU-
FACTURE THEREOF," the same being a communication to me from abroad by
George Colin Davies, of Dayton, in the State of Ohio, one of the United
States of America, to be as follows :-
The various kinds of wood screws heretofore made have had from their
form and necessary mode of manufacture some of the following dis-

page_text: advantages:-(1), they have been liable to break where the shank and
core merge into each other; (2), the pitch or distance between the
threads has not been uniform; and, (3), the core has been of less
diameter at about the middle of its length than at the ends.
The object of the said Invention is to provide merchantable wood
screws without the defects above set forth, possessing the special advan-
tages now to be mentioned: (a), they can be driven easily into wood
with little or no previous hole; (b), the point being always truly axial
they can always be driven in the direction in which they are started;
(c), the core provides the maximum strength at the point where it is
most required.
For these amongst other purposes wood screws are manufactured or
constructed, first, by making the core of a conoidal or taper outline from
neck to point, and forming on, around, or with the said core a helix or
thread of uniform pitch, and of uniform external diameter until it nears
the point where it dies out; second, in combination in screws each
with the aforesaid core tapering from its base to its point, and with
threads of equal pitch and equal external diameter, except near the
point forming the entering end into a so-called central point; third, in
combination with the aforesaid tapering core with threads constructed
as described under the above first and second heads forming the holding
edges of the helices of such screws at a greater angle to the line of the
axis of the core than the leading edges of such helices; by leading edges
I mean the edges which first enter the wood when a screw is being
driven.
The machinery by which the production of wood screws with the
above features of novelty is rendered successful, consists of apparatus or
a machine having automatic movements at certain intervals of time for
forming the taper core, the threads, and the points. It consists essentially
of a revolving spindle fitted with jaws or nippers for holding the screw
blank and of a cutting tool and cutting tool holder. To the cutting tool
holder which is free to be moved on a longitudinal axis two principal
motions are imparted by cams or their equivalents; these are, first, a
lateral motion in the direction of the axis of the screw blank, and, second,
a motion at the cutting tool end perpendicular to the axis of the screw
blank. The lower end of the said cutting tool holder has a curvilinear

page_text: piece which bears against a cam, whose function it is to advance the
cutting tool for every new cut until the required helical groove has been
formed.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Thomson King in the Great Seal Patent
Office on the 28th June 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
THOMSON KING, of Liverpool, in the County of Lancaster, Patent
Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-eighth day of December, in the
year of our Lord One thousand eight hundred and seventy, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Thomson King, Her special
licence, that I, the said John Thomson King, my executors, adminis-
trators, and assigns, or such others as I, the said John Thomson
King, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN WOOD SCREWS, AND IN MACHINERY EMPLOYED IN THE MANU-
FACTURE THEREOF," a communication to me from abroad by George Colin
Davies, of Dayton, in the State of Ohio, one of the United States of
America, upon the condition (amongst others) that I, the said John
Thomson King, my executors or administrators, by an instrument in
writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Thomson King, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in

page_text: and by the following statement, reference being had to the accom-
panying Sheet of illustrative Drawings, and to the figures and letters
marked thereon, that is to say :-
The various kinds of wood screws heretofore made have had from their
form and necessary mode of manufacture some of the following dis-
advantages:-(1), they have been liable to break where the shank and
core merge into each other; (2), the pitch or distance between the
threads has not been uniform; and (3), the core has been of less diameter
at about the middle of its length than at the ends.
The object of the said Invention is to provide merchantable wood
screws, without the defects above set forth, possessing the special
advantages now to be mentioned: (a), they can be driven easily into
wood with little or no previous hole; (b), the point being always truly
axial they can always be driven in the direction in which they are
started; (c) the core provides the maximum strength at the point where
it is most required.
For these amongst other purposes wood screws are manufactured or
constructed, first, by making the core of a conoidal or taper outline from
neck to point, and forming on, around, or with the said core a helix
or thread of uniform pitch and of uniform external diameter until it
nears the point where it dies out; second, in combination in screws each
with the aforesaid core tapering from its base to its point and with
threads of equal pitch and equal external diameter except near the
point forming the entering end into a so-called central point; third,
in combination with the aforesaid tapering core with threads constructed
as described, under the above first and second heads, forming the
holding edges of the helices of such screws at a greater angle to the
line of the axis of the core than the leading edges of such helices; by
leading edges I mean the edges which first enter the wood when a
screw is being driven.
The machinery by which the production of wood screws with the
above features of novelty is rendered successful, consists of apparatus
or a machine having automatic movements at certain intervals of time
for forming the taper core, the threads, and the points. It consists
essentially of a revolving spindle fitted with jaws or nippers for holding
the screw blank and of a cutting tool and cutting tool holder. To the
cutting tool holder which is free to be moved on a longitudinal axis two

