IMPROVE- MENTS IN MACHINERY FOR CUTTING THE THREADS OF WOOD SCREWS
Year: 1858

page_text: LETTERS PATENT to George Tomlinson Bousfield, of Loughborough
Park, Brixton, in the County of Surrey, for the Invention of "IMPROVE-
MENTS IN MACHINERY FOR CUTTING THE THREADS OF WOOD SCREWS."-A
communication from New York, United States of America.
Sealed the 25th March 1859, and dated the 15th October 1858.
PROVISIONAL SPECIFICATION left by the said George Tomlinson
Bousfield at the Office of the Commissioners of Patents, with his
Petition, on the 15th October 1858.
I, GEORGE TOMLINSON BOUSFIELD, of Loughborough Park, Brixton, in the
County of Surrey, do hereby declare the nature of the Invention for "IM-
PROVEMENTS IN MACHINERY FOR CUTTING THE THREADS OF WOOD SCREWS," to be as
follows:-1
The Invention has reference to that class of machines by means of which
the thread is cut upon wood screws by a chasing tool, which removes suc-
cessive shavings of metal, in contradistinction to machines in which the screw
is cut. by means of dies; it has heretofore been customary to cut wood screws
tapering at the point and tapering also where the core vanishes into the stem
of the screw by means of a single chasing tool, whose profile. determines the
form of the core and threads, and which is advanced more or less towards the
axis of the screw while the latter is being cut, as it is desired to make the
extremities of the core more or less tapering. In this mode of cutting screws
the tapering portion of the screw, and the body thereof between the tapering
portions are cut by the same cutting edge, and hence the profile of the tapering

page_text: portions of the screw is the same as that of the body thereof, but of greater or
less depth, and the core of the screw vanishes into the stem thereof, and
tapers to a point in the form of a volute, the profile of whose convolutions are
parallel with those of the core at the body of the screw between the tapering
portions.
The object of this Invention is to produce wood screws tapering with a
slope at the point, and tapering with a slope also where the core vanishes into
the stem of the screw, so that the profiles of the convolutions of the tapering
portions shall slope towards the point, and be inclined to those of the core at
the body of the screw between the tapering portions thereof.
The Invention consists in cutting the thread of such screws by means of
two cutting edges upon the chasing tool or tools, which edges are caused by
suitable mechanism to operate successively upon the screw, the one edge
having a form adapted to cutting the thread upon the body of the screw
between the sloping extremities of the core, and the other cutting edge having
a form adapted to cutting the thread upon the sloping extremities-of the core.
The Invention may be adapted to machines now in use for cutting wood
screws; the arrangement which I prefer is as follows:-The screw blank is
griped in a tubular holder which has an opening in its extremity, of &
suitable size and form to hold the screw blank firmly; it is maintained in the
holder by means of a sliding bolt, whose extremity terminates in a tongue, which
fits into the nick in the head of the screw blank, so as to cause it to revolve
upon its axis with the holder in which it is griped. The stem projects from
the holder, and is received into a rest, which is lined with a steel tube having
an opening at its side to permit the cutting tool to act upon the screw blank.
The tool is secured in a tool post, which is caused by suitable mechanism to
carry the tool lengthwise to and fro along the screw blank, and also to advance
it crosswise towards the axis thereof, and to withdraw it therefrom while the
screw is revolving in the rest. These movements may be imparted to the
tool post by means of cams operating upon a shaft to which the tool post is
secured, or otherwise. The screw, tool, or cutter may be of a single piece
of metal, which has a curved form longitudinally, while its cross section
is adapted to the size and peculiar form of the screw to be cut. The
cutting edge of this tool consists of a combination of two cutting edges, one
of these cutting edges has a profile, which is the counterpart of that of the
body of the screw between the sloping extremities of the threaded portion, the
other cutting edge has a profile, which is the counterpart of that of the sloping
portions of the screw. When the screw cutting machine, with this tool, is in
operation, screw cutting is commenced at the part. of the thread nearest the

