Improvements in Screw Cutting Machines.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Screw Cutting Machines.
I, HENRY EDWARD COY, Machinist, of 653 South Street, in the City of Toledo,
Lucas County, State of Ohio, in the United States of America, do hereby declare
the nature of this invention and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement :-
My invention relates to that class of screw threading or cutting machines in
which the spiral groove is cut upon the blank or bolt by means of a rotary, toothed
cutter, and the object of my invention is to improve, cheapen and simplify such
machines and more particularly to provide the rotary, toothed cutter of such.
machines with a forward feed, varied and proportioned in its rapidity to the depth
of the cut. of such cutter and the angle of its line of travel to the axis of the bolt to
be cut to provide means whereby the rotary, toothed cutter may be permitted to
slip upon its arbor when the strain upon the cutter and its bearings become too
great, and to so arrange the relative proportions of said cutter and its driving
mechanism, as to avoid undue strain upon and wear of the parts, and dispense with
the necessity for clearing the cutter from the bolt before its return to its starting
point.
I attain these objects by means of the mechanism hereinafter described and
shown in the accompanying drawings made part hereof, in which
Fig. 1, is a side elevation of my machine.
Fig. 2, an end elevation of the same viewed from the right in Fig. 1.
Fig. 3 a portion of lever designed to start and stop the mechanism provided to
give forward feed to the cutter of my machine.
Fig. 4, a plan view of my machine.
Fig. 5, an enlarged end view of a portion of my machine as seen from the left in
Figs. & 4.
Fig. 6, vertical cross section on line A A (Fig. 4).
Fig. 7, enlarged side view of that part of my machine designed to give a variable
forward feed to the rotary cutter together with tripping device designed to throw
into and out of gear the mechanism giving forward feed to the rotary cutter and
causing the return of the cutter to its starting point.
Fig. 9, end view of same partly in cross section.
Fig. 8, tripping dogs, hereinafter referred to, in detail.
Fig. 10, detail of former, controlling depth of cut of rotary cutter and giving
taper to the screw.
Figs. 11 & 12, views of rotating, toothed chasing-tool, and screw in different
stages of manufacture.
Like letters of reference indicate like parts throughout the several views.
My machine is mounted upon a stout frame or table. A spindle, a, carrying the
bolt to be threaded, is provided with a socket to receive the head of bolt and is
driven directly by pulley A. Spindle a is made adjustable longitudinally, so that
it may be made longer or shorter, according to the length of bolt to be threaded.
Bolt is braced and prevented from yielding or bending from the pressure of the
cutter, by means of guide-blocks 61 on travelling head i. Rotary toothed cutter c,
which resembles a disk cut transversely from a large, multiple-threaded screw,
rotates horizontally, the upper corners or angles of the teeth of the cutter forming
a series of chasing or cutting edges. (See Figs. 11 & 12.)
In Figs. 1, 4, 11 and 12, the upper side of bolt 6 in its revolution moves toward
the cutter c which rotates so that the shavings are taken off toward the point or
end of the bolt.
At the beginning of the operation, a blank bolt b, to be pointed and threaded

page_text: being in place, cutter c is set touching the bolt, and so that the circle described by
the cutting edges or corners of the teeth of cutter c touches the extended line of the
axis of the bolt. Bolt 6 being caused to revolve on its axis, cutter c is also rotated
at such rate of speed that for each revolution of the bolt b, cutter c rotates the
distance of from the face of one of its teeth to the corresponding face of the next
tooth, allowing also for the forward travel of cutter c. The rotary, toothed cutter c,
besides its rotary motion on its own axis, moves to and fro in the direction of the
length of the bolt, and moves in the segment of a circle of which the centre of
trunnion (Figs. 1, 4, 5 & 6) hereinafter referred to, is the centre. The rotation
of the toothed cutter on its own axis causes its chasing or cutting teeth to engage
successively the spiral cut or groove as it is formed so that the bolt and cutter
revolve in relation to each other after the manner of worm and worm-wheel in
worm-gearing. The motion to and fro of the cutter, in the direction of the length
of the bolt, enables the cutter to travel along the bolt from the point toward the
head cutting the thread as far as may be desired and then to return to the starting
point. The motion of the cutter in the segment of a circle, of which trunnion k² is
the centre, enables the cutter to approach and recede from the axial line of the
bolt b, so that the screw is pointed and given any desired taper.
