Improvements in Indicating Apparatus for Screw Cutting Lathes
Year: 1893

page_text: Date of Application, 8th Mar., 1893
Complete Specification Left, 8th Dec., 1893-Accepted, 27th Jan., 1894
PROVISIONAL SPECIFICATION.
Improvements in Indicating Apparatus for Screw Cutting Lathes
We, HENRY GEORGE MARSHALLSAY of 120 Victoria Road, Aldershot, Hants,
Dentist, and THOMAS RICHARDSON of 13 Cavendish Road, Aldershot, aforesaid,
Mechanical Dentist, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object to provide means whereby an indication may be
given of the proper moment for placing in gear with the leading screw the feed nut
of the saddle or carriage that carries the cutting tool in a screw cutting lathe in
order to make the successive cuts necessary to form a screw thread, specially in
cases where the pitch of the thread of the leading screw is such that the number of
turns it makes per inch is not a multiple of the number of turns per inch in the
thread to be produced.
For this purpose there is connected to the leading screw by some convenient
connection, an indicator that is operated from the leading screw in such a manner
as to give an audible as well as a visible indication of the proper times at which
the engagement between the leading screw and the feed nut can be made so as to
ensure that the screw cutting tool operates correctly.
In one arrangement of apparatus according to our invention for this purpose, the
indicator comprises a dial marked with figures corresponding to inches of travel of
the saddle and provided with fingers or plungers or equivalent parts in positions
corresponding to given positions of the screw cutting tool longitudinally of the
lathe bed, the said fingers, or plungers or equivalent parts being adapted to be
raised and retained in their raised positions, or lowered and retained in their
lowered positions according to requirement for the purpose to be presently
explained.
About the centre of the dial there is mounted a radial arm that is suitably driven
On the free end of this
from the leading screw so as to turn about the said centre.
arm is pivoted a star wheel which is normally prevented from rotating by means of
a lever or catch kept against the star wheel by means of a spring but which when
the star wheel comes in contact with a raised finger, plunger or its equivalent, will
permit the star wheel to move through one tooth by overcoming the spring which
will immediately return the catch or lever into position against the star wheel
thereby holding it against rotation about its axis until it again comes in contact
with a finger, plunger or equivalent.
By the movement of the locking lever by means of the star wheel as described,
a small hammer, which may be carried by means of a spring mounted on the lever,
will be caused to strike a bell. Conveniently the indicator may be driven from the
The dial may be
leading screw through the medium of a worm and wheel.
mounted on a hinge provided with a curved bar passing through a slot in the frame
to which the dial is pivoted, a set screw being provided so that the dial may be
fixed at any convenient angle to enable it to be readily seen by the person in charge
of the machine.
In some cases motion may be communicated from the leading screw to the worm
through the medium of bevel gear, the connection between the leading screw and
the driving wheel of the bevel gear being made by means of a friction clutch.
This clutch, according to one arrangement, is tightened up by means of a nut wheel
having an internal flange that bears against an external flange on a female conc
which is tightened on to a male cone by turning the nut wheel in one direction and
freed by turning the nut wheel in the reverse direction.

page_text: The dial is made adjustable about its axis irrespective of the driving gear so
that it may be made to assume a correct position for starting on any given work.
Dated this 8th day of March 1893.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Indicating Apparatus for Screw Cutting Lathes..
We, HENRY GEORGE MARSHALLSAY, of 120 Victoria Road, Aldershot, Hants,
Dentist, and THOMAS RICHARDSON of 13 Cavendish Road, Aldershot, aforesaid,
Mechanical Dentist, 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:-
This invention has for its object to provide means whereby an indication may be
given of the proper moment for placing in gear with the leading screw the feed nut
of the saddle or carriage that carries the cutting tool in a screw cutting lathe in
order to make the successive cuts necessary to form a screw thread, specially in
cases where the pitch of the thread of the leading screw is such that the number
of turns it makes per inch is not a multiple of the number of turns per inch in the
thread to be produced.
For this purpose there is connected to the leading screw by some convenient
connection, an indicator that is operated from the leading screw in such a manner
as to give an audible as well as a visible indication of the proper times at which the
engagement between the leading screw and the feed nut can be made so as to
ensure that the screw cutting tool operates correctly.
In the accompanying drawings,
Figs. 1, 2 and 3 are respectively front, rear and side elevations, and Fig. 4 a
vertical cross section, partly in elevation, illustrating apparatus for this purpose
constructed according to this invention.
Fig. 5 is a part rear elevation of the dial with the back plate and attached parts
removed.
Fig. 6 is a part plan of the apparatus.
Fig. 7 shows in plan a clutch and bevel gearing for transmitting motion from the
leading screw of a lathe to the indicating portion of the said apparatus.
Fig. 8 shows the said clutch in longitudinal section.
Figs. 9 to 16 inclusive are detail views hereinafter referred to.
The apparatus comprises a dial 1 marked with figures as shown, corresponding to
inches of travel of the saddle of the lathe, and provided with fingers 2 or equivalent
parts in positions corresponding to given positions of the screw cutting tool
longitudinally of the lathe bed, the said fingers, or equivalent parts being adapted
to be raised and retained in their raised positions, or lowered and retained in
their lowered positions according to requirement for the purpose to be presently
explained.
For this purpose each finger 2 in the example shown, is pivoted on a pin 3
within a recess 3ª in the dial and acted upon by a spring 4 so as to hold it either'
in the raised or lowered position as shown at the upper and lower portions respec-
tively of Fig. 4. 4 is a ring secured to the back of the dial for holding the
springs 4 in place.
5 is a radial arm shown more clearly in front and side elevations in Figs. 9 and 10
respectively. It is suitably driven from the leading screw through a spindle 5* on
which it is fixed, and is arranged to turn about the centre of the dial. On the
free end of this arm is pivotted a star wheel 6 which is normally prevented from
rotating by means of a lever or catch 7 (Figs. 9 and 11) which is pivoted to the