page_text: head of the screw, by advancing the tool against the screw blank, and carrying
it longitudinally therewith while the screw blank is turned. When the tool
has been carried longitudinally past the point of the screw blank, its edge is
withdrawn from the screw blank, and it is carried back by the tool holder to
the position whence it started. It is then advanced again a little further than
at first against the screw blank, and carried lengthwise therewith as before;
and these operations are repeated a greater or less number of times according
to the dimensions of the screw, until the thread is cut to the required depth.
Though a single tool or cutter is above described and recommended, the
proper cutting edges may be on two or more pieces.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Tomlinson Bousfield in the Great Seal Patent
Office on the 15th April 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
TOMLINSON BOUSFIELD, of Loughborough Park, Brixton, in the County of
Surrey, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of October, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said George Tomlinson Bousfield, Her special licence that I, the
said George Tomlinson Bousfield, my executors, administrators, and assigns;
or such others as I, the said George Tomlinson Bousfield, my executors,
administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter 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 MACHINERY FOR CUTTING
THE THREADS OF WOOD SCREWS," a communication from New York, United
States of America, upon the condition (amongst others) that I, the said George
Tomlinson Bousfield, 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.

page_text: NOW KNOW YE, that I, the said George Tomlinson Bousfield, 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 and by the
following statement thereof, that is to say :-
The Invention has reference to that class of machines by means of which
the thread is cut upon wood screws by a chasing tool, which removes suc-
cessive shavings of metal, in contradistinction to machines in which the screw
is cut by means of dies; it has heretofore been customary to cut wood screws
tapering at the point, and tapering also where the core vanishes into the stem
of the screw, by means of a single chasing tool, whose profile determines- the
form of the core and threads, and which is advanced more or less towards the
axis of the screw while the latter is being cut, as it is desired to make the
extremities of the core more or less tapering. In this mode of cutting screws
the tapering portions of the screw and the body thereof between the tapering
portions are cut by the same cutting edge, and hence the profile of the
tapering portions of the screw is the same as that of the body thereof, but of
greater or less depth, and the core. of the screw vanishes into the stem thereof,
and tapers to a point in the form of a volute, the profile of whose convolutions
are parallel with those of the core at the body of the screw between the
tapering portions.
The object of this Invention is to produce wood screws tapering with a
slope at the point, and tapering with a slope also where the core vanishes into
the stem of the screw, so that the profiles of the convolutions of the tapering.
portions shall slope towards the point, and be inclined to those of the core at
the body of the screw between the tapering portions thereof.
The Invention consists in cutting the thread of such screws by means of
two cutting edges upon the chasing tool or tools, which edges are caused by
suitable mechanism to operate successively upon the screw, the one edge
having a form adapted to cutting the thread upon the body of the screw.
between the sloping extremities of the core, and the other cutting edge having
a form adapted to cutting the thread upon the sloping extremities of the core.
The Invention may be adapted to machines now in use for cutting wood
screws. The arrangement which I prefer is as follows:-The screw blank a
is griped in a tubular holder D, which has an opening in its extremity of a
suitable size and form to hold the screw blank firmly; it is maintained in the
holder by means of a sliding bolt i, whose extremity terminates in a tongue,
which fits into the nick in the head of the screw blank, so as to cause it to
revolve upon its axis with the holder in which it is griped. The stem projects
from the holder, and is received into a rest U, which is
lined with a steel