At the beginning of its cut, while forming the point upon bolt b, the cutter makes
a somewhat deeper cut than during the remainder of the operation, and travels at
an angle from the axis of bolt b, so that at this part of the operation the forward
travel of the cutter along the bolt must necessarily be slower than when a more
shallow cut is made, and when the forward travel of the cutter is parallel with the
axis of the bolt. The mechanism by means of which these several motions of the
cutter, together with its variable forward feed, are obtained I will now proceed to
describe.
C
Cutter is mounted upon vertical shaft d, (see Figs. 1 & 6) provided with worm-
wheel C, which engages worm f upon shaft g, which worm extends along said shaft
as far as the worm-wheel travels and as far as the bolt is to be cut. Shaft g has a
pinion engaging a corresponding pinion ¹ on spindle a driven by pulley A. The
rotation of the cutter on its own axis is, accordingly, communicated through train
consisting of pulley A, spindle a, pinion ', pinion ½, shaft g, worm f, worm-wheel e
and shaft d.
Shaft d and worm-wheel e are contained in box k, which oscillates in a vertical
plane having for the centre of its oscillation trunnions on the sides of box k which
are journaled in bearings 2 on head i. Box is provided with an arm, k', which
engages, by means of screw 1, a roller m arranged to travel in the direction of the
length of the screw to be cut. Arm is held in close contact with the carriage of
roller m by spring o attached at one end to the travelling head i and at the other
end to arm by means of eye-bolt o¹.
it
By depressing or elevating roller m box k through its arm k is tilted, and
cutter c is thrown from or toward bolt b, as the case may be, thus providing for
giving taper to bolt b. Plate (Figs. 1, 4 & 10) is a former or roller guide upon
the under edge of which, n', roller m travels. This plate is supported at one end
by standard n² and at the other end by and in an opening in head i, through which
passes. Surface n' is designed to give the required size, taper and general shape
to the screw to be cut, the roller m in travelling over surface n¹ causing cutter c to
tilt to or from the bolt b, in conformity with the lines and undulations of surface n³,
without interruption of the rotary or forward movement of the cutter.
Head, which supports and carries the oscillating box k, with the cutter and its
shaft and worm-wheel, together with the guide-block b, spring o and one end of
is mounted upon standards projecting upwards from carriage which
slides to and fro upon shears or way ³. Head i is provided with projecting sleeves i*
in which slips threaded shaft g, and which sleeves serve as a support and guide for
the extremity of that shaft and as a protection to its thread or worm against cuttings
from bolt b. Carriage is provided with rod p, leading and attached to sliding-
which rod and bar may be regarded as part of the carriage, being in line
former
bar
n,

page_text: therewith and all sliding to and fro together. Bar at its outer extremity is split,
and in the cleft near the end of the bar is placed roller r. In the cleft of bar qis
placed vertically a cam or frame s having three sides or, rather, edges, being in
general outline triangular, the edge nearest the carriage being vertical, the bottom
horizontal and the remaining edge a line at varying angles to the vertical and
against which roller rests. The raising of frame s, vertically, causes roller r to
travel along the inclined planes of the frame, pulling with it bar q, rod p, carriage
and its appendages, giving forward horizontal travel to the cutter c along bolt b.
The more obtuse the angle to the vertical of the plane presented to roller the
more rapid will be the motion of the roller and its train of appendages horizontally,
and the more acute the angle the slower will be the roller's forward travel.
