IMPROVEMENTS IN CUTTING SCREW TAPS AND DIES, AND IN APPARATUS APPLICABLE TO LATHES FOR THAT PURPOSE
Year: 1875

page_text: LETTERS PATENT to John Imray, of No. 20, Southampton Buildings,
Chancery Lanc, in the County of Middlesex, for the Invention of
"IMPROVEMENTS IN CUTTING SCREW TAPS AND DIES, AND IN APPARATUS
APPLICABLE TO LATHES FOR THAT PURPOSE."-A communication from
abroad by Henry E. Boyd, of Pittsburg, Pennsylvania, in the United
States of America.
Sealed the 21st September 1875, and dated the 3rd August 1875.
PROVISIONAL SPECIFICATION left by the said John Imray at the
Office of the Commissioners of Patents, with his Petition, on the
3rd August 1875.
I, JOHN IMRAY, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN CUTTING SCREW TAPS AND DIES, AND IN
APPARATUS APPLICABLE TO LATHES FOR THAT PURPOSE," to be as follows:-
According to this Invention screw taps and dies, instead of having
their screw threads first cut, and being thereafter grooved in the usual
manner, whereby a burr is raised, are first grooved, and have their

page_text: threads cut afterwards, with a deepening of the threads to give clearance
or reliéf behind the cutting edges, such thread cutting being effected by
apparatus that can be readily applied to an ordinary screw-cutting lathe.
For this purpose the ordinary feed shaft of the lathe is made to work
the chuck and mandril by worm gearing, and is provided with loose,
slow, and quick pullies, which are severally clutched by the action of
cams placed on the lathe chuck, so that the latter has a slow motion
during each cut and a quick motion to avoid loss of time between the
cuts, that is to say, when the cutter is passing over the grooves of the
blank operated on other cams on the chuck acting on a rocking shaft
cause a revolving cutter to approach towards and recede from the lathe
centre, thereby varying the depth of cut as required to give clearance or
relief.
The chuck or lathe mandril instead of being driven from the feed
shaft as above stated may be driven from a separate countershaft pro-
vided with stepped pullies and gearing, and with a sliding clutch worked
by cams on the chuck so as to increase the speed between the cuts and
retard it during the cuts.
For cutting dies for bolts or pipes the chuck is provided with a ring
or holder to secure the die blank, and has cams upon it for varying the
speed and depth of cut, as already described.
The cutting of the threads is effected by a rotary cutter mounted on
the slide rest, the longitudinal movement of which is effected by the feed
screw in the usual way, while the lateral movement is, as mentioned
above, controlled by cams on the chuck so as to vary the depth to
which the cutter is made to enter the blank or piece operated on.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Imray in the Great Seal Patent Office
on the 23rd November 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
IMRAY, of No. 20, Southampton Buildings, Chancery Lane, in the
County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Third day of August, in the year of our

page_text: Lord One thousand eight hundred and seventy-five, in the thirty-ninth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said John Imray, Her special license that I,
the said John Imray, my executors, administrators, and assigns,
or such others as I, the said John Imray, my executors, admini-
strators, 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 CUTTING
SCREW TAPS AND DIES, AND IN APPARATUS APPLICABLE TO LATHES FOR THAT
PURPOSE," a communication to me from abroad by Henry E. Boyd, of
Pittsburg, Pennsylvania, in the United States of America, upon the
condition (amongst others) that I, the said John Imray, 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 Imray, 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
Sheet of Drawings, and to the figures and letters marked thereon, that is
to say :-
According to this Invention screw taps and dies instead of having
their screw threads first cut, and being thereafter grooved in the usual
manner, whereby a burr is raised, are first grooved, and have their
threads cut afterwards, with a deepening of the threads to give clearance
or relief behind the cutting edges, such thread cutting being effected by
apparatus that can be readily applied to an ordinary screw-cutting lathe.
For this purpose the ordinary feed shaft of the lathe is made to work
the chuck and mandril by worm gearing, and is provided with loose,
slow, and quick pullies, which are severally clutched by the action of
cams placed on the lathe chuck, so that the latter has a slow motion
during each cut, and a quick motion to avoid loss of time between the
cuts, that is to say, when the cutter is passing over the grooves of the

