IMPROVEMENTS IN APPARATUS FOR CUTTING OR FORMING SCREW THREADS UPON WOOD, METAL, AND OTHER MATERIAL
Year: 1872

page_text: LETTERS PATENT to Charles Dumbleton, of Catisfield House, Fareham,
in the County of Hants, Colonel in Her Majesty's Army, for the
Invention of "IMPROVEMENTS IN APPARATUS FOR CUTTING OR FORMING
SCREW THREADS UPON WOOD, METAL, AND OTHER MATERIAL."
Sealed the 4th June 1872, and dated the 19th March 1872.
PROVISIONAL SPECIFICATION left by the said Charles Dumbleton at
the Office of the Commissioners of Patents, with his Petition, on
the 19th March 1872.
I, CHARLES DUMBLETON, of Catisfield House, Fareham, in the County
of Hants, Colonel in Her Majesty's Army, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN APPARATUS FOR CUTTING OB
FORMING SCREW THREADS UPON WOOD, METAL, AND OTHER MATERIAL," to be as
follows:-
This Invention relates to apparatus for cutting or forming screw
threads upon the outside or the inside of wood, metal, and other
material.

page_text: The apparatus consists principally of a shifting holder to which the
piece of wood or other material is to be secured; the holder having a
cone or shaped head for the purpose. A portion of the holder or the
stem thereof is threaded, and this portion is caused to travel to bring the
piece of, say, wood, into contact with a revolving cutter which may be
driven from an overhead pulley or otherwise. The cutter and its frame
are adjustable so that the cutter can be arranged nearer to or farther
from the centre to permit of varying sized pieces of wood being operated
upon. The cutter frame is in some cases fitted upon pivots to determine
the depth to which the cutter shall act, this being under the direction
of the attendant or adjustable by meclianical means as found convenient.
The holder and also the revolving cutter are removable so that others
can be placed in for cutting different shaped threads.
The apparatus is applicable to ordinary lathes or turning machines
or it may have special frames provided for it.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Dumbleton in the Great Seal Patent Office
on the 19th Septenīber 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES.
DUMBLETON, of Catisfield House, Farcham, in the County of Hants,
Colonel in Her Majesty's Army, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Nineteenth day of March, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Charles Dumbleton, Her special licence
that I, the said Charles Dumbleton, my executors, administrators, and
assigns, or such others as I, the said Charles Dumbleton, 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
APPARATUS FOR CUTTING OR FORMING SCREW THREADS UPON WOOD, METAL, AND.

page_text: OTHER MATERIAL," upon. the condition (amongst others) that I, the said
Charles Dumbleton, 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 Charles Dumbleton, do hereby declare
the nature of my 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, reference being had to the Drawings
hereunto annexed, that is to say :-
This Invention relates to apparatus for cutting or forming screw
threads upon the outside or the inside of wood, metal, and other such
like material.
The apparatus consists according to one method of a shifting or
movable stem to be attached to a piece of wood or other material upon
which a screw thread has to be cut, the stem having a cone or shaped
head for the purpose. A portion of a holder socket is threaded, and this
portion with the holder is caused to travel on the cone headed stem to
bring a revolving cutter into contact with the piece of, say, wood,
the revolving cutter being driven from an overhead pulley or other-
wise. The cutter and a frame in which it is fitted are adjustable in
the holder, so that the cutter can be arranged nearer to or farther
from the centre to permit of varying sized pieces, of wood being
operated upon. The cutter frame is in some cases fitted upon pivots
to determine the depth to which the cutter shall act, this being under
the direction of the attendant, or it may be adjustable by mechanical
means as found convenient. The holder and also the revolving cutter
form one apparatus and are removable, so that others can be placed in
for cutting different shaped threads or different shaped cutters can be
fitted on its spindle as desired.
A method of using the tool is thus, let it be required to cut an outside
thread. Prepare the work to, the diameter required, the back centre
of the lathe being removed and the material being held in the chuck
alone in the centre of the work, turn a conical recess into which the
left end of the lead screw with its jagged or even square or other
angular shaped head shall with pressure from the back centre now