ין
Thus, it will be seen that with the frame s moving vertically at a uniform rate of
speed, the motion imparted to roller, horizontally, may be varied as desired by
variation of the angles of the inclined planes upon which the roller travels. In the
drawings, (Fig. 7) face s¹ is at such angle to the vertical as will cause roller r,
with its attachments, to advance rapidly, bringing the cutter forward against the
end of the blank bolt; face 2 then causes the cutter to advance slowly while the
cutter is forming the point of the screw and moving at an angle away from the axis
of the bolt; then face 3 advances the cutter more rapidly while the thread is
forming on the bolt. The lift of frames is obtained by means of a rack t (Figs. 1
and 7) on its vertical edge, engaged by a pinion t' (Figs. 7 and 9) fixed on shaft t²,
which shaft is caused to revolve by a worm-wheel ³, (Figs. 1, 2, 4 & 9), driven by
worm ton shaft 5 having pinion which engages pinion t on the driving shaft of
the machine. (See Fig. 4.) Worm-wheel (Fig. 9) is loose on its shaft, but is
provided with a clutch 7, (Figs. 1, 2, & 9) which revolves with and slides upon its
shaft 2. Clutch u is thrown into and out of gear by means of rod u' passing
through and moving longitudinally in shaft 2 which is hollow. Rod u' is provided
with a spur u² which projects through a longitudinal slot in shaft 2 engaging and
carrying with it clutch u. Coiled springs ³ upon rod u serve to hold the rod in
place, though permitting its motion longitudinally. Frames being at its lowest
point, and clutch u being thrown into gear, the frames is lifted to the desired
height by means of rack and pinion t, t¹. When the frames has been lifted a
suitable distance, the clutch is automatically disengaged from worm-wheel t³,
permitting frames to fall by its own weight to its starting point, reversing the
motion of shaft t2 and clutch u during its fall.
At the top of plate s is fixed vertical rod v, provided with a movable finger v',
which may be set at any desired point on the rod. This finger embraces loosely,
vertical rod v² which carries a collar v³ adapted to be set at any point on its rod.
Rod is loosely attached, pivotally, to one arm of a bell-crank lever, v', the other
arm of which is forked and embraces rod a working against a shoulder on the
rod u¹. When frames has carried its rod v to a proper height, finger v strikes
collar on rod v2, the horizontal arm of lever is lifted and the vertical arm
pushes rod a' which disengages clutch u. Thus, it will be seen, the release of the
clutch may be obtained at any point in the operation of cutting the bolt, by adjust-
ment of finger and collar on their respective rods, permitting the frames to
fall to its starting point. As frames falls, carriage, with its attachments, is
drawn back to its starting point by means of a spring, or cord and weight plas
indicated at extreme left of Fig. 1. For the purpose of preventing the concussion
and jar resulting from the fall of frame s, rod v, at its upper end, is provided with a
piston moving in a dash-pot, v, in the usual manner.
At its lowest point frames rests in loop or stirrup w, (Figs. 1, 2, 7 & 9.)
suspended from arms w³, projecting radially from shaft w²; this shaft is oscillated by
means of lever (Figs. 1, 2 & 4.) provided with connecting rod a', which is pivoted
at one end to the lever and at its other end to arm or crank ², on shaft w², (see
Fig. 3). Upon shaft w², is a radially projecting lug y, (see Figs. 7 and 9) which
when depressed by the rotation of its shaft, engages a collar y¹, on the lower end of
rod 2. To start the cutter forward, the operator throws to the left, (Fig. 1) the

page_text: t
:
.
upper end of lever, which, through rod a¹, arm ², shaft w², lug y and rod 2, pulls
down the horizontal arm of bell-crank lever v', causing its vertical arm to pull
clutch u into gear by means of rod . By the same movement of lever a stirrup w,
through rod, arm 2, shaft w² and arms w', is lifted, carrying with it frames,
which by this rapid lift, through face s', and roller pulls carriage 2 with the
cutter e quickly forward to the end of bolt b so, that cutting is begun without loss
of time. This rapid upward lift of frames is permitted notwithstanding clutch u
is in gear, the clutch being adapted to run free when rotated rapidly through rack
and pinion t, t¹, by lifting frames. For the purpose of holding clutch in gear
until released by the throw of bell-crank lever v', I provide a dog z, (see Figs. 2,
7, 8 & 9.) pivoted near its middle, one end of which has a notch which engages the
lug on bell-crank lever et, the other end being forked and engaging loosely rod v².
On this rod, immediately below dog z, is a collar secured to rod 2 so that when
rod is lifted collar 22 strikes the forked extremity of dog 2, causing its notched
end to tilt downward, releasing lug' on bell-crank lever which, through rod u',
releases clutch u. When rod is pulled downward, pulling clutch u into gear,
lug is raised and dog tilts back so that its notch again engages the lug on the
bell-crank lever v1, which, with the clutch u, is thus held securely in place until the
dog is again tripped by the lifting of rod v2.
