I- PROVEMENTS IN DIES AND IN MACHINERY FOR CUTTING DIES AND TAPB
Year: 1868

page_text: LETTERS PATENT to George Tomlinson Bousfield, of Loughborough
Park, Brixton, in the County of Surrey, for the Invention of "I-
PROVEMENTS IN DIES AND IN MACHINERY FOR CUTTING DIES AND TAPB." A
communication from abroad by Benjamin Bee, residing at Harwich,
in the County of Barstable, State of Massachusetts, United States of
America.
Sealed the 2nd October 1868, and dated the 9th April 1868.
PROVISIONAL SPECIFICATION left by the said George Tomlinson
Bousfield at the Office of the Commissioners of Patents, with his
Petition, on the 9th April 1868.
I, GEORGE TOMLINSON BOUSFIELD, of Loughborough Park, Brixton, in
the County of Surrey, do hereby declare the nature of the said Invention
for: "IMPROVEMENTS IN DIES AND IN MACHINERY FOR CUTTING DIES AND TAPS,"
to be as follows:-
The Invention which constitutes the subject-matter of the present Patent
is divided into two parts, the first of which has reference to the con-
[Price &d.]
: :

page_text: struction of a die for screwing bolts, and the second consists of certain
improvements in machinery for cutting said improved dies and also
taps.
The improvement in dies consists in constructing the die with
iccentric threads, that is to say, with the curved lines of the screw
threads (that embrace the screw to be cut) eccentric to the axis of
the die and with the cutting edges nearest to the said axis, so that
when the die is used the parts of the screw threads which follow the
cutting edges diverge from the screw that is cut, and consequently
do not bind upon said screw and create friction. The profile of the
threads may be varied to suit the views of constructors, and the first
threads may be partially bevelled off, so that each successive cutting
edge that acts upon the bolt being cut removes a deeper clip than its
predecessor, the last threads of the die being of full size so as to finish
the bolt with a full threaded screw.
The object of the improvements in machinery which constitute the
subject-matter of the second part of the Invention is to enable dies
. and taps with eccentric threads to be cut with rapidity, economy,
and perfection. In such dies and taps the portion of the thread
extending backwards from each cutting edge towards the next suc-
ceeding cutting edge is eccentric to the axial line of the tap or die,
and the mechanism herein-after described cuts such eccentric threads
by means of a rotating cutter, which while revolving is caused to
approach and recede from the axial line of the blank as many times
as there are cutting edges to be made while the blank is turned upon
its axis and fed longitudinally past the position of the rotating cutter.
The blank so eccentrically cut is subsequently fluted longitudinally by
a milling or planing machine so as to produce cutting edges at the most
protuberant parts of the threads."
The said improvements comprise various new combinations of instru-
mentalities, the first of which consists of the combination of a rotating
mandril to hold and turn the blank, a vibrating rotating cutter to cut
the groove between the threads, a cutter arbor- inclined to the axis
of the rotating mandril (for the purpose of enabling the cutter to
cut an inclined thread), a feed screw or equivalent mechanism to
determine the pitch of the thread cut, and a regulating cam for
varying the position of the rotating cutter during the revolution of
the mandril, so as to impart the required eccentricity to the thread.

page_text: The special object of the second improvement in machinery.. is to
guide the portion of the cutter, that is operating upon the blank, so
that it may run truly notwithstanding the warped condition of the..
cutter produced by tempering or other causes. This improvement
consists of the combination of the rotating mandril for the blank with
a rotating cutter mounted upon an arbor that is free to play endwise in
its boxes with a guide for the side of the cutter to run against, and
with a spring (or its equivalent operating with a yielding pressure) to
keep the cutter constantly in contact with the guide, so that the guide
determines the position of the acting portion of the cutter in its
immediate vicinity.
.:
The special object of the third improvement in machinery. is to enable
the inclination of the cutter arbor to the axial line of the rotating
mandril and blank to be readily varied to adapt the machine to cutting
threads of different inclinations. This improvement consists of the
combination of the rotating mandril (for turning the blank) with the
arbor of the cutter, by means of a vibrating support for said arbor (or.
vibrating tool support as it will herein-after be called), and a moveable
centre block or its equivalent for changing-the-position of one or both
of the centres upon which the tool support vibrates, so that the inclina-
tion of the cutter arbor may be varied by varying the position of said
centre block or its equivalent.
The special object of the fourth improvement in machinery is to cause
the cutter to vibrate in accordance with the form of the regulating cam,
and also to prevent it from running into the metal too deeply. This
improvement consists of the combination of the rotating mandril and
rotating cutter with a cutter arbor inclined to the axial line of the
mandril, a regulating cam to determine the eccentricy of the cut made
and a weight (or its equivalent) operating antagonistically to the
cam to exercise a yielding pressure which causes the cutter arbor to,
vibrate in accordance with the form of the regulating cam, and at the
same time prevents the cutter from running into the work..
The special object of the fifth improvement in machinery is to enable
the rotating cutter to be readily set to its proper position, or at the
required distance from the axial line of the mandril and blank so that
taps of different sizes may be cut, and that cutters of different diameters
This improvement
may be used without changing the regulating cam.
consists of the combination of the rotating cutter and the regulating cam
"