page_text: blank operated on other cams on the chuck acting on a rocking shaft
cause a revolving cutter to approach towards and to recede from the lathe
centre, thereby varying the depth of cut as required to give clearance or
relief.
The chuck or lathe mandril, instead of being driven from the feed
shaft, as above stated, may be driven from a separate countershaft pro-
vided with stepped pullies and gearing, and with a sliding clutch worked
by cams on the chuck so as to increase the speed between the cuts and
retard it during the cuts.
For cutting dies for bolts or pipes the chuck is provided with a ring 1
or holder to secure the die blank, and has cams upon it for varying the
speed and depth of cut, as already described.
The cutting of the threads is effected by a rotary cutter mounted on
the slide rest, the longitudinal movement of which is effected by the
feed screw in the usual way, while the lateral movement is, as ]
mentioned above, controlled by cams on the chuck so as to vary
the depth to which the cutter is made to enter the blank or piece
operated on.
part of an ordinary screw-cutting lathe, to which is applied apparatus
for cutting tap or die threads according to this Invention.
Fig. 4 is a plan and Fig. 6 a side view of a lathe shewing a modified
arrangement of the driving gear.
Fig. 5 is a perspective view shewing the holder for a die.
Fig. 7 is a longitudinal section to an enlarged scale of the driving
spindle with means of varying the speed.
Fig. 8 is a side view of a tap, and Fig. 9 is a front view of a die such
as operated on by the mechanism which will now be described.
2
Referring to Figs. 1, 2, and 3, A is the frame of the ordinary lathe; 3
B is the headstock, with the ordinary pulleys and other appliances, and
connected by a series of change wheels b with the feed screw C in the
usual manner. E is the poppet head, and D the tool rest. So far the
lathe is of ordinary construction. The contrivances applied to it for

page_text: the manufacture of screw taps are of the following description:-On F
the ordinary feed shaft, attached to the side of the frame by brackets f,
are placed loose pulleys G, G'; G being the smaller or speed pulley, and
G¹ the larger or slow pulley, the latter being stepped at g, g', g², so as to
give several rates of speed to suit different sizes of taps, this latter pulley
being used to drive the shaft when the cut is made. Between the quick
and slow pulleys G, G¹, is a sliding clutch H worked by a lover I, which
is mounted on a bracket attached to the main frame and worked by the
rod J, which slides in brackets attached to the upper portion of the
frame or to the headstock. Upon the end of the sliding rod J next the
tool rest is a projection or arm j, which is made to bear against the face
of the worm wheel K by a spiral spring at the end of the rod next I.
K is a worm wheel on the mandril, having a centre for the blank from
which the tap is to be cut. The feed rod F, by bevil gearing f³, works
the worm L, which gives motion to the worm wheel K. On the feed
rod F a swinging joint F¹ may be fitted, whereby the worm L can be
swung back out of gear with the worm wheel on taking out screws F
or undoing any other suitable fastening, thus rendering the lathe
available for ordinary turning. M indicates the blank supported between
the centres, and engaged with the worm wheel K by the usual carrier m.
Upon the face of the worm wheel K, at intervals corresponding with the
number of grooves in the tap, are cams or inclines k, k¹, of which there
are two at each point, the one k abrupt for working the clutch H, and
the other more gradual for operating an elbow lever N, which is
pivoted to an arm projecting from one of the bearings of a shaft P.
One end of the elbow lever N bears against the face of the worm
wheel K, and the other end works an arm or projection p, giving
rocking movement to the shaft P, which is mounted in bearings O, O,
on the main frame parallel to the travel of the tool rest. Part of the
shaft P is made eccentric, so that when the shaft is rocked a rod Q
extending from it to the tool rest causes the latter to move forward,
bringing a revolving cutter against the blank at the regular intervals
when the elbow lever N passes over the cams upon K. R is a spring
attached at one end to an arm on the rocking shaft P, and at the other
end to a fixed point upon the frame or bearing, so as to retract the
shaft when the end of the elbow lever N passes off the cam.
S is a
revolving cutter mounted on the tool rest and driven by a pulley S'.
The cutter S has an edge V shaped, or of other form suited to the screw
thread.

