IMPROVED APPARATUS FOR CUTTING SCREW THREADS ON OR IN BOLTS AND NUTS
Year: 1877

page_text: LETTERS PATENT to Thomas Graham Elliott, of Leeds, in the County of
York, for the Invention of "IMPROVED APPARATUS FOR CUTTING SCREW
THREADS ON OR IN BOLTS AND NUTS."
Sealed the 11th June 1878, and dated the 24th December 1877.
"
IMPROVED
PROVISIONAL SPECIFICATION left by the said Thomas Graham Elliott at
the Office of the Commissioners of Patents on the 24th December 1877.
THOMAS GRAHAM ELLIOTT, of Leeds, in the County of York.
APPARATUS FOR CUTTING SCREW THREADS ON OR IN BOLTS AND NUTS."
The object of this Invention is to enlarge the means at present available for
adjusting the screw-cutting tools or dies used in cutting the threads of bolts and
nuts.
Supposing the chuck of the screw-cutting lathe to be fitted with tools for
threading screw bolts, I form on the stem of these radial cutters rack teeth, into
which take sector racks constituting the ends of rock levers which give the requisite
feed motion to the cutters. The tails of these rock levers are fitted with bowles
which lie in countersunk inclined grooves formed in a cone, which is free to slide
upon the hollow spindle of the chuck. By the forward end-way motion of this
cone the cutters are advanced to their work, and the amount of motion which they
can receive is limited by the proportions of the cone.
To allow for the wearing away of the tools, and also to adapt them for cutting
bolts of various diameters, it is only necessary to shift them forward or backward
one or more teeth, and a rough adjustment is thereby obtained, the full adjustment
and the feed motion being provided for as heretofore by the sliding cone.
For operating the adjusting cone I provide the following contrivance :-The
fork which embraces the annular recess made in the rear of the sliding cone is
formed of a tail piece that constitutes a sector rack, and vibrates between fixed
adjustable stops that determine the amount of its rocking motion and consequently
the amount of traverse of the cone. Into this rack gears a pinion formed on the

page_text: boss of a mitre wheel, which is in gear with a pair of mitre wheels mounted loosely
on a hollow driving shaft that lies parallel with the chuck spindle. Between these
mitre wheels, and secured to the hollow shaft by a transverse pin which passes
through slots in the shaft, is a friction clutch, which is brought into contact with
either of the two mitre wheels, and serves to give rotary motion thereto The 5
friction clutch is shifted by means of a hand lever, which is connected to its
transverse pin by means of a rod passing through the hollow driving shaft. A
counterweight, also connected to this rod, serves to move the clutch in an opposite
direction to the hand lever.
For screwing nuts it will be obvious that the same principle of adjustment for 1
the male dies or cutters may be employed as that explained with reference to the
dies or cutters for the screw bolts.
+
$
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas Graham Elliott in the Great Seal Patent Office on the
24th June 1878.
THOMAS GRAHAM ELLIOTT, of Leeds, in the County of York. " IMPROVED
APPARATUS FOR CUTTING SCREW THREADS ON OR IN BOLTS AND NUTS."
The object of this Invention is to enlarge the means at present available for
adjusting the screw-cutting tools or dies used in cutting the threads of bolts and
nuts.
Supposing the tool holder or die box of the screw-cutting machine to be fitted
with tools for threading screw bolts, I form on the stem of these radial cutters rack
teeth, into which take sector racks constituting the ends of rock levers which give
the requisite feed motion to the cutters. The tails of these rock levers are fitted
with bowles, which lie in countersunk inclined grooves formed in a sliding block,
which is carried by the hollow spindle of the tool holder By the forward endway
motion of this sliding block the cutters are advanced to their work, and the amount
of motion which they can receive is limited by the traverse of the sliding block.
To allow for the wearing away of the tools, and also to adapt them for cutting
bolts of various diameters, it is only necessary to shift them forward or backward
one or more teeth and a rough adjustment is thereby obtained, the finer adjustment
and the feed motion being provided for as heretofore by the sliding block.
In Sheet I. of the accompanying Drawings,―
Fig. 1 shews in longitudinal sectional elevation a screw-cutting machine fitted
according to this Invention; Fig. 2 is a transverse section of the same taken in
the line 1-2 of Fig. 1; Fig. 3 is a sectional plan taken in the line 3-4 of Fig. 1. ·
-Fig. 4 is an end elevation with the slide for carrying the work removed.
Fig. 5 is a front elevation of this slide detached, and Fig. 6 is a plan view of the
same.
C

