Improvements in Screw Cutting Lathes.
Year: 1891

page_text: Date of Application, 12th Sept., 1891
Complete Specification Left, 11th June, 1892-4ccepted, 30th July, 1892
PROVISIONAL SPECIFICATION.
Improvements in Screw Cutting Lathes.
CHARLES WILLIAM HARRY PENWARDEN of 46 Conway Road Plumstead
Road Plumstead, in the County of London Engineer do hereby declare the nature
of this invention to be as follows:-
―
My present invention has reference to all screw cutting lathes, with the object
of abolishing the practice of marking wheels when screw cutting.
It consists necessarily of a worm wheel, revolving freely on a spindle, this spindle
being carried by the saddle of the lathe, the worm wheel gearing with the leading
screw. In the worm wheel are drilled small holes at equal distances apart, on
circles of varying diameter, a pin fitting these holes accurately. On the larger
portion of the pin, is a thread or screw, which rotates in a cylindrical box, producing
motion backward and forward, the rotary motion of the pin, is communicated from
the handle, by two toothed wheels, one wheel being securely keyed to the pin, and
the other to the spindle working the nut in and out of gear. The cylindrical box
may be easily adjusted to suit the holes in the worm wheel, by simply moving it in
a circular slot, made in the saddle of the lathe.
The chief feature of this invention, is that the half nut usually used when screw
cutting, is restrained from gearing with the leading screw by a pin, which is able
to go in and out of gear with, the worm wheel at certain intervals; and as these
intervals correspond to a whole number of threads on the part under operation, the
tool necessarily will coincide with the thread each time the pin enters one of the
holes, or in other words the mandril. makes a complete number of revolutions while
the worm wheel advances one hole; it can easily be seen that each time the pin
enters a hole, the nut immediately gears with the leading screw, and the mandril
having made a complete number of revolutions, it is practically in the same position
as when the pin geared or entered the last hole, so motion given to the saddle,
and the tool each time a fresh cut is taken will be found to coincide with the thread
previously cut, so that the nut does the work of moving the saddle, while the worm
wheel acts as a guide to prevent the movement of the handle and half nut, till
such time as the part under operation and the leading screw are in their correct
relative positions.
.
The worm wheel may act as both guide and nut combined if desired, for by
entering the pin in one of the holes it will immediately have the effect of stopping
the rotation of the worn wheel; thus the worm wheel forms a nut with the leading
screw and produces the required longitudinal motion of the saddle.
Dated this 10th day of Sentember 1891. ··
COMPLETE SPECIFICATION:
Improvements in Screw Cutting Lathes.
CHARLES WILLIAM HARRY PENWARDEN of 46 Conway Road Plumstead
in the County of London, Engineer, 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 present invention has reference to all screw cutting lathes for the object of

page_text: abolishing the practice of marking wheels when screw cutting; it is intended more
particularly for use with small lathes, & for cutting fine pitches, though it may be
adapted to suit all kinds of lathes & for cutting all pitches.
Referring to Figs. 1 & 2 it will be seen that it consists of a worm wheel (A)
gearing directly into the leading screw (S) the worm wheel (A) being securely
fixed to a spindle (B) this spindle (B) is carried by a small bracket (E) which is fixed
to the saddle (V) of the lathe as shown by the two screws (C), (C) the spindle (B)
is also able to revolve freely in the bracket (E) this bracket (E) acting simply as a
support for the spindle (B), to the other end of this spindle (B) is securely fixed a
disc (G) with holes drilled in the face of it at equal distances apart on a circle
concentric with the centre of the disc (G) 'the wingnut (W) being simply' for
keeping the disc (G) in its place the two small brackets attached to the bracket (e)
by means of the screws (C), (C); and shown at (H), (H) act as a support for the
leading screw.
Referring now to the half nut (K), it will be seen to derive its motion by the
movement of the handle (M) the slot (N) in the quadrant (T) being so cut as to
lift the nut wholly out of gear by means of the pin (Q) which is screwed into the
half nut (K) the other end works freely in the slot N.
Referring to Fig. 3, will be seen a section through the pin (P), the hole is
bored in the bracket (E) & screwed one end as shown at (R), the other end (R)
being bored the same size as the bottom of the thread so as to be a support to the
pin (P) the quadrant & handle as shown at (M.) & (T) are in one piece, the motion
of the handle (M) in a downward direction produces both the motion of the half
nut in a downward direction & also the advancement of the pin, P, which enters the
holes in the disc (G) the slot is so made that the pin (P) enters into gear with the
disc (G) before the nut begins to move downwards.
}
In the arrangement I have used a lathe the leading screw having 4 threads
per inch & the worm wheel 32 teeth, with this combination you can cut all pitches
which come a whole number in eight inches. I propose using a set of discs with a
different number of either holes notches or teeth in each, so as to cut 'threads whose
pitches do not come whole numbers in one inch; with the plate of 8 holes all
threads advancing from four by one to the inch such as 4, 5, 6, 7 etc. can be cut by
this combination; with threads of a greater pitch the arrangement is not necessary
the lathe as a rule travelling slow enough to be able to catch the wheels, but the
arrangement can be adapted also for cutting these threads.
I also wish to adopt gearing, where necessary, for cutting very aineven pitches,
for instance-
In the combination explained above when the 'worm wheel moves through one
eighth of a revolution, the saddle of the lathe will move, through one inch, if the
worm wheel moves through one revolution the saddle will move through 8 inches
so that by this combination you can cut up any thread which comes to a whole
number in 8 inches. If instead of driving the disc direct from the worm wheel I allow
it to run loose on a spindle and let it derive its rotation from two toothed wheels
suitably geared with the worm spindle and disc it will easily be seen by making
these twheels in size as:2 is to one that the disc will make one revolution to two of
the worm wheel; so when the disc makes one revolution the saddle will travel
16 inches that is to say by this combination you can cut up any threads which
comes a whole number in 16 inches; thus it is possible, to alter the gearing to suit
any particular class of work the lathe is used for, & to cut all threads, of course
instead of these two wheels being used could increase the size of the worm wheel
which would produce the same effect but as the wheel would become rather large it
would not be very convenient.
Thus it will clearly be seen that the disc with either the holes notches or teeth
acts simply as a guide to prevent the motion of the half, nut; and the worm wheel
is simply for communicating the regular rotary motion of the leading screw to

page_text: Having now particularly described & ascertained the nature of my said
invention & in what manner the same is to be performed I declare that what I
claim is:-
(1.) Arranging the worm wheel, disc, pin & half nut in conjunction with one
another in the manner herein above described for the purpose set forth.
(2.) Using a worm wheel to communicate the motion of the leading screw to
the disc.
(3.) Using a disc as a receiver of this motion to act as a guide for the motion of
the nut as above described.
(4.) That the intervals on the disc, which correspond to a whole number of
threads on the part under operation may be produced either by teeth, notches or
holes.
(5.) Also the arrangement of wheels for cutting any threads in the manner herein
above described for the purpose set forth.
10th June 1800
CHAS. W. H. PENWARDEN.