page_text: principal motions are imparted by cams or their equivalents. These
are, first, a lateral motion in the direction of the axis of the screw blank;
and second, a motion at the cutting tool end perpendicular to the axis
of the screw blank. The lower end of the said cutting tool holder has
a curvilinear piece which bears against a cam whose function it is to
advance the cutting tool for every new cut until the required helical
groove has been formed.
On the Sheet of Drawings which accompany this, Fig. 1 is a side
elevation of a screw in accordance with the above-mentioned first and
second features of novelty. It has been drawn to an enlarged scale to
distinctly shew the several portions, and has been shewn with a cylin-
drical shank, as that is the form ordinarily preferred, although it might
be of a form tapering from the head, or partly parallel and partly
tapering, or otherwise. a denotes the core, this merges into the shank
at 6 and terminates in a point at c; d, helix of uniform pitch and
diameter from 6 to e, and of gradually decreasing diameter from e to
the point; d joins the apex or point of the conoidal core in this view,
and so forms a so-called central point under the above second feature of
novelty; d may die out before reaching the apex of the core, as
shown in Fig. 2; f, shank; 9, head, here shewn of the common form.
It will be evident it may be of hemispherical, cylindrical, or other
form.
Fig. 2 is a side elevation of a screw drawn to an enlarged scale, the
better to illustrate the above-mentioned third feature of novelty. Here
h is the conoidal or taper core; i, the helix, the holding edges of which
stand at a greater angle to the line of the axis of the core than the
leading edges; j, shank; k, head. The helix i dies out before it reaches
the point of g, hence this Figure illustrates the third part in combination
with the first part. When the helix h is carried to the apex of g,
as shewn in Fig. 1, a combination of the third and second parts is
effected.
That others may be enabled to manufacture or produce wood screws
possessing the novel features above referred to, the mechanism devised
and perfected for the purpose will now be described.
Fig. 3 is a front view; Fig. 4*, side or end view. Like letters refer to

page_text: The essential parts of this machine consist of a revolving spindle,
fitted with jaws or nippers B for holding the screw blank while being
chased or threaded; a slide H with brackets or lugs fitted to the top of
the table K by slides or dovetails so as to have a reciprocating lateral
motion in the direction of the axis of the spindle, which motion is given
by a cam or excentric; a lever G suspended between the lugs of the
slide H by the pin I so as to have a free motion perpendicular to the
axis of the spindle, and a revolving cam or excentrically toothed
wheel M, the whole being geared together so as to move automatically
at certain intervals of time. The head of the lever G is provided with
a cutting tool or chaser C held in place by the flat headed bolt D, F,
and nut E. The lower end of the lever G is fitted with a peculiarly
shaped piece of metal L called a shaper or former. The central portion
of this shaper L is a tangent to the shaft N, while the point or lower
part approaches that of a circle. Near the centre of the lever G is a
spiral spring O for the purpose of holding the shaper L firmly against
the teeth and face of the cam M.
The operation of the machine is very simple, rotation being given to
the spindle and nippers by a belt or gearing, the screw blank A is fed
into and nipped by the nippers B by any suitable device used for that
purpose. The motion of the spindle is communicated to the shaft N
and cam M. The teeth m² acting in the former L brings the chaser
or cutting tool in contact with the blank A, revolving at a suitable
velocity. At the same time motion in the direction of the axis of the
blank being given to the slide H, the cutting tool is carried towards the
point of the revolving blank, cutting from its outer surface a spiral
ribbon of such pitch and depth as may be desired. The cutter on
reaching the point of the blank is suddenly drawn back by the passing
of the tooth m below the point of the former L and the action of the
spring O. At the same time the slide H is drawn back to its former
position, so that when the second tooth of the cam M is brought in
contact with the former or shaper L the cutter C is in position to
commence a second cut, the depth of each cut being regulated by the
excentricity of the teeth of the cam M. The cuts however are modified
by the peculiar form of the shaper L which gives the taper or conical
shape to the core of the screw. Were the face of the shaper L an arc
of a circle it is evident that the
core formed by it would be nearly

page_text: straight, that is having parallel sides as in the ordinary form of wood
screws, for it will be apparent that as the blank revolves and the chaser
moves from the shank A¹ towards the point with a motion corresponding
with the pitch of the screw to be made, and being forced against the
blank by the teeth m¹ acting on the shaper L and lever G, a spiral cut
will be made the whole length of the blank, but of increasing depth as
it approaches the point of the blank in consequence of the curved form
of the lower part of the shaper L, which is the last point acted upon by
the teeth m in their revolution in the direction of the arrow.
The cam
or excentric M is so timed in its revolution as to give one tooth for each
traverse of the chaser from the shank A¹ to the point of the blank,
and each following tooth is as much higher than its predecessor as is
necessary to give the chaser the proper depth of each cut.
The construction of these threading machines is not necessarily strictly
in conformity with the Drawings here given, but with such modifi-
cations and equivalent movements of parts as will fully insure the
cutting or chasing the threads on wood screws, in such a manner as to
produce a core, or central solid part of a taper, or conical form as set
forth herein.
Having now particularly described my said Invention, and set forth
means whereby the same may be carried into effect, so as thereby to
introduce into the realm a new manufacture, I claim the right to make,
use, exercise, and vend the wood screws and machinery employed in the
manufacture thercof, substantially as herein described and illustrated on
the Drawings.
In witness whereof, I, the said John Thomson King, have hercunto
set my hand and scal, the Twenty-sixth day of June, in the year
In the presence of,
R. E. GIBSON.
J. T. KING.
(L.S.)