page_text: a hollow spindle B, carrying at one end the tool holder or die box B¹, which is
fitted with threading tools or dies b according to this Invention. The other end of
the spindle B is fitted with a spur wheel C, which gears into a pinion C¹, keyed
on to a hollow shaft D mounted in the framing A immediately below the tool
holder spindle and constituting the main driving shaft of the inachine, it being
fitted with belt pulleys D' which are driven by a band from any prime mover.
This driving shaft D serves to impart through the gearing a continuous rotary
motion to the tool holder spindle D.
Inserted in the hollow shaft D is a rod E, which is slotted at its inner end to
receive a transverse key e which passes through slots in the shaft D (made parallel
to its axis), and serves to connect with the rod E a sleeve E¹ that surrounds the
spindle D. This sleeve is coned at its opposite ends and forms a friction clutch,
which engages with two bevil pinions d, d, mounted loosely upon the shaft D and
coned at their bases to receive the fiction clutch, as shewn at Fig. 3. In gear
with these pinions is a bevil wheel d², which is keyed to a short crank shaft D³,
carrying a crank pin d³, the use of which is by the reciprocating motion which it
receives from the shaft D to impart an endway motion to the threading tools b.
This crank pin d³ enters a slot in the lower end of a rock lever F, and formed
longitudinally thereof. This lever lias for its fulcrum a transverse shaft F¹, carried
in bearings in the main framing Keyed to this shaft is an arm F², which is con-
nected adjustably with the upper end of the rock lever F, as shewn best in the
detached view Fig 7, that lever being forked at its upper end to receive a pivotted
nut f, through which a coupling screw f1 from the arm F passes
It will now he understood, that, as the lever F is rocked by means of the crank
pin in either direction, it will through the arm F2 impart an axial motion to the
shaft F On this shaft is also koyed a forked casting F³, the arms of which carry
antifiiction bowles; these bowles enter an annular groove cut in the rear of the
sliding block G, which is free to move endwise upon the tool holder spindle. This
block is formed with longitudinal inclined grooves to receive the bowles carried by
the tails of three rock levers 6' which are pivotted in radial slots in the tool
holder B. The forward end of these rock levers carry spur teeth which gear with
rack teeth formed on the stems of the cutting tools or dies b, which tools are fitted
to slide in radial slots cut in the face of the tool holder, and are held in place by
the cap, plate, or cover of the tool holder
As the block G is moved in the direction of the arrow, Fig. 1, under the pressure
of the bowles of the arms F, keyed to the rock shaft F¹, the rock levers b will be
caused to press the tools b inwards and bite the work submitted to their action
The bolt to be threaded is made fast between the movable jaws h of the work
holder H as usual, and it is gradually advanced towards the cutters by means of
the pinion I actuated by the hand levers 1', and gearing into a rack formed on the
under face of the slide or work holder H, as in the ordinary sci
sci ew-cutting
machines
I have stated that the rotation of the tool holder, and consequently of the
creading tools b is continuous; it is necessary therefore under such circumstances,
as is well understood, to withdraw the threading tools out of contact with the
work when it is required to draw back the work. This is effected by drawing
back the block G, the slots in which are formed with an overlapping flange to
embrace the bowles of the rock lovers b¹, thus, as the block G is withdrawn it will
tip the levers 6' and move back the threading tools clear of the work. It is to
obtain this to-and-fro motion of the sliding block G that the conical friction
clutch E' is used, its office being to impart rotary motion alternately to one or
other of the bevil pinions d, d. When the friction clutch is in contact with the
pinion D, as shewn in Fig. 3, the rotation of the spindle D being in the direction
of the arrow, Fig. 1, the bevil wheel & will rotate in the direction of the arrow
and carry down the crank pin to the bottom of the slot in the rock lever F, at
which time the upper end of that lever will arrive at its furthest position to the