When frames falls, and while carriage with its load is travelling back to its
starting point, drawn by cord and weight p', worm-wheel e (Fig. 6) rolls upon
worm fon shaft g, as a pinion rolls upon a fixed rack; and in like manner cutter c
rolls upon bolt, the teeth of the cutter falling into the spiral groove cut upon the
now completed screw. To admit of this backward travel of carriage ² and the
backward revolution of cutter e and worm-wheel e, as well as to prevent undue
strain and wear upon and the stripping of these parts, it is necessary that the lead
of the threads on shaft and screw shall be substantially the same in each; in
other words, that the relation of worm-gear e f and bolt and cutter be to each other,
shall permit the worm-wheel and cutter to roll together upon the same shaft, upon
their respective screws as pinions roll, upon fixed racks. It will be seen, however,
that while the point of the screw is being cut and while the cutter is moving at an
angle to the axis of bolt b, the harmony of movement between cutter c and worm e
is slightly broken. To obviate this difficulty and to prevent undue strain or wear
upon the cutter or the worm-gearing eƒ during this part of the operation, cutter c
is adapted when the strain becomes too great, to slip upon its arbor and thus to
adjust itself to the thread it is cutting; to accomplish this, cutter c runs loose on its
arbor and is pressed against its seat c', by a friction-block c³, between which and a
regulating nut c³, at the top of shaft d, is interposed spring c. By means of nut c³,
pressing on friction-block 2 through spring ct, adjustment of friction is had and any
required degree of rigidity of the cutter on its bearings is obtained. The same
results may be obtained by applying the friction device to worm-wheel e or to
pulley ', but I prefer the method here shown.
Means for dispensing with any motion of my cutter, save the rotary motion, will
suggest themselves to skilled mechanics, it being quite practicable to cause bolt b
to advance and recede longitudinally and laterally at a variable rate of speed while
the thread is forming. A rotary cam or other mechanism for transforming a motion
of uniform speed to a motion of irregular speed may also be substituted for the
reciprocating frame Sq but such mechanism would obviously be the mechanical
equivalent of the herein described device, and I do not therefore limit my invention
to the variable feed of the cutter alone nor to a particular device for imparting a
variable rate of feed thereto.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is
1. A screw-cutting machine having the rotary, toothed cutter c, adapted, by
means of the mechanism, substantially as described, to feed in the direction of the

page_text: length of the bolt to be cut, at a variable rate of speed, substantially as shown and
described, for the purpose specified.
2. In a screw-cutting machine the rotary, toothed cutter and its supporting
mechanism, substantially as described, in combination with the frame or cam having
a face or faces adapted to give forward motion to such cutter at a variable rate of
speed, substantially as shown and described, for the purpose specified.
3. In a screw-cutting machine, the cam or frames having face >', adapted to
bring the cutter rapidly forward to the end of the bolt, face s², adapted to cause
the cutter to move slowly forward while the point on the screw is forming, and
faces, adapted to cause the cutter to advance more rapidly during the remainder
of the cut, substantially as shown and described, for the purpose specified.
4. In a screw-cutting machine, the rotary, toothed cutter and its carriage in
combination with cam or frame s having rack t and the train of gearing intermediate
the driving pulley of said machine and said rack, substantially as shown and
described for the purpose specified.
5. In a screw-cutting machine, the rotary, toothed cutter c, and its train of
gearing intermediate said cutter and the driving pulley in combination with the
cam or frames and its train of gearing intermediate said cam or frame and the
driving pulley of said machine, substantially as shown and described for the purpose
specified.
6. In a screw-cutting machine, the rotary cutter and its carriage, the cam or
frame adapted to give forward motion to such cutter and a clutch in the train of
gearing intermediate said cam or frame and the driving pulley of said machine, in
combination with suitable tripping mechanism, adapted to disengage said clutch
when said cutter has completed its cut, whereby said carriage and cam or frame are
permitted to return to their starting point, substantially as shown and described,
for the purpose specified.
7. In a screw-cutting machine, the rotary cutter and its carriage, the cam or
frame adapted to give forward motion to said cutter, and a clutch in the train of
gearing actuating said cam or frame, in combination with a hand-lever adapted to
simultaneously start said cam or frame forward and to throw into gear said clutch,
substantially as shown and described for the purpose specified.
