IMPROVEMENTS IN SCREW CUTTING MACHINERY AND TOOLS
Year: 1876

page_text: LETTERS PATENT to Edmond Pierre Baville, of Passy, France, but at present
residing at Leeds, in the County of York, and Arthur Greenwood, of Leeds
aforesaid, for the Invention of "IMPROVEMENTS IN SCREW CUTTING MACHINERY
AND TOOLS."-
Sealed the 15th May 1877, and dated the 28th November 1876.
PROVISIONAL SPECIFICATION left by the said Edmond Pierre Baville and
Arthur Greenwood at the Office of the Commissioners of Patents on the 28th
November 1876.
EDMOND PIERRE BAVILLE, of Passy, France, but at present residing at Leeds,
in the County of York, and ARTHUR GREENWOOD, of Leeds aforesaid. IMPROVE
MENTS IN SCREW CUTTING MACHINERY AND TOOLS."
This Invention relates, firstly, to an improved construction of tool or cutter for
cutting the threads of screws; and secondly, to means for presenting the cutter to
its work.
Hitherto in cutting screws in dies the action has been rather to indent or impress
the screw thread than to cut away the superfluous metal.
Instead of using segment-shaped cutting dies as hitherto for cutting screws we
form our cutting tool from a cross section of a steel cylindrical screw or threaded
plug, channelling it transversely of the thread to convert it into, say, four distinct
cutters, each of which will possess two cutting edges. The tool thus formed,
supposing it to be applied to a screw stock, we drop into it a slot or recess made
in the stock, and having the counterpart shape of the tool. This recess or slot is so
situate with regard to the work to be threaded that one cutter of the four will
project into the central space that the work is to occupy, and is so arranged
relatively to a central line down through the stock that the cutter will always be
presented to the work in the best possible position for working, that is to say,
instead of pressing out or indenting the thread as the work is forced into contact
therewith it will form the thread by a clean cut or removal of the metal like
the cutting tool of a lathe.
The cutter is secured in the stock by means of a transverse pin, the withdrawal
of which will permit of the cutter being shifted to bring a fresh cutting edge into
action.

page_text: The work may be pressed up to the cutter by a threaded semicircular rest. This
arrangement will serve for the fitting of screw stocks that are to be used for
common work.
For cutting screws of better class we prefer to use in one stock three tools
such as that described. Two of these we fit into slots or recesses in radial sliding
plates, and the third in a recess made in the stock, which recesses will serve to
hold the tools in the desired position and angle for operating most efficiently on
the work. The plates slide in radial slots made in the stock, and they are them-
selves slotted transversely to receive the diagonal or diverging prongs of an
adjustable cross head, the advance of which by means of an adjustable screw will
move the cutter inwards towards their work.
In applying these cutters to screw cutting machines we fit them to radial sliding
plates, as above described, and mount these plates in radial slots in the head or
mandril.
On either side of the slotted portion of the head a circular plate is fitted;
the outer plate is flanged, and forins a cap piece to the head. These plates arc
connected together by screw bolts, which pass from one plate to the other externally
of the head. The sliding plates are each formed with a pair of studs, which enter
cain-shaped slots made in the circular plates in order that when an independent
axial motion is given to these plates the cutters may be advanced up to or with-
drawn from the work. The head of the screw cutting machine is made fast to the
driving spindle, and receives a rapid rotary motion therefrom, and thus the cutters
are caused to move around the work as it is presented to them.
The advance motion of the cutters is obtained from the axial motion of the
circular plates, which receives their supplementary or independant motion from a
finger attached thereto, and projecting into a cam slot of a sliding collar that
embraces the cutter head and rotates with it. This sliding collar is pressed forward
by the attendant bearing upon a forked leven, and the advance of the collar is
limited by a stop pin.
When preparing to cut a screw thread the attendant slides forward the collar
until it is arrested by the cutters coming in contact with a correctly cut screw, and
the same size as the one to be cut, which serves as a master piece to give the
diameter, and also adjusts the cutters to the correct lateral position. When these
are thus adjusted the stop pin of the collar is advanced into contact with the plate,
thus establishing the adjustinent for the diameter required to be screwed. The
attendant slides back the collar, the cam groove of which acting on the finger pro-
jecting from the circular plates will cause the cam grooves of those plates to draw
back the cutter slides and release the master picce from the cutters.
From the above explanation it will be understood that the diameter of the screw
to be cut is determined by the stop pin, the attendant always sliding the collar
forward as far as the stop pin will permit previous to making the cut.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edmond Pierre Baville and Arthur Greenwood in the Great Seal
Patent Office on the 28th May 1877.
EDMOND PIERRE BAVILLE, of Passy, France, but at present residing at Leeds,
in the County of York, and ARTHUR GREENWOOD, of Leeds aforesaid. "IMPROVE-
MENTS IN SCREW CUTTING MACHINERY AND TOOLS."
This Invention relates, firstly, to an improved construction of tool or cutter for
cutting the threads of screws; and secondly, to means for presenting the cutter to
its work.
Hitherto in cutting screws in dies the action has been rather to indent or impress
the screw thread than to cut away the superfluous metal.