page_text: The arrangements above described can be readily attached to or
detached from the ordinary lathe. Instead of these the arrangements
shewn in Figs. 4 to 7 may be used, these being so compact in their
character that they may remain permanently attached to the lathe
without being in the way.
Referring to Figs. 4, 5, 6, and 7, A is the frame; B, the headstock,
with its pulleys '; and C, the feed screw, which is moved by the change
wheels b. D is the tool rest moved by the feed screw C, and having on
it the revolving cutter S, provided with its driving pulley S¹. The
transverse slide of the rest is connected by a link d to an eccentric
rocking shaft P¹, pivotted at one end in a slide e on the poppet head E,
and at the other provided with a universal joint or hinge connection e¹,
and journalled near the headstock B. Attached to the end of the
shaft P¹ next the face plate is an arm which stands in the path of a
cam k upon the face plate, so that at intervals the shaft P¹ is slightly
rocked on its axis, and thus draws forward the cutter at the time the
blank is being cut, so as to give the "clearance" or "relief" required
in the thread of the tap or die. K is the face plate toothed to form a
worm wheel, which gears with the worm L. To the face of K (Fig. 5)
is secured a ring K¹ provided with set screws 1, forming a chuck to hold
a pipe or bolt die while the internal thread is cut. This ring K¹ may be
removed when not required. M is a tap blank supported between the
centres, and driven from the face plate K by the usual carrier m. Upon
the back of the face plate K, or that side next to the driving pulleys, at
regular intervals corresponding to the cuts to be made on the blank, are
a series of cams or inclines k, which actuate the clutch lever of the
driving gear and also the eccentric shaft P¹, which brings the cutter up
to its work. I is the clutch lever mounted between the back of the face
plate and the brackets of the headstock. It is pivoted, as at i³, to the
frame A or to the headstock, and is pushed by a spring so that a pro-
jection on it c bears against the back of the face plate, and at regular
intervals engages with the cams k, which pushing back the lever moves
the clutch on the driving shaft at the same time that the face of the
cam actuates the lever I the side of the cam engages with the arm of
the eccentric shaft P¹, causing the shaft to rock slightly, so as to push
in the tool holder and bring the cutter into action. Thus the cams on
the face plate serve to actuate simultaneously the speed changing and
the cutting mechanism. L is a vertical worm stepped in a bracket