page_text: (that regulates its position); by means of connecting mechanism whose
length is adjustable by means of a screw or its equivalent for that
purpose, so that the position of the rotating cutter relatively to the
regulating cam may be varied as required.
The special object of the sixth improvement in machinery is to cause
the rotating cutter to cut progressively nearer to the axial line of the
blank, as the blank is moved longitudinally past it so as to cut the
threads of tapering taps or dies. This improvement consists of the
combination of the regulating cam and the vibrating tool support with
a variable connecting or combining mechanism interposed between
the two, and a directing instrument for varying the effective length
of said connecting mechanism as required to cause the same pro-
tuberance of the regulating cam to move the cutter to different extents,
hence as the cutting proceeds, the cutter is not moved as near to the
axial line of the mandril and blank during one revolution of the
regulating cam as during the preceding revolution, so that the thread
cut is tapering although the protuberances of the cam do not vary.
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 8th October 1868.
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 Ninth day of April, in the year of
our Lord One thousand eight hundred and sixty-eight, in the thirty-
first 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

page_text: Invention for "IMPROVEMENTS IN DIES AND IN MACHINERY FOR CUITING DIES
AND TAPS," a communication to me from abroad by Benjamin Bee, a
person, resident at Harwich, in the County of Barstable, State of
Massachusetts, 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.
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, reference being had to the
accompanying Drawings, in which Figure 1 represents a plan of a
machine embodying the improvements in machinery; Figure 2 repre-
sents a front elevation of the same; Figure 3 a rear elevation of the
same; Figure 4 an end view of the same; Figure 5 an end view of the
same looking in a direction opposite to that in which Figure 4 was
taken; Figure 6 represents parts of the machine detached from the
remainder; Figure 7 represents a transverse section of a tap blank of full
size suitable for being cut in the machine; Figure 8 represents a section
of the same tap blank after being cut; Figure 9 represents a corre-
sponding section of the finished tap after it has been cut and fluted;
Figure 10 represents a transverse section of a die cut by the machine
and slotted for use; and Figure 11 represents a section of the same die at
its axis.
The Invention which constitutes the subject matter of the present
Patent is divided into two parts, the first of which has reference to
the construction of a die for screwing bolts, and the second. consists
of certain improvements in machinery for cutting said improved dies,
and also taps.
The improvement in dies consists in constructing the die with
eccentric threads, as represented at Figure 10, Sheet. 3, in the accom-
panying Drawings, that is to say, with the curved lines of the screw
threads a, a', (that embrace the screw to be cut) eccentric to the axis
of the die, and with the cutting edges a nearest to the said axis, so that

