IMPROVEMENTS IN SCREW CUTTING LATHE FOR CUTTING SCREWS WITH AN INCREASING PITCH
Year: 1886

page_text: JAMES SHAW, THORNTON HARRISON and WILLIAM SHAW all of 50 Lyndhurst
Street Bradford Yorks Engineers do hereby declare the nature of our invention
for IMPROVEMENTS IN SCREW CUTTING LATHE FOR CUTTING SCREWS WITH AN
INCREASING PITCH to be as follows:-
Consists of driving the saddle of lathe, by means of a fork runing (or moving)
in the groves of a screw having a thread with an increasing pitch-(which screw
takes the place of the ordinary screw in front of lathe) and at the same time
regulating the cutter to the angle required in cutting screws of an increasing
pitch.
JAMES SHAW.
THORNTON HARRISON.
WILLIAM SHAW.

page_text: an Increasing Pitch.
We JAMES SHAW, THORNTON HARRISON, and WILLIAM SHAW, of 50 Lyndhurst
Street, Bradford, in the County of York, Engineers, do hereby declare the nature
of this invention for IMPROVEMENTS IN SCREW-CUTTING LATHE FOR CUTTING
SCREWS WITH AN INCREASING PITCH, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
יך
2
WC7
cutter
This invention relates to novel and useful improvements in lathes for cutting
screws of increasing pitch; and its object to impart an increasing or decreasing
traverse to the saddle of the lathe, and also to automatically regulate the angle of
relief of the cutter or tool, that is the angle formed by the face or faces of the c
or tool and the work operated upon.
"For this purpose we employ a leading screw of increasing pitch to impart the
requisite motion to the lathe saddle, the said screw being preferably cut by the
apparatus described in the Specifications of Letters Patents granted to us on
the 6th day of January 1885, and numbered 175 and 186.
The cutter or tool is secured on a horizontal spindle mounted in the tool box, the
axis of the said spindle lying approximately in the same horizontal plane as that
of the leading screw. The outer end of the said spindle is of rectangular or other
suitable section adapted to slide into a corresponding hole formed in a socket filted
in a bracket sliding on the leading screw, and secured to the lathe saddle. The
said socket has a forked end which engages with the groove of the leading screw,
thereby traversing the lathe, and also altering the angle of the tool or cutter
secured to the said spindle in a corresponding degree to the variation of the angle
of the thread in the leading screw.
Reference is to be had to the accompanying drawing forming a part of this
specification in which similar letters of reference indicate corresponding parts in all
the figures.
Figure 1 is a longitudinal elevation of a lathe fitted with our improvements.
Figure 2 is a plan of the same. Figure 3 is a transverse vertical section of the
bracket secured to the saddle and sliding on the leading screw, and Figure 4 is a
perspective view of the said forked socket and the end of the spindle sliding
therein.
The leading screw of increasing pitch A is mounted in brackets B secured to the
bed of the lathe, and instead of being directly connected to the lathe mandril, the
requisite motion is preferably communicated to such screw from a parallel shaft O,
occupying the position of the leading screw in an ordinary lathe, and driven in a
similar manner. Motion is conveyed to the screw A from the shaft C by the
intermediate wheel D, which engages with the wheel E on the said shaft, and the
wheel F on the screw.
The cutter G is secured to the inner end of the spindle H mounted in the tool
box J, which is preferably provided with conical bearings. The outer end K of
the spindle H is of rectangular section, and slides in a corresponding hole formed

page_text: in the end of the forked socket L, which socket is enclosed in the slide bracket M
fixed to the saddle P, and the projections N on the end of the fork are thereby
retained in the thread of the screw A. The sliding or telescopic connection between
the forked socket L and the spindle H allows the tool box to be transversely
adjusted by means of the slide O in the saddle P.
When the lathe is in operation, the fork L engaging with the screw A com-
municates a traverse of varying speed to the saddle P, by means of the bracket M,
and also imparts a slight rotary motion to the spindle H corresponding to the
variation of the angle of the screw thread, thereby automatically altering the
angle of relief of the cutter G.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare what
we claim is
In a lathe for cutting screws of increasing pitch, the construction and arrange-
ment of mechanism for traversing the saddle at a varying speed and simultaneously
regulating the angle of the cutter, substantially as herein shown and described.
DRACUP & NOWELL,
Bradford, Agents.