page_text: tube h, having an opening at its side to permit the cutting tool to act upon
the screw blank. The tool E is secured in a tool post T, which is caused by
suitable mechanism to carry the tool lengthwise to and fro.along the screw,
and also to advance it crosswise towards the axis of the screw, and to withdraw
it therefrom while the screw is revolving in the rest. These movements may
be imparted to the tool post by means of cams operating upon the shaft F, to
which the tool post is secured, or otherwise. The screw tool or cutter may bé
of a single piece of metal,. (see Figures 1, 2, and 3,) which has a curved form
longitudinally, while its cross section is adapted to the size and peculiar form
of the screw to be cut. The cutting edge of this tool, as shown at Figure 4,
consists of a combination of two cutting edges e and e³ adjoining, at the dotted
line X, X; one of these cutting edges e has a profile, which is the counterpart
of that of the body of the screw between the sloping extremities of the threaded
portion, as shown at Figure 4, the other cutting edge e' has a profile, which is
the counterpart of that of the sloping portions of the screw, as shown at Z, Z',
Figure 4. In order to form such tools, I construct a ring of square steel, and
turn it truly in a turning lathe, the profile of the exterior being determined for
each size and denomination of screw by means of a suitable template; the
ring is then cut into. segments of convenient length, each of which constitutes
a tool, and the cutting edge is produced by grinding off one of the ends of the
tool to a suitable cutting angle. When the screw-cutting machine,. with this
tool, is in operation, screw cutting is commenced at the part of. the thread
nearest the head of the screw by advancing the tool against the screw blank,
and carrying it longitudinally therewith while the screw blank is turned.
When the tool has been carried longitudinally past the point of the screw
blank its edge is withdrawn from the screw blank, and .it is carried back by
the tool holder to the position' whence it started; it is then advanced again a
little further than at first against the screw blank, and carried lengthwise
therewith as before; and these operations are repeated a greater or less
number of times according to the dimensions of the screw until the thread is
cut to the required depth. When the cutter is first brought into contact with
the screw blank, the sloping cutting edge e¹ acts as shown at Z, Figure 4, and
as at this time the cutter is advanced against the blank simultaneously with
its longitudinal movement, the taper at the upper end of the screw is made
gradual: While the cutter is operating upon the body of the screw between
the sloping portions, the square cutting edge e acts as shown at Y, Figure 4,
and the sloping edge is inoperative. When the cutter is operating at the end
of the screw blank, the tool is again advanced towards the axis of the blank as
it is moved lengthwise therewith, so that the sloping cutting edge which

page_text: follows the square edges comes into action, as shown at Z, Figure 4,
and forms the tapering point with a suitable slope. The two cutting edges
thus act in succession upon the screw blank, remove the superfluous material,
and cut the thread, imparting to the screw at the same time the desirable
sloping form.
In the foregoing description I have described the improvement as embodied
in a single tool formed of one piece of metal; but it is obvious that the
Invention is not limited to this particular construction of tools; thus, for
example, the two cutting edges and may be formed upon two distinct
pieces of metal, and these two may be screwed side by side in a single tool
post, so as to constitute a compound tool, whose members meet at the dotted
line X, X; or each piece or sectional tool thus formed may be fixed in a
separate tool post, to which suitable motion may be imparted to cause the
sectional tools to act at proper times upon the revolving screw blank, so that
they do not interfere with each other; in this latter case the sloping cutting
edge e may be made to operate at the point of the screw only if a screw
sloping only at the point is required to be formed. I also have described the
tool as curved longitudinally, and I prefer to make it in this form, as it-
permits it to be adjusted more readily in the machine as it is worn away by
grinding; but the tool may be male straight, longitudinally, if the machine in
which it is to be used is adapted to a tool of such longitudinal form.
What I claim as the Invention, and desire to secure by Letters Patent is,
the cutting of the threads of wood screws by means of chasing tools, whose
cutting edges have profiles, which are respectively counterparts of the body
and sloping portions of the screws, and which are caused to act in succession
upon the screw blank.
In witness whereof, I, the said George Tomlinson Bousfield, have here-
upto set my hand and seal, this Fifteenth day of April, in the year of
our Lord One thousand eight hundred and fifty-nine.
Witness,
W. S. HARRISON,
New Court, St. Swithin's Lane,
London.
GEO. T. BOUSFIELD. (L.S.)