page_text: when the die is used the parts of the screw threads which follow the
cutting edges diverge from the screw that is cut, and consequently do
not bind upon said screw and create friction. The profile of the threads
may be varied to suit the views of constructors, and the first threads
may be partially bevelled off, as seen in section in Figure 11, Sheet 3,
so that each successive cutting edge that acts upon the bolt being cut
removes a deeper chip than its predecessor, the last threads of the die
being of full size so as to finish the bolt with a full threaded screw.
The object of the improvements in machinery which constitute the
subject-matter of the second part of the Invention is to enable dies and
taps with excentric threads, such as are represented at Figures 9, 10,
and 11 of the accompanying Drawings, to be cut with rapidity, economy,
and perfection. In such dies and taps, the portion of the thread extending
backwards from each cutting edge a towards the next succeeding cutting
edge is eccentric to the axial line of the tap or die, and the mechanism
herein-after described cuts such eccentric threads by means of a rotating
cutter which while revolving is caused to approach and.recede from the
axial line of the blank as many times as there are cutting edges to be
made while the blank is turned upon its axis and fed longitudinally past
the position of the rotating cutter. The blank so eccentrically cut is
subsequently fluted longitudinally by a milling or planing machine
so as to produce cutting edges at the most protuberant parts of the
threads.
The said improvements comprise various new combinations of instru-
mentalities, the first of which consists of the combination of a rotating
mandril to hold and turn the blank, a vibrating rotating cutter to cut
the groove between the threads, a cutter arbor inclined to the axis of
the rotating mandril (for the purpose of enabling the cutter to cut an
inclined thread), a feed screw or equivalent mechanism to determine
the pitch of the thread cut, and a regulating cam for varying the position
of the rotating cutter during the revolution of the mandril so as to
impart the required eccentricity to the thread.
The special object of the second improvement in machinery is to
guide the portion of the cutter that is operating upon the blank so that
it may run truly notwithstanding the warped condition of the cutter
produced by tempering or other causes. This improvement consists of
the combination of the rotating mandril for the blank with a rotating
cutter mounted upon an arbor that is free to play endwise in its boxes

page_text: with a guide for the side of the cutter to run against, and with a spring.
(or its equivalent operating with a yielding pressure) to keep the cutter
constantly in contact with the guide, so that the guide determines the
position of the acting portion of the cutter in its immediate vicinity.
The special object of the third improvement in machinery is to enable
the inclination of the cutter arbor to the axial line of the rotating
mandril and blank to be readily varied to adapt the machine to cutting
threads of different inclinations. This improvement consists of the
combination of the rotating mandril (for turning the blank) with the
arbor of the cutter by means of a vibrating support for said arbor (or
vibrating tool support, as it will herein-after be called), and a moveable
centre block or its equivalent for changing the position of one or both of
the centres upon which the tool support vibrates, so that the inclination
of the cutter arbor may be varied by varying the position of said centre
block or its equivalent..
The special object of the fourth improvement in machinery is to cause
tlie cutter to vibrate in accordance with the form of the regulating cam,
and also to prevent it from running into the metal too deeply. This
improvement consists of the combination of the rotating mandril and
rotating cutter with a cutter arbor inclined to the axial line of the
mandril, a regulating cam to determine the eccentricity of the cut made,
and a weight (or its equivalent) operating antagonistically to the cam
to exercise a yielding pressure which causes the cutter arbor to vibrate
in accordance with the form of the regulating cam, and at the same time
prevents the cutter from running into the work.
The special object of the fifth improvement in machinery is to enable
the rotating cutter to be readily set to its proper position, .or. at the
required distance from the axial line of the mandril and blank, so that
taps of different sizes may be cut, and that cutters of different diameters
may be used without changing. the. regulating, cam.. This improvement
consists of the combination of the rotating cutter. and the regulating
cam (that regulates its position) by means of connecting mechanism
whose length is adjustable by means of a screw or its equivalent for
that purpose, so that the position of the rotating cutter relatively to the
regulating cam may be varied as required.
..
The special object of the sixth improvement in machinery is to cause
the rotating cutter to cut progressively nearer to the axial line of the
blank as the blank is moved longitudinally past it, so as to cut the