page_text: applied fit so tight that as the mandril is turned by hand, being released
of its bands, the work shall carry the lead screw with it, the frame
carrying the cutter from its own weight will hang below the leading
screw; the frame is now brought to an upright position and the
catgut from the overhead motion applied to the pulley, thus holding
the entire tool in the position used when in operation by the pressure
screw at top of the frame, the cutter is now adjusted to the depth of
thread required, and with the left hand turning the mandril the cutter is
brought to approach the work, the overhead or corresponding driving
gear is at the same time set in motion and driving the pulley carrying
the cutter, the thread is formed as the left hand gives motion to the
mandril and lead screw.
The method of forming an inside screw is almost similar to that
described. The instrument is set in the same manner excepting the
upper edge of the circular cutter is brought in contact in the inside
of the work.
The apparatus is applicable to ordinary lathes or turning machines
of the most simple form, and can also be applied for cutting screws
instead of the present complicated mechanism necessary for the purpose.
It can also be fitted to the ordinary cutting lathe, the cutter apparatus
being mounted in prongs, and held in the slide rest as are ordinary
tools.
The Invention will be understood. by reference to the accompanying
Drawings.
Figure 1 is a face, and Figure 2 a side view of an apparatus such as I
have above described.
14
a is the holder, formed with a socket b for taking over a threaded
portion of a rod or stem c, one end of which is here shown to fit the
poppet screw d of an ordinary lathe head, as indicated more particularly
in Figure 3. The holder has a slot e in it for a reduced portion of a
block or cutter frame f to slide and be adjusted by the set screw g, the
block having a notch in it for the reception of a whorl or pulley h, whose
spindle i passes through the prongs or fork of the notch to hold it in
place, and to permit of it being rotated by a cord j from a band wheel
fitted above. The spindle of the whorl projects and it carries on its
free end a circular cutter k for forming the screw thread upon the
article, say a box / fitted upon the chuck m. The holder with the cutting.
appliance is arranged to move to and fro along the threaded portion of

page_text: •
the stem, and in its travel the cutters which are revolving cuts a thread
upon the article with a thread corresponding in pitch to that, upon
the stem, the shape of the thread being cut correspondingly to that of
the edge of the revolving cutter, and is not necessarily of the shape of
the thread upon the stem as indicated, an advantage of importance to
brass, and wood turners, when making articles composed of several pieces
of the same diameter but occupying different positions, as different shapes
of threads..can be cut at the same pitch, to prevent misplacement in
arranging the pieces it being only necessary to fit different shaped
cutters on to the spindles for each piece or change of thread required.
The cutter upon the projecting end of the spindle is shewn as forming
an exterior thread in Figure 3, but in Figure 4 I have shewn it as
cutting an interior one upon the article at the same pitch; but by
arranging different sized wheels between the lead screw c and the
article, various pitches of thread can be cut. The stem of the first form
of holder is cone shaped to bite the article firmly, and this arrangement
causes an adjustment of the apparatus after the article has been turned
down in the usual manner, but by the arrangement shewn at Figure 4
no adjustment is required other than that of throwing a set of wheels
into gear, and bringing down the holder to determine the depth of
thread. It will be understood by this Figure that the threaded stem
of the holder is mounted upon separate poppet heads, and its rotation
is caused through the pinion n taking into its toothed wheel p and
into that q on the lathe spindle, so that when the latter is turned by
hand or by an appliance the socket traverses along and the thread is
cut upon the article accordingly and corresponding in pitch as before
explained. In this case I propose to use an clastic or a weighted cord
to give rotation to the whorl of the cutter when the necessary tension
is put upon it by the descent of the holder upon the stem or lead screw
as a centre, and I regulate the depth to which the cutter shall enter
the material by a rest r, upon which the tool is free to lodge and slide,
the attendant simply holding the holder down upon the guide during
the operation.
In some cases for convenience I make the socket to fit over a threaded
collar, and be held secure by a pin or screw, as in Figure 5. By this
means the cutter and holder can be employed upon the collars of other
threaded stems or other holders and cutters can be fitted. upon it, to
obtain changes of pitch in the first case, and different shaped threads

page_text: in the other case. A view of the fork and whorl in section is shewn at
Figure 6, the whorl being fitted to touch to enable the spindle with the
cutter to be set nearer to or farther from the fork by slight blows on
either end: The cutters can be fitted into discs, and held by pins or
studs, or they may be formed by the same piece of metal as the discs
and ground up at the edges; some samples of these are shown in
Figure 7,
-
The cutter is capable of forming threads upon any diameter of
material notwithstanding the smallness of diameter of the threaded
stem, because one revolution of the stem is made to correspond to one
revolution of the article, consequently the pitch is the same upon both.
I do not limit myself to the form shown nor to the arrangement of
the parts, as they can be varied to suit the particular purpose for which
the cutting is effected, nor the attachment of it to any form of lathe
in or by which it is to be worked.
And having now described the nature of my said Invention, and in
'what manner the same is to be performed, I declare that I claim as
my Invention,
1
The improvements in apparatus for cutting screw threads substantially
as set forth.
Secondly. I claim the combination of a holder and a revolving cutter
with the appliances for obtaining a traversing motion for the purposes
described.
And, Thirdly. I claim the formation of various screw threads by moans
of revolving cutters fitted in a holder capable of sliding along a
threaded rod, as described and shewn.
In witness whereof, I, the said Charles Dumbleton, have hereunto
set my hand and scal, this Sixteenth day of September, in the
year of our Lord One thousand eight hundred and seventy-
two.
CHARLES DUMBLETON. (L.S.)
Colonel H.M. Indian Army.