page_text: left. Following this motion of the rock lever the block & will make its nearest
approach to the tool holder, and thus the threading tools will have made their
deepest cut. That having taken place the attendant will now be required to shift
the direction of rotation of the bevil wheel d² and move back the sliding block G,
as above explained, and thereby withdraw the threading tools. To this end the
attendant holding the weighted lever K presses it inwards, and thereby through
a fork K' on the fulcrum rod of the lever, connected a strap with the sliding
rod E, forces the friction clutch E¹ out of contact with the pinion d, and into
contact with the pinion d', thus reversing the direction of rotation of the bevil
' wheel d The crank pin d³ will now rock the head of the lever F towards the
right, bring back the sliding block G to its starting position, and cause the rock
levels to lift the thread-cutting tools clear of the work.
Supposing now it is required to cut a thread on a bolt of about two-thirds the
diameter of that shewn at Fig. 1, the attendant will, by shifting the cutters inwards
the distance of one tooth, and then connecting them as before with their respective
rock levers, bring the cutters within close range of the bolt to be threaded. The
advance of the sliding block G will complete the adjustment, and give the requisite
feed to the tools.
If, on the contrary, a bolt of larger diameter is required to be threaded the
cutting tools will be shifted back, say, a tooth, and a way will thus be opened for
the advance of the bolt within the action of the cutters These advantages, it will
be understood, are gained by my improved mode of connecting the cutting tools or
dies with the rock levers.
When the threading of nuts is to be performed in this machine I use in place of
the form of cutting tool, shewn in Fig 1, a tool similar to that shown detached at
Figures 8, and operate it in the way already explained with reference to the tools b.
The mechanism for giving the rocking motion to the lever F admits of various
modifications; one of these I have shown for example in Sheet II. of the
Drawings.
Fig. 9 is a vertical section, and Fig. 10 is a sectional plan view of this part of the
mechanism.
Fig. 11 shows the rock lever in side elevation and the gearing for operating the
same.
The rock lever F instead of being driven by a crank pin is formed at its lower
end with rack teeth, which gear into a worn 1 keyed to a back shaft 2, having its
bearings in the main framing. The rock lever in this instance carries the anti-
fiiction bowles, which give the traverse motion to the sliding block G. The back
shaft 2 also carries two spur pinions 3, 4, which gear the one directly with the spur
pinion 5, and the other through an intermediate pinion 4* with the pinion 6. The
pinions 5 and 6 are mounted loosely on the driving shaft D and are driven by
friction clutches, the rod E in this case being fitted with two friction clutches E¹, E³,
by means of which either spur pinion 5 or 6 is put into action by giving a slight
endway motion to the rod E, as before explained; thus, according to whether the
worm wheel is driven direct from the shaft D or through the intermediate pinion,
its motion will be to the right or left of Fig. 11, and a corresponding rocking motion
will be given to the lever F.
In order to keep up a continuous lubrication of the threading tools the machine
is provided (see Sheet I. of the Drawings) with a pump L, which consists of a
plunger working in a fixed cylinder under the action of an excentric L¹ keyed on
the driving shaft D. From this pump L proceeds a pipe l, which by branches 11, 1,
leads to the interior of the tool holder spindle. The lubricating material discharged
into this spindle runs into and through the tool holder and finds its way into a
trough A, constituting a bracket support for the work holder H, whence the waste
or overflow is conducted back to a receptacle in connection with the pump.
Having now set forth the nature of my Invention of "Improved Apparatus for
Cutting Screw Threads on or in Bolts and Nuts," and explained the manner of

page_text: carrying the same into effect, I wish it to be understood that under the above in
part recited Letters Patent I claim,―
First. The means above described for giving an increased range of adjustment to
the tools or dies used in cutting screw threads.
Secondly. Traversing the sliding block G by means of a forked rock lever
actuated by reversing friction gear under the control of the attendant, as and for
the purpose above described.
In witness whereof, I, the said Thomas Graham Elliott, have hereunto set
my hand and seal, the Twenty-first day of June, in the year of our Lord
One thousand eight hundred and seventy-eight.
THOMAS GRAHAM ELLIOTT. (L.S.)