IMPROVEMENTS IN SCREW- CUTTING MACHINES
Year: 1883

page_text: LETTERS PATENT to Alexander Melville Clark of the firm of A. M. and
W Clark of 53 Chancery Lane in the County of Middlesex Fellow of the
Institute of Patent Agents for an Invention of IMPROVEMENTS IN SCREW-
CUTTING MACHINES Communicated to him from abroad by Louis Ernest
Lepine of Paris, France
COMPLETE SPECIFICATION filed by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 14th April 1883.
ALEXANDER MELVILLE CLARK of the firm of A. M. and W. Clark of 53 Chancery
Lane in the County of Middlesex, Fellow of the Institute of Patent Agents.
IMPROVEMENTS IN SCREW-CUTTING MACHINES Communicated to me from abroad
by Louis Ernest Lepine of Paris, France
This Invention relates to a universal screw cutting machine tool for cutting
right or left hand screwthreads of any desired pitch upon rods, the pitch being
capable of the most minute variation.
The principle of the apparatus consists in making the rate of motion of the
ordinary slide rest of a lathe to depend upon the degree of obliquity in a horizontal
plane given to a leading or guiding bar fixed upon a slide mounted to slide in
ways beneath the slide rest in a direction perpendicular to the motion of the slide
As the angle and direction at which the leading or guiding bar is placed
can be infinitely varied, the rate of motion of the slide rest and consequently the
pitch of the screwthread may also be varied indefinitely.
rest.
In order that the Invention may be more readily understood, I will proceed to
describe the screw cutting machine-tool with reference to the accompanying
drawings in which Figure 1 is a plan, and Figure 2 a vertical section of the tool
taken on line 1. 2. 3. 4. 5. 6 Figure 1. Figure 3 is a plan and end view of the
slide carrying the leading bar, and Figure 4 is a plan and edge view of the bar
whose inclination to the longitudinal axis of the slide can be adjusted as desired.
Figure 5 shows elevations and plan of a clamp which embraces the leading bar and
is pivoted to the slide rest so as to adapt itself to the inclination of the bar, and

page_text: whereby motion is transmitted to the slide rest according to the degree or
inclination of the said bar. The same letters of reference indicate like parts in all
the figures.
8
The improved universal screw cutting tool is mounted upon a cast iron frame a
provided with a fixed head stock b carrying a hollow mandrel & screwthreaded at ƒ {
to receive the driver chuck g, all as in an ordinary lathe. Upon the other end of
the mandrel is a pinion h fast with a hand wheel i j for driving tool. b¹ is the
poppet head and the back centre. is a slide rest moving on ways c c on the
lathe bed. The pinion h gears with a wheel m fast on a shaft n at the middle of
9.
which is a pinion o which gears with a rack p on the underside of the slide
This slide moves in ways rr on frame a in a direction perpendicular to the axis
of the lathe, and upon it is fixed the leading bar 8 whose greater or less inclination
to the right or left determines the pitch and direction of the screw thread. The
bar & is embraced by a pivoted clamp t whose pivot u turns freely in slide rest l.
The slide q moves forwards or backwards in its ways according to the direction of
rotation of wheel m, the motion being transmitted to the slide q by means of
wheel m, pinion o, and rack p. The slide q, which with guide bar 8 constitutes in
combination with clamp t and pivot u the essential features of the apparatus, is
It has transverse slots vv near each end to
represented separately in Figure 3.
receive the binding studs which pass through the ends of the bar s, and by which
the said bar is fixed in the desired position: One end of said bar has a slot x
through which the one screw stud y passes to admit of the bar s being readily
fixed more or less diagonally either to the right or left. The bar s being engaged
in the pivoted fork or clamp t, the slide rest is thereby caused to move to the
right or left, and as the angle of the guide bar may be infinitely varied, the rate of
motion of the slide rest and consequently the pitch of the screwthread may be
This cannot be done even with the best and
varied to any extent howover small.
most expensive screw cutting lathes. A pointer parallel with the axis of the
leading bar s is fixed on the upper end of pivot u and works over a horizontal
quadrant w fixed on the slide rest to facilitate the adjustment of the bar 8, the
graduations of the quadrant corresponding to the different degrees of pitch for the
screwthreads which will be right or left handed according as the pointer is set to
the right or left.
This machine tool may be driven either by hand or by power, as will be readily
understood.
With this apparatus the pitch of a screw can be readily and accurately ascer-
tained, it being simply necessary to mount the screw between the centres of the
lathe, to loosen one end of the bars to put the pointer at zero, and to replace the
cutting tool by a small wheel which is engaged in the screwthread. When the
apparatus is set in motion the pointer and guide bar will assume an inclination
corresponding to the pitch of the screw which will be accurately indicated by the
graduation on the dial over which the pointer stops. As in the case of screws of
fine pitch, the motion of the slide rest is very small, and therefore but a short
length of screwthread can be cut at one passage of the guide bar by shifting said
guide bar to a fresh position and refixing it at the same angle the cutting of the
screw may be continued uninterruptedly at the same pitch. This shifting of the
guide bar may also be effected automatically instead of by hand, and I may employ
any convenient mechanical arrangement for effecting it.
Having described the nature of the said Invention and the manner of performin
the same, I declare that what I claim as new and desire to secure by Letter
Patent is.
In a screw cutting lathe or machine for cutting or tapping screwthreads
1 The employment in combination with the slide rest or tool holder of
leading or guide bar receiving reciprocating motion in a direction perpendicular
the motion of the slide rest and adjustable at different angles to the direction of it
motion for moving the slide rest at different speeds, substantially in the mann
shown and described.

page_text: 2nd In combination with an adjustably inclined leading bar arranged and
operating as described, the pivoted clamp or fork tu for engaging the slide rest
with the leading bar and imparting motion to the slide rest, substantially as shown
and described.
3rd The combination of the adjustably inclined leading bar arranged and
operating as described, the pivoted clamp engaging the slide rest therewith, the
index fixed on the pivot, and the quadrant fixed on the slide rest, substantially as
shown and described for the purpose specified.
4th The combination of the adjustable leading bar, the sliding table, and the
slots and means of fixing the bar thereon at any desired inclination to the direction
of its motion, substantially as shown and described.
5th The combination of the adjustably inclined leading bar and its supporting
slide arranged to work in the manner described, the pivoted clamp connecting the
slide rest therewith, and gearing for imparting rectilinear motion to the slide
proportional to the rotary motion of the mandrel, substantially as shown and
described.
In Witness whereof I the said Alexander Melville Clark have hereunto set
my hand and seal this fourteenth day of April, A.D. 1883.