8. In a screw-cutting machine, the rotary cutter c and cam or frame s, in
combination with bell-crank lever, adapted through adjustable connections, inter-
mediate said lever and said cam or frame, to throw into or out of gear a clutch in
the train of gearing actuating, said cam or frame, substantially as shown and
described, for the purpose specified.
9. In a screw-cutting machine, the rotary, toothed cutter c, adapted, by means of
the mechanism, substantially as described, to advance toward and recede from bolt b
laterally, the former n, and the mechanism intermediate said former and said cutter,
in combination with the cam or frame s adapted, by means of the mechanism, sub-
stantially as described, to impart forward motion to said cutter at a variable rate of
speed, substantially as shown and described for the purpose specified.
10. In a screw-cutting machine, the rotary, toothed cutter having in its driving
gear a worm-wheel, said cutter being adapted by means of the mechanism, substan-
tially as described, to cut a thread of such lead that said cutter and said worm-
wheel may roll together each upon its own screw, as a pinion upon a fixed rack,
substantially as shown and described, for the purpose specified.
11. In a screw-cutting machine, the rotary, toothed cutter c, adapted, by means
of the mechanism, substantially as described, to slip upon its bearings, substantially
as shown and described, for the purpose specified.
12. In a screw-cutting machine, the combination of the rotary, toothed cutter c
with seat c¹, friction-block c², adjusting nut c³ and spring e, substantially as shown
and described, for the purpose specified.
13. In a screw-cutting machine, the rotary, toothed cutter, adapted, by means of
the mechanism, substantially as described, to slip upon its bearings and to cut a

page_text: thread of substantially the same lead as the worm-gear in its driving mechanism,
substantially as shown and described for the purpose specified.
14. In a screw-cutting machine, the rotary, toothed cutter c, adapted, by means
of the mechanism, substantially as described, to slip on its bearings, and to cut a
thread of the same lead as the lead of the worm-gear in its driving mechanism, in
combination with the cam or frames adapted, by means of the mechanism, substan-
tially as described, to give variable, forward feed to said cutter, substantially as
-shown and described, for the purpose specified.
15. In a screw-cutting machine, the rotary, toothed cutter c, adapted, by means
of the mechanism, substantially as described, to slip on its bearings, and to cut a
thread uniform in its lead with the lead of the worm-gear in its driving mechanism,
in combination with the cam or frames adapted, by means of the mechanism, sub-
stantially as described, to give a variable, forward feed to said cutter, and the
former n adapted by means of its conformation, to give lateral motion to said cutter
and suitable taper to the finished screw, substantially as shown and described, for
the purpose specified.
16. In a screw-cutting machine, the rotary, toothed cutter c, in combination with
worm-gearing ef, the worm f having the same lead as the screw thread designed
to be cut by said cutter, and said worm extending along its shaft as far as the
screw is designed to be cut, substantially as shown and described for the purpose
specified.
17. In a screw-cutting machine, the rotary, toothed cutter c and its carriage, in
combination with the cam or frame s, adapted by means of the mechanism, substan-
tially as described, to give a variable forward feed to said cutter, and cord and
weight, pl, adapted, by means of the mechanism, substantially as described, to draw
said carriage back to its starting point upon its release from the pull of said cam or
frame, substantially as shown and described, for the purpose specified.
18. In a screw-cutting machine, the rotary, toothed cutter c, adapted, by means
of the mechanism, substantially as described, to slip on its bearings, and to cut a
thread of the same lead as the lead of its driving worm-gear, in combination with
pulley A and the train of gearing, intermediate said pulley and said cutter, spindle a,
brace and guide-block 6', cam or frames having faces s', s², and s³, and the train of
gearing actuating said cam or frame, the tripping mechanism adapted, by means of
the mechanism, substantially as described, to release said frame from its said train
of gearing, lever x, adapted, by means of the mechanism, substantially as described,
to engage said frame with its train of gearing, and cord and weight p³, substantially
as shown and described, for the purpose specified.
Dated the 17th day of March 1891.
J. C. CHAPMAN, Fel. Inst. Patent Agents,
70, Chancery Lane, London, W.C.