page_text: secured to the frame A and gearing with the teeth of the face plate, and
driven by bevil wheels f³ from a driving shaft M', which is worked from
the pulleys of the headstock. As the speed with which the blank
rotates is varied at regular intervals this shaft and its pulleys are for
that purpose constructed as shewn in Fig. 7. The shaft M' is bored
out for about two-thirds of its length for the reception of a tapered
spindle N¹, and is slotted to receive a set of friction blocks n.
The hinder part of the shaft is enclosed within the speed pulley G,
which holds the blocks n in the slots. The spindle N¹ is secured to
the sliding clutch H by a pin h, which passes through a slot in the
shaft M', so that the spindle N' moves longitudinally with the sliding
clutch, both the clutch and the spindle rotating with the shaft M'. The
speed pulley G revolves loosely when not clutched to the shaft by the
friction blocks 1. G¹ is a gear wheel by which the slow motion is
imparted to the shaft; it is like the speed pulley G loose upon the
shaft M', but the boss of G' is provided with a set of spring dogs o,
which take into notches in the shaft M', permitting the gear wheel to
slip on the shaft when the shaft is driven by the speed pulley, but
causing the wheel to clutch the shaft when it drives it for the slow
motion, the speed pulleys then running loose upon the shaft.
The shaft M' is mounted in brackets B' attached to the frame A or to
the headstock, and the speed pulleys are driven by belting from the
pulleys of the headstock, but the slow motion is obtained through gear
wheels 1', 21, (Fig. 5) on a shaft R' mounted in the same bracket as M'.
The pinion can slide upon the shaft R', being held by a feather or
other suitable means, and thus by simply sliding the pinion » out of gear
with G', and unshipping the belts from the speed pulleys, the headstock
is readily freed from the remaining driving gear, and the lathe can be
used in the usual manner without the removal of any other parts.
"
Usually in cutting a screw tap a plain blank is employed, and the
thread is cut thereon by a tool having a forward motion, increasing at
certain regular intervals so as to cut deeper and give what is termed a
"clearance" or
relief," these clearances or reliefs corresponding to the
grooves or flutes that are afterwards to be formed upon the tap. In thus
forming the tap by first cutting the thread and then grooving, the thread
is injured or burrs are formed, which necessitates the filing of the teeth
or cutting portions to remove the burrs, and so increases the cost of
manufacture.

page_text: To avoid these objections the blanks are, according to this invention,
first fluted or grooved, then placed, as shewn at M, Fig. 1, so that the
grooves correspond to the intervals between the cams on the face of the
worm wheel, and the portions to be cut correspond to the cams. Power
is now applied through the speed pulley to the feed shaft F, and com-
municated through the bevil and worm gearing to the worm wheel; it
is made to revolve rapidly while the intervals between the cams are
passing, then the projection ; being struck by the abrupt or outer cam k
causes the sliding rod J to move the sliding clutch on the shaft F, so
causing it to engage with the pulley G', which drives the feed shaft F
at less speed while the cut is being made upon the blank. At the same
time the end of the lever N bearing on the inclined cam causes the
shaft P to rock, and this by means of the rod O advances the tool holder
so as to bring the rotary cutter S into position to cut the thread, the
incline of the cam being so graduated as to cause a progressive forward
movement of the tool holder, and thus to give the deepest cut or relief
just as the groove is reached, where the clearance or relief is required.
The projections upon the rod J and the elbow lever N simultaneously
leave the cams, whereupon the spring upon J moves back the clutch
lever, engaging the clutch with the swift pulley G, so that the worm
wheel and blank are made to revolve faster between the cuts, and loss
of time is thus avoided.
When the modified form of gearing shewn in Figs. 4 to 7 is employed,
the power is applied through the speed pulley G to the shaft M', and
thence through the worm L to the face plate K, which is made to
revolve rapidly until the cam & coming in contact with the projection
on the clutch lever I slides the clutch H so as to engage with the gear
wheel G', the clutch at the same time moving the taper spindle N¹
longitudinally backwards, so that its cone frees the friction blocks n, and
permits the speed pulley G to revolve loosely. The shaft M¹ being in
that case driven only by the slow pulley, the speed of the face plate is
decreased during the cutting. At the same time that the face of the
cam k moves the clutch lever I its side actuates the arm on the shaft P',
causing it slightly to rock so as to bring forward the tool holder and
cutter S. As soon as the cam k passes the arm of P¹ and the projection
on the lever I, the shaft and lever are brought back to their first position
by springs. The clutch H is thus disengaged from the slow wheel, and
draws forward the taper spindle N¹ (which motion is assisted by a