page_text: Instead of using segment-shaped cutting dies as hitherto for cutting screws we
form our cutting tool from a cross section of a steel cylindrical screw tap or threaded
plug, channelling it transversely of the thread to convert it into, say, four distinct
cutters, each of which will possess two cutting edges.
In the accompanying Drawings we have shewn the improved cutting tool as
applied to a screw stock and also to a lathe head.
Fig. 1 is a side view of a screw stock fitted, according to my Invention, with
one of the improved cutting tools in place, and Fig. 2 is a longitudinal section of
the same.
In these Figures A is the screw stock or frame carrying the cutting tool (which
is shewn at B), and provided with handles as usual for moving it around the work
which is to be acted upon by the cutting tool. The breadth of the tool B is shewn
as equal to the thickness of the stock, but this is not necessary for the proper action
of the tool, although a good breadth is preferred, as it ensures the more steady
working of the screw stock. The tool B is fitted into a slot or recess made
transversely of the stock, and having the counterpart shape of the tool.
This recess
or slot is so situate with regard to the work to be threaded that one cutter of the
four will project into the central space that the work is to occupy, and it is so
arranged relatively to a central line drawn through the stock that the cutter will
always be presented to the work in the best possible position for working, that is
to say, instead of pressing out or indenting the thread as the work is forced into
contact therewith it will form the thread by a clean cut or removal of the instal
like the cutting tool of a lathe.
The cutter is secured in the stock by means of a transverse pin b, the withdrawal
of which will permit of the cutter being shifted to bring a fresh cutting edge into
action.
The work is pressed up to the cutter by a threaded semicircular rest c, which
slides in guides in the stock, and is connected by a dovetail joint to a threaded
socket D, into which fits a screw E made fast to or forming a portion of one of the
handles F, which is fitted loosely to the stock A, so that it may turn freely, and
thereby advance or draw back the slide rest C. This handle is secured to the stock
by means of a pin f, which enters an annular groove made in that portion of the
handle which enters the socket of the screw stock. When the work is inserted in
the stock, as at G, it is pressed up against the cutter B by the advance of the rest C,
and the stock being moved round the work in the usual manner, the cutter being
from time to time advanced until the required depth of cut is obtained, a clean cut
screw thread will be rapidly produced.
When the cutting edge has become dull the tool is shifted axially to bring the
several cutting edges in succession into action, and when the forward edges of the
four cutters have been thus used the tool is to be reversed, when four additional
cutting edges may in succession be brought into action.
The arrangement shown at Figures 1 and 2 will serve for the fitting of screw
stocks that are to be used for common work.
For cutting screws of a better class we prefer to use in one stock three tools,
such as that described. This arrangement is shewn in side view at Fig. 3, and in
cross section at Fig. 4, where A is the stock; B, B, B, are the cutting tools; and
C is the work to be threaded. Two of these tools B are fitted into slots or recesses
formed in radial sliding plates H, and the third is placed in a recess made in the
stock. These recesses will serve to hold the tools in the desired position and angle
for operating most efficiently on the work. The plates slide in radial slots made in
the stock, and they are themselves slotted transversely to receive the diagonal or
diverging prongs of an adjustable cross head I, which is threaded to receive a
screw E connected to or forming part of the loose handle F. By turning this
handle so that the screw E will force down the cross head the moveable cutters
will be advanced inwards towards the stationary cutter to take a hold on the work.
The cutters are severally secured in their recesses by means of transverse pins b.