page_text: threads of tapering taps or dies.
This improvement consists of the
combination of the regulating cam and the vibrating tool support with
a variable connecting or combining mechanism interposed between the
two, and a directing instrument for varying the effective length of said
connecting mechanism as required to cause the same protuberance of the
regulating cam to move the cutter to different extents; hence as the
cutting proceeds the cutter is not moved as near to the axial line of
the mandril and blank during one revolution of the regulating cam as
during the preceding revolution, so that the thread cut is tapering
although the protuberances of the cam do not vary.
The machine represented in the accompanying Drawings embodies all
the said improvements in machinery in the best form thus far
devised, and is represented as arranged for cutting excentric taps;
it has a bed or shears A supported on legs, and of the same general
construction as the shears of engine lathes, its top being provided with
guides or ways b, b', upon which the carriage C which supports the tap
blank is arranged to slide longitudinally. The bed also is provided at
one end with a fixed head d, which supports the cog wheels that
transmit motion to the moving members of the machine.
The carriage
has at one end a mandril B that is constructed to turn in suitable
boxes f, f, that project above the bed of the carriage, and this mandril is
provided at its inner end with a clamp chuck g, by which the head of
the tap blank D is secured to the mandril so as to be turned by it. The
end of the carriage opposite the mandril is fitted with a moveable head h
that supports the dead centre c upon which the small end of the tap
blank turns during cutting. The base of this moveable head is provided
with a longitudinal projection or feather, which slides in a groove formed
in the bed of the carriage, so that the head is maintained in a central
position on the carriage, although it may be moved towards and from
the mandril. The head his clamped to the carriage by means of a
screw bolt. The bottom of the sliding head is inclined, and a wedge of
the same inclination is inserted beneath the base upon the upper surface
of the bed of the carriage, so that the head may be adjusted by
inserting the wedge more or less to raise or lower the dead centre,
as may be required in setting the tap blank in the machine. The
tap carriage C is moved to and fro by means of a feed screw E,
which is arranged to turn in bearings at one side of the bed of the
machine, and which is connected with the tap carriage by means of a

page_text: sectional nut F that is secured to the carriage, so that the carriage is
screwed along by the turning of the feed screw. One end of the shaft
of the feed screw. E projects beyond its bearing at the end of the
machine, and is fitted with a cog wheel G, by which the feed screw
is turned for the purpose of moving the tap carriage. In order that the
tap blank may be turned upon its axis during cutting the mandril B is
fitted with a cog wheel H, whose teeth engage with those of a pinion H'
that is secured to a sleeve n, which turns in bearings f¹, f', upon the
tap carriage. The bore of the pinion sleeve n is traversed by a square
shaft J, which extends to one end of the bed of the machine, where it
passes through a bearing. The end of the shaft J projects through this
bearing, and is fitted with a cog wheel G', by turning which the shaft J,
the sleeve n, the pinion H', and the mandril B, with the tap blank, are
all turned. The pinion sleeve n is arranged to slide longitudinally in
its bearings, so that the pinion may be disengaged from the cog wheel H
to permit the mandril to be turned by hand during the operation of
securing the tap blank and removing it. When the pinion is engaged
with the wheel it is held in place by a latch I' which intervenes between
a shoulder upon the pinion sleeve and the side of the adjacent bearing f¹,
The rotary
and prevents the longitudinal movement of the sleeve.
cutter I by which the screw thread of the tap is cut consists of a disk
of steel whose periphery is turned to the form of the groove between the
threads to be cut, and is then cut into teeth like those of the rotary
cutters of milling machines for cutting metals, after which it is
hardened and tempered; it is mounted upon an arbor K, which is
supported by the bearings p, p, of a tool support L, which is arranged
to vibrate upon two centres s, s, so that the rotary cutter may move
towards or from the axis of the mandril and tap blank for the purpose
of cutting the thread eccentric. In order that the cutting edge of the
cutter may be maintained in its proper position notwithstanding
irregularities in the cutter the arbor K is constructed to slide longi-
tudinally in its bearings, a spring M is provided to act upon the end
that is furthest from the cutter, and a fixed guide N is applied to the
outer face of the disc of the cutter as closely as possible to the cutting
edge; hence the pressure of the spring causes the face of the rotary
cutter to run constantly in contact with the guide, and permits the arbor
to move so as to adapt itself to the irregularities which are generally
found in such tools, while the part of the cutting edge which is acting,
being directed by the guidé, runs truly or thereabouts.