page_text: arm 5 at 7 and is kept against the star wheel by means of a spring 8 but which
when the star wheel comes in contact with a raised finger 2, will permit the star
wheel to move through one tooth by overcoming the spring, which will immediately
return the lever or catch 7 into position against the star wheel thereby holding_it
against rotation about its axis until it again comes in contact with a finger. By
the movement of the locking lever by means of the star wheel as described, a small
hammer 9 which may be carried by means of a spring 10 mounted on the said lever
or catch 7 as shown, will be caused to strike a bell 11 fixed on the dial.
Conveniently the indicator arm 5 may be driven from the leading screw through
the medium of a worm 12 (Figs. 2 and 4) and a worm wheel 13 which is fixed upon
the spindle 5. The dial is provided with a boss 1 carrying a plate 14 which may
be hinged or jointed by eyes 15 to a suitable frame or support 16, and be provided
with a curved bar 17 passing through a slot in the said frame 16, a set screw 18
being provided so that the dial may be fixed at any convenient angle to enable it to
be readily seen by the person in charge of the machine.
The dial is made adjustable about its axis irrespective of the driving gear, so
that it may be made to assume a correct position for starting on any given work,
and also to enable screws to be cut whose threads per inch are not a multiple of the
highest number indicated on the dial then in use.
For this purpose the back of the dial 1 is in the example shown, formed with
a number of holes 1", Figs. 4 and 5, in which a pin 14ª carried by the plate 14 is
adapted to enter. This pin is carried by a lever 14° pivoted to the plate 14 and
acted upon by a spring 14° as shown more clearly in Fig. 12, the arrangement being
such that by pressing the one end of the lever inward against the action of the said
spring, the pin 14 will be moved out of the hole 19 in which it was previously
held and the dial will be free to be rotated upon the spindle 5ª to any desired
extent, and upon releasing the said lever, the pin will be caused to enter the hole 1ª
next brought opposite to it and lock the dial and plate together. 14 is a spring
plate (Figs. 2 and 4) arranged to bear at its central part against the boss of the
worm wheel 13 and formed with three arms arranged to bear against the back of
the plate 14 so as to hold this plate and the dial 1 in close contact with each other
at all times and especially when the latter is unlocked from the former by moving
back the pin 14°.
Motion may be communicated from the leading screw to the worm 12 through
any suitable mechanism. In the example shown it is effected through the medium
of bevel wheels 19, 19ª carried by a frame 20 which is connected to the frame 16,
the connection between the leading screw and the driving wheel 19 being made by
means of a friction clutch (Figs. 7 and 8). This clutch in the arrangement shown
is tightened up by means of a nut wheel 21 having an internal flange 21ª that
bears against an external flange 22" on a female cone 22 which is tightened on to a
male cone 23 by turning the nut wheel in one direction on a screw thread flange 23*
on the said male cone, and freed by turning the nut wheel in the reverse direction.
The male cone 23 is connected to an internally screw threaded socket 24 which is
screwed on the end of the leading screw when the apparatus is fitted to a lathe.
22 is a milled wheel fixed on the female cone 22 by a lock nut 22° and by means
of which the arm 5 can be rotated by hand when the said cone 22 is freed from
the cone 23 and leading screw.
As will be obvious the clutch instead of being arranged between the leading
screw and the bevel wheels 19, 19, may, in some cases, be arranged between the
worm 12 and said bevel wheels, the wheel 19 in this case being connected direct to
the leading screw.
The indicating apparatus can be supported in any convenient position for use.
In the example shown in Fig. 1, it is carried by a rod 25 that can be fixed by a
screw 26 at any suitable height in a tubular holder 27 the lower end of which can
be readily secured to the floor by a bolt 28 (Figs. 13 and 14), the head of which
bears against the underside of the floor and the shank of which is provided with a
pin 29 journalled eccentrically in the boss of a handle 30 so that upon moving the