page_text: In applying these cutters to screw cutting machines we fit them to radial sliding
plates, as above described, and mount these plates in radial slots in a head, which is
to be attached to the mandril of a lathe.
The mode of carrying out this part of our Invention is illustrated at Figures 5, 6,
and 7, Fig. 5 being a transverse section of the lathe head; Fig. 6, a plan view of
the same; and Fig. 7, an end view of the lathe head.
In these Figures A is the head attached to the mandril; B, B, B, are the cutters;
and C, C, C, are the radial sliding plates into which the cutters are fitted and keyed,
as before explained.
On either side of that portion of the head which is slotted to receive the sliding
plates C, C, C, an annular plate D is fitted; the outer plate is flanged, and forms
a cap piece to the head; the inner plate is formed with a hollow boss, and it is
divided through its centre to permit of its application to the head. Over the boss
a clip ring D* is slidden to hold the parts in place. These plates are connected
together by screw bolts d, which pass from one plate to the other externally of the
head. The radial sliding plates C are each formed with a pair of studs e, which
enter cam-shaped slots made in the circular plates D in order that when an inde-
pendent axial motion is given to these plates the cutters may be advanced up to or
withdrawn from the work. The head of the screw cutting machine is made fast
to the driver spindle E, and receives a rapid rotary motion therefrom, and thus
the cutters are caused to move around the work as it is presented to them.
The advance motion of the cutters is obtained from the axial motion of the
circular plates D, D, which receive their supplementary or independent motion
from an inclined finger F attached thereto, and projecting into a slot in a collar G,
such slot having a corresponding incline or divergence, from parallelism with
the axis of motion of the cutter head. This collar G embraces the cutter head and
rotates with it, it being connected to the head by means of ribs or feathers (, so
that it may slide freely thereon. This sliding collar is pressed forward by the
attendant bearing upon a forked lever, not shewn in the Drawing, and the advance
of the collar is limited by a stop pin g projecting therefrom and standing opposite
the inner plate D.
When preparing to cut a screw thread the attendant slides forward the collar G
until it is arrested by the cutters coming in contact with a correctly cut screw the
same size as the one to be cut, which serves as a master piece to give the diameter,
and also adjusts the cutters to the correct position. When these are thus adjusted
the stop pin g is advanced into contact with the plate D and made fast to the
collar G. This adjustment of the stop pin ensures the advance of the cutters to
the limit required for producing a screw of a diameter corresponding to that of the
master piece. The attendant then slides back the collar G, the cam groove of
which, acting on the finger F projecting from the circular plates, will cause the cam
grooves of the plates D to draw back the cutter slides and release the master piece
from the cutters.
From the above explanation it will be understood that the diameter of the screw
to be cut is determined by the stop pin, the attendant always sliding the collar
forward as far as the stop pin will permit when making the cut.
Having now set forth the nature of our Invention of " Improvements in Screw
Cutting Machinery and Tools," and explained the manner of carrying the same into
effect, we wish it to be understood that under the above in part recited Letters
Patent we claim,―
First. The reversible screw cutting tool B constructed with a series of cutting
edges, as above described.
Second. In combination with the screw cutting tool B a holder for the same,
consisting of a recess made in the stock in a sliding plate contained in the stock,
and so situate that the acting cutting edge of the tool shall coincide, or nearly so,
with a line radiating from the centre of the work to be threaded.
Third. The combination in a stock of three screw cutting tools, one set in a

page_text: fixed, and two in adjustable holders, the acting cutting edges of such tools coin-
ciding, or nearly so, with lines radiating from the centre of the work, as and for the
purpose above described.
Fourth. In combination with the screw cutting tools B mounted in radial sliding
plates C, C, fitted to the head A, the cam plates D for advancing and withdrawing
the cutters, such cam plates being actuated through a projecting finger F entering &
cam groove in the face of a sliding collar G.
In witness whereof, I, the said Arthur Greenwood, have hereunto set my hand
and seal, the Nineteenth day of May, in the year of our Lord One thousand
eight hundred and seventy-seven.
ARTHUR GREENWOOD. (LS.)