page_text: In order to cut the screw thread on the tap blank with the inclination
corresponding with the pitch of the thread the cutter arbor K is inclined
to the axial line of the mandril and tap blank.. And in order that the
same machine may be used for cutting taps of different pitches and
diameters the block O to which the tool support is pivotted by the
centres s, s, is secured to a bracket projecting from the bed of the
machine by means of screws t, t, which pass through inclined slots in
the centre block O, so that the centre block may be adjusted upon the
bed of the machine to hold the tool support in different positions as
required to vary the inclination of the cutter arbor to the axial line of
the tap blank. The cutter arbor is fitted with a belt pulley Q, to which
the driving belt is applied, and motion is communicated from this arbor
to the feed screw E and to the shaft J that turns the mandril B by
means of two pulleys R, R', a belt S, and a train of cog wheels
G, G¹, G³, G³, Gʻ, G³, G, G'. One of the pulleys R which the belt S
encircles is secured to the cutter arbor K; the other pulley R¹ which
the belts encircles is secured to a sleeve which turns freely upon a stud
projecting from an arm T, which swings upon the outer end of a stud q
that is fixed to and projects from the head d of the bed of the machine.
The pulley sleeve is fitted with the cog wheel G³, whose teeth engage
with those of a cog wheel G³, which is secured to a sleeve that turns
upon the same fixed stud q that the arm T swings upon; hence the two
cog wheels G³, G³, are always properly engaged however the pulley R'
may rise or fall to accommodate itself to the rising or falling of the
cutter arbor K, to which the first pulley R is applied. In order that
the belt S may be properly strained to prevent it from slipping on the
pulleys the swinging arm T has a weight U applied to its end. The
sleeve of the cog wheel G³ carries a second cog wheel G, which gears
into the cog wheel G¹ that is secured to the shaft J that transmits motion
to the mandril B: this shaft also is fitted with a second cog wheel G³,
which imparts motion to the feed screw E through the intervention of
the cog wheel G fixed to it and an intermediate cog wheel G, that
turns upon a stud secured to the frame of the machine.
In order that the cutter may be raised and lowered to cut eccentric
threads of the required form upon the tap blank a cam V is provided,
having as many projections as there are to be cutting edges upon the
periphery of the finished tap. This regulating cam is mounted upon
a shaft W that turns in bearings upon the frame of the machine, and

page_text: is fitted at one end with a cog wheel G that gears into the cog
wheel that is secured to the shaft J which transmits motion to the
mandril B, so that the cam is turned with the mandril. The relative
proportions of the two cog wheels G³, G, intervening between the
shaft J and the regulating cam V are the same as those of the two
cog wheels H', H, that intervene between the same shaft J and the
mandril B, so that the tap blank (which is held by the mandril) and
the regulating cam turn with the same speed. The regulating cam is
caused to regulate the position of the rotating cutter, in the following
manner: A strong frame consisting of the standard X and the two
arched bars r, r, is erected upon the frame of the machine, and a
lever Y is pivotted to this frame by a pivot u in the vicinity of the
standard X. The outer end of this lever is connected by an adjustable
connecting rod Z with a second lever Y¹, whose inner end is formed
into a head that bears against the under side of the regulating
cam V, so that this bearing lever Y' and the first or upper lever Y
are caused to vibrate as the regulating cam revolves. The upper lever
is connected with the vibrating tool support L by a stud z, upon the
upper end of which the said upper lever bears, so that whenever a
projection of the regulating cam V depresses the bearing lever Y¹ and
the upper lever Y the rotating cutter is forced nearer to the axial line
of the mandril and the tap blank, and whenever the form of the
regulating cam permits the bearing lever Y₁ and the upper lever to
rise the rotating cutter is permitted to rise or move further from the
axial line of the mandril and tap blank. In order that the rotating
cutter may be moved from the axial line of the mandril and tap blank
with certainty, so as to cut a thread corresponding with the eccentricity
of the projections of the regulating cam the vibrating tool support is
provided with a weighted lever A', which bears upon a stud z¹ that is
placed between the weight U and the pivot u that secures the lever
to the tool support, and whose lower end is sustained by the bed. of
he machine, so that the weight U', acting upon the vibrating tool
support antagonistically to the regulating cam, tends to move the tool
support and the rotating cutter away from the axial line of the mandril
and tap blank, and causes the bearing lever Y¹ to bear constantly against
he regulating cam V, and to apply itself to the surfaces of its pro-
ections. The rotating cutter is thus acted upon by two forces, the
one applied by the weight, and being a yielding pressure that tends to
nove the cutter from the axial line of the mandril and tap blank,