page_text: handle from the position shown in full lines to that shown in dotted lines, the foot
of the holder will be firmly clamped between the said boss and the floor. The
holder may of course be otherwise fixed to the floor if desired. Also the apparatus
may be carried by a bracket 31 adapted to be fixed to one of the legs or standards
of the lathe and carrying a rod 32 provided with a socket 33 in which the rod 25
carrying the indicator, can be fixed by the screw 26 at any suitable height as shown
in side and plan views in Figs. 15 and 16 respectively.
The dial is made in three concentric parts normally fixed together the inner or
central part being mounted upon the spindle 5", the middle concentric part carrying
the fingers 2 or equivalent part, while the outer concentric part is provided with
the indications representing lengths of travel of the saddle. By this method of
construction two or more such other parts may be provided each having differently
arranged fingers and indications so as to adapt the apparatus to leading screws
having different pitches.
The indicating apparatus is equally suitable for cutting either right or left-
handed threads.
The operation of the apparatus is as follows
a cut.
:―
Supposing upon a lathe having a leading screw of four threads per inch, it is
desired to cut a right-handed screw of five threads in three quarters of an inch,
that is ten threads in one and a half inches with the indicating apparatus as
described, the screw-cutting tool is first set square with the blank upon which the
screw is to be cut and the saddle then brought into the required position for starting
The nut is then placed in gear with the leading screw, and preferably a
suitable stop of wood is placed between the movable lathe headstock and the saddle
against which the latter may be run back to ensure the saddle occupying exactly
the same position each time it returns prior to commencing a fresh cut. The
apparatus hereinbefore described is then secured to the leading screw by means of
the screwed socket 24, Fig. 8, and adjusted to the proper height in its stand or
support by means of the rod 25 and set-screw 26.
As the assumed screw to be cut is ten threads in one and a half inches, the
fingers on the dial at 1, 3, 4, and 6 should be raised these fingers each indicating
one inch and a half travelled by the saddle when in gear with the leading screw.
The conical clutch 23 is then released by means of the hand-wheel 21, Fig. 8 so as
to leave the index or radial arm 5 (Fig. 1) free to be moved round on the dial by
hand, this movement being effected by turning the milled wheel 22, Fig. 8.
The
radial arm 5 is then moved until it comes in contact with one of the raised fingers
and the bell caused to sound and at this point the indicator must be again locked to
the leading screw by means of the clutch 23 and hand wheel 21. The lathe is then
set in motion and a cut taken along the blank. At the end of the cut the lathe is
allowed to continue running and the tool withdrawn by one hand and the half nut
lifted out of gear with the other. The saddle is then run back against the stop
previously mentioned, the tool adjusted for a deeper cut and the radial arm watched
until it touches the next finger in its travel around the dial whereupon the half nut
is lowered onto the leading screw with which it is caused to completely engage on
the stroke of the bell. The foregoing operations are repeated, without stopping
the lathe except to gauge the work, until the desired screw is cut. Stoppage of the
lathe is only necessary during the progress of the work when the threads in the
screw to be cut are not a multiple of the highest number of divisions on the dial in
use, for instance, when the dial is divided into six, as in the above example, and the
threads to be cut only run equal in five inches, such for instance as twenty six
threads in five inches. In this case the lathe would be stopped after passing the
number 5 on the dial by releasing the pin carried by the lever 14 Fig. 2, and
moving the dial backwards one division, until the index passes the number 6 when
the index would again measure each two and a half inches traversed by the saddle,
the fingers raised in this instance being at 2, 5 and 6. However when such a case
occurs it is advisable to divide the dial into 5 or 10 divisions to suit the threads per
inch upon the leading screw.

page_text: When a left-handed screw is to be cut, the index or radial arm 5 will be
rotated backwards or contra-clockwise upon the dial 1.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is —
1. Indicating apparatus for a screw cutting lathe in which an indicator operated
from the leading screw of the lathe is adapted to give an audible as well as a
visible indication of the proper times at which the engagement between the
leading screw and the feed nut can be made so as to ensure that the screw cutting
tool shall operate correctly.
2. Indicating apparatus for a screw cutting lathe, comprising a dial marked with
indications corresponding to definite length of travel of the saddle of the lathe and
provided with fingers or equivalent parts corresponding in position to said
indications, and adapted to be moved into operative and inoperative positions at
will, a bell, and a radial arm arranged to be driven through suitable mechanism
from the leading screw of the lathe and provided with means adapted to be
operated by contact with one or other of the said fingers for sounding the said
bell at the required times substantially as herein described for the purpose
specified.
3. Apparatus of the kind referred to in the preceding claim, in which the dial is
made adjustable about its axis independently of the driving gear substantially as
described for the purpose specified.
4. Indicating apparatus for a screw cutting lathe, constructed and operating
substantially as described and shown.
בד
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1
1000
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.