page_text: spring n acting on the end of the spindle), so that its cone forces out
the friction blocks n and thus engages the shaft M¹ with the speed
pulley, causing the face plate to revolve rapidly until another cam k
comes into action. The reverse movement of the shaft P has in the
meanwhile withdrawn the cutter S. These several operations of the
machine are repeated until the "tap" is fully cut, the slide rest being
moved along the lathe bed by the feed screw in the usual manner.
When a pipe or bolt die is to be cut the ring K' is secured to the face
plate and the die (Fig. 9) is secured within the ring or holder by means
of the thumb or set screws 1, care being taken that the bits or cutting
portions are set to correspond with the cams on the face plate; the
cutter mounted on a shaft of sufficient length to reach through the die
is then brought forward and adjusted within the die, and power being
applied the apparatus operates as already described for the cutting of a
tap."
"
When it is desired to use the lathe simply for turning if it is supplied
with gear shewn in Figs. 1, 2, and 3, the worm L can be swung back
out of gear with the face plate, so that the lathe can be worked by its
ordinary pullies. The cutter also being removed leaves the lathe
comparatively free as the bell-crank lever N is not in such a position as
to interfere with the ordinary use of the lathe. The bearings of the
rocking shaft P which also carry the elbow lever may be made so as to
be readily detachable, either by dovetailed guides or in any other suitable
manner.
From the above description it will be seen that the apparatus has the
advantage of being very simple, and of being easily attached to or
removed from the ordinary lathe, whilst the requisites for cutting taps
are fully attained by its use, namely, the alternately fast and slow
motion of the blank, whereby the cutting tools are not injured nor time
lost between the cuts, and the automatic progressive forward movement
of the cutter so as to give the required clearance or relief.
The method adopted of first grooving or fluting the blank avoids the
expense heretofore incurred by the subsequent filing to clear the teeth
from the burr invariably formed by grooving or fluting after the threads
have been cut.
Having thus described the nature of this Invention and in what

page_text: manner the same is to be performed, as communicated to me by my
foreign correspondent, I claim,―
First. The method of cutting screw taps by first fluting or grooving
the blank, and then cutting the thread thereon, substantially as and for
the purposes herein set forth.
Second. The use for cutting the threads of screw taps of a revolving
cutter having an edge shaped to a V or other form corresponding to that
of the thread.
Third. The use in cutting the thread of screw taps or dies of cams
upon the chuck of a lathe acting on clutch gear, whereby the speed of 1
revolution is rendered slow during the cut and quick during the passage
of the grooves or those parts of the blank which are not cut, thereby
avoiding loss of time, substantially as herein described.
Fourth. The use in cutting the thread of screw taps or dies of cams
on the chuck acting on the tool holder so as gradually to deepen the cut 1
towards the grooves, thereby giving the clearance or relief, substantially
as herein described.
Fifth. The mechanism applicable to a screw cutting lathe for the
purpose of varying the speed while cutting the thread of screw taps or
dies, such mechanism being a combination of the cams / on the chuck K, 2
the spring rod J, lever I, clutch H, quick and slow pullies G and G¹ on
the feed shaft F, bevil gearing f³, and worm L engaging with the teeth
of the chuck K, substantially as herein described with reference to
Figs. 1, 2, and 3 of the accompanying Drawings.
Sixth. The mechanism applicable to a screw cutting lathe for the 2
purpose of varying the depth of cut while cutting the thread of screw
taps or dies, such mechanism being a combination of the cams k¹ on the
chuck K, the bell-crank lever N, eccentric rocking shaft P, and rod Q,
connected to the sliding tool holder, substantially as herein described
in reference to Figs. 1, 2, and 3 of the accompanying Drawings.
3
Seventh. The mechanism applicable to a screw cutting lathe for the
purpose of varying the speed while cutting the thread of screw taps or
dies, such mechanism being a combination of the cams / on the back of
the chuck K, the clutch lever I, clutch H, driving shaft M' with internal
coned spindle N¹, external speed pullies G, sliding dogs n, slow wheel G, 3
and spring catches o, bevil gear and worm L gearing with teeth of
E

page_text: chuck K, substantially as herein described with reference to Figs. 4, 5,
6, and 7 of the accompanying Drawings.
In witness whereof, I, the said John Imray, have hereunto set
my hand and scal, this Twenty-second day of November, in the
year of our Lord One thousand eight hundred and seventy-
five.