page_text: and the other being the positive force applied by the regulating cam V,
that preponderating over the said yielding pressure forces the cutter
towards the axial line of the mandril and tap blank, and as the bearing
lever Y is constantly borne against the regulating cam the form of
the cut produced by the rotating cutter is regulated by the form of the
cam projections. The weight U is made sufficient to overcome the
tendency of the rotating cutter to run into the work, and thus act more
deeply than it should, hence the weight U' controls the cutter, and
the lever A¹ on which the said weight acts may be called the controlling
lever. In order that the same cam may be used to regulate the cutting
of the threads of taps of different diameters, and may also be used to
cut taps of the same size with cutters of different diameters, the
mechanism that combines the rotating cutter with the regulating cam
is made adjustable in the following manner-The connecting rod z
between the bearing lever Y' and the upper lever Y is fitted with a
screw d', which passes through a nut formed in the upper end of the
connecting rod, and bears upon the upper lever Y, hence by turning
this screw the effective length of the connecting rod, or the distance
between the upper lever Y and bearing lever Y¹ can be adjusted as
required to set the cutting edge of the cutter at the proper distance
from the axial line of the mandril and tap blank, and thus regulate
the depth of cut. The fulcrum stud z¹ of the controlling lever A' is
also made adjustable by applying its lower end to a screw which
turns in a base g2, whose lower end is grooved to rest upon the tap
carriage C. This screw head is provided with a capstan bar e, by
turning which the fulcrum stud z¹ is raised or depressed as required.
If the machine thus described be set to work upon a tap blank the
latter will be turned by the mandril B, the pitch of the thread will be
determined by the feed screw E, the form of the thread by the profile
of the periphery of the rotating cutter V, and the inclination of the
cutter arbor K, and the number of the cutting edges and the eccentricity
of the threads by the number and form of the projections of the regu-
lating cam V. If the machine be thus used without any change in the
adjustment of the parts the tap blank cut will be of the same section
throughout its length, or will be suitable for a plug tap without taper.
In order to adapt the machine to cutting blanks for taper taps the
mechanism for regulating the position of the rotating cutter is made
self-adjusting, so as to cause the rotating cutter to recede from the axial

page_text: The form
line of the mandril and tap blank as the blank is moved point foremost,
and longitudinally past the cutter. To this end the mechanism that
combines the rotating cutter with the regulating cam is made variable
by pivotting the bearing lever Y' to an elbow lever Y, which is con-
structed to swing upon a stud q secured to the bed of the machine, so
as to raise and lower the fulcrum of the bearing lever Y', the pivot that
connects it with adjustable connecting rod Z and the upper lever Y. The
upper end of the elbow lever is provided with a cord ha, whose end is
wound upon the extremity of the shaft W of the regulating cam V.
Hence as the cam is turned the cord he is unwound from its shaft and
the elbow lever Ys is moved to relax the pressure upon the bearing
lever Y', thereby permitting the rotating cutter to recede more and
more (as the cutting proceeds) from the axial line of the mandril and
tap blank and to impart the required taper to the tap blank.
of the taper thus imparted may be varied by varying the diameter and
form of the extremity of the cam shaft W, which directs the amount
of variation (by determining the movement of the elbow lever Y through
the cord) and is therefore the directing instrument in the machine, and
the taper may be caused to increase progressively (so as to impart a
curved profile to the tap) by making the end of the cam shaft on which
the cord is wound of progressively greater diameter, thus giving it a
conical or conoidal form. As the same machine may be used for cutting
plug taps or taps partly cylindrical and partly tapering a stop is
provided to hold the elbow lever Y* (and consequently the fulcrum pin
of the bearing lever Y¹) in a fixed position when the directing instru-
ment is not varying it. When the machine is used for cutting taps the
cutting proceeds from the point to the head of the tap. When the tap
is thus cut it is taken from the machine and put into a milling machine,
by which it is fluted longitudinally so as to produce the cutting edges
at the most protuberant parts of the tap blank.
The combinations of mechanism existing in the machine thus described
may be applied to the cutting of the dies for cutting the threads of screw
bolts and similar articles. In such case the mandril is provided with
a chuck of suitable form and size to hold the die blank to be cut, and
the die blank previously bored to. the approximate size of the interior
of the thread is applied to the chuck. The rotating cutter used must
be sufficiently small to enter into the bore of the die and vibrate therein,
so as to cut the thread, and if a guide be used it should be placed on

