Improvements in Screw Cutting Lathe.
Year: 1885

page_text: Improvements in Screw Cutting Lathe.
JAMES SHAW, THORNTON HARRISON and WILLIAM SHAW, Engineers 50
Lyndhurst Street Leeds Road, Bradford, do hereby declare the nature of our
invention for IMPROVEMENTS IN SCREW CUTTING LATHE, FOR CUTTING POSITIVE
GAINING SCREWS, to be as follows:-
To the end of the lathe gauntree is fixed an other gauntree in an upright position,
and made so as to be movable to any degree required. The screw of ordinary lathe
working the screw of the upright gauntree, and so moving the saddles of both
gauntrees up and down as required, the saddles being made fast to each other by
means of a connecting rod.
JAMES SHAW.
THORNTON HARRISON.
WILLIAM SHAW.
We JAMES SHAW, THORNTON HARRISON, and WILLIAM SHAW, all of 50
Lyndhurst Street Leeds Road, Bradford in the County of York Engineer do
hereby declare the nature of our invention for IMPROVEMENTS IN SCREW-CUTTING
LATHE and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:—
This invention relates to an improved appliance for traversing the lathe saddle
for the purpose of cutting differential screw-threads, such threads regularly
increasing or decreasing their pitch.

page_text: To carry out our invention we fit a supplementary gantre at the end of the lathe
gantry, at any convenient angle therewith and traverse the lathe saddle by means
of a connecting rod, or rods, from a saddle on such supplementary gantre, which is
traversed by gearing connected with the lathe mandrel; thereby communicating to
the lathe saddle a speed of traverse, which relative to the speed of the mandrel,
increases or decreases.
Reference is to be had to the accompanying drawings forming part of this
specification in which similar letters of reference indicate corresponding parts in
both of the figures. Figure 1 is an elevation of a screw-cutting lathe shewing the
application of our improvements. Figure 2 is a plan of the same.
A supplementary gantre A is hinged to the end of the lathe gantre B by the
brackets C and D, it may be fixed at any angle therewith and is supported by the
quadrant bracket E; the stud F on the supplementary gantre A being secured by
the nut G in the slot H. The saddle J is traversed by the screw K actuated
by the leading screw L, which for this purpose is disconnected with the lathe
saddle M and is merely used for transmitting motion from the lathe mandril N to
the screw K. A bevel wheel O is therefore mounted at the end of it, which com-
municates motion to the bevil wheel P on the screw K. by means of the intermediate
wheels Q, R, S and T which arrangement allows the angle formed by the supple-
mentary gantre and the lathe gantre to be altered without severing the connection
of the screw K and the leading screw L.
The saddle J as an uniform traverse imparted to it from the lathe mandrel N
and being connected by the telescopic connecting rod U to the saddle M it transmits
a traverse thereto, the speed of which relative to the speed of the saddle J regularly
decreases when sliding forward, towards the mandril, and regularly decreases when
sliding backwards.
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 lathes for cutting differential screw threads, the means, or method of
traversing the lathe saddle substantially as herein shewn and for the purpose
set forth.