page_text: the inner side of the cutter (that is, on the side towards the driving
pulley Q), the spring being forked and arranged to bear against a collar
on the arbor, so as to draw said arbor towards the spring (instead of
pushing it), and thereby keep the inner face of the cutter running
against the guide. For the purpose of getting rid of the cuttings the
parts of the machine may be so arranged that the rotating cutter is
borne upwards by the action of the regulating cam against the upper
side of the interior of the die; and for the same reason the machine for
cutting taps may be arranged to bear the rotating cutter upwards against
the under side of the tap blank instead of downwards upon its upper
side. The cutter described and represented in the Drawings is adapted
to the cutting taps with V threads, but threads of other forms may be cut
in the same machine by varying the profile of the cutter. The pitch of
the thread may be varied by changing the feed screw or by varying the
proportions of the wheels that impart motion to it in the manner
usual in screw-cutting lathes, and the inclination of the arbor of the
cutter 'to the axial line of the mandril should always be such as to make
the inclination of the plane of the cutter substantially the same as that
of the thread of the screw.
When tap and die blanks which are partly cylindrical and partly tapering
are to be cut the axial line of the two centres (s, s,) of the vibrating
tool support should be parallel to the axial line of the mandril B. In
such cases the distances between the cutter arbor and the axial line
of the centres must be less at one end than at the other in order that
the cutter arbor may be properly inclined to the axial line of the
mandrel and blank. As machines may be built in this manner for
cutting blanks having threads of different inclinations, the variation in
the inclination of the cutter arbor may be obtained by fitting one or
both of the centres s, s, to moveable centre blocks that are secured by
screw bolts to
to the tool support, so that the parallelism of the axial line
of the centres and mandrel may remain unchanged, while the distance
between the cutter arbor and the one or both centres may be varied (by
moving one or both centre blocks) to vary the inclination of the cutter
arbor to the mandril. In the machine thus described a regulating cam
having as many protuberances as there are to be cutting edges in the
tap is employed, but a regulating cam having a different number of
protuberances, may be used if the speed of the cam shaft W be corre-
spondingly varied. Thus, for example, if there are to be four cutting

page_text: edges on the tap a regulating cam with a single snail-formed protu-
berance may be used if the wheels for imparting motion to its shaft be
so proportioned as to cause the cam to turn four times for teach revolution
of the mandril that carries the blank. Thus far the blank has been
described as being moved longitudinally past the rotating cutter, that
being the arrangement which is preferred, but the mandril bearings
may be fixed to the bed of the machine, and the cutter and its arbor
may be mounted on a carriage and moved along the bed if deemed
expedient.
Having thus described a machine embodying all the improvements,
I declare that I do not claim the Invention of any number thereof
separately, but what I claim as the Invention and desire, to secure by
Letters Patent is,-
The eccentric die, constructed substantially as before described, with
its threads eccentric to the axis of the die and with the cutting edges
nearest to the said axis...
Also the combination in one machine of the following instrumen-
talities, viz., the rotating mandril to support the blank, vibrating rotating
cutter, inclined cutter arbor, feed screw, and regulating cam, all formed
and constructed to adapt them to the purpose to be accomplished,
and all combined and operating in the machine, substantially as before
set forth.
Also the combination in a machine of the following instrumentalities,
viz., the rotating mandril, rotating cutter mounted on a free arbor,
cutter guide, and spring, all formed and constructed to adapt them
to the purpose to be accomplished, and all combined and operating in
the machine, substantially as before set forth.
Also the combination in a machine of the following instrumentalities,
viz., the rotating mandril, cutter arbor, vibrating tool support, and
moveable centre block, all formed and constructed to adapt them to the
purpose to be accomplished, and all combined and operating in the
machine, substantially as before set forth.
Also the combination in a machine of the following instrumentalities,
viz., the rotating mandril, rotating cutter, inclined cutter arbor, regu-
lating cam, and weight, all formed and constructed to adapt them to the
purposes to be accomplished, and all combined and operating in the
machine, substantially as before set forth.

page_text: Also the combination in a machine of the following instrumentalities,
viz., the rotating cutter, regulating cam, and adjustable connecting
mechanism, all formed and constructed to adapt them to the purpose to
be accomplished, and all combined and operating in the machine,
substantially as before set forth.
Also the combination in a machine of the following instrumentalities,
viz., the regulating cam, vibrating tool support, variable connecting
mechanism, and a directing instrument, all formed and constructed to
adapt them to the purpose to be accomplished, and all combined and
operating in the machine, substantially as before set forth.
In witness whereof, I, the said George Tomlinson Bousfield,
have hereunto set my hand and seal, this Sixth day of October,
in the year of our Lord One thousand eight hundred and sixty-
eight.