Improvements in Screw Cutting Machinery.
Year: 1892

page_text: Date of Application, 12th Feb., 1882
Complete Specification Left. 11th Nov., 1892-Accepted, 17th Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in Screw Cutting Machinery.
I, JAMES YATE JOHNSON of 47 Lincoln's Inn Fields, in the County of
Middlesex Gentleman do hereby declare the nature of this invention (which has
been communicated to me from abroad by Edmondo Dubosc of Turin in the
Kingdom of Italy, Engineer) to be as follows:-
This invention relates to a screw cutting machine working with a rocking motion
and in which the screw cutting is performed by means of dies or grips capable of
radial adjustment and which open automatically at the end of the operation in order
to admit of the removal of the bolt or screw.
Rotary motion is imparted to the dies and the screw blank being held fast in jaws
carried by a moveable slide is moved longitudinally by the action of the dies.
The latter open when the screw is to be removed and close or move towards one
another with precision into the position corresponding to the diameter of the screw
that is to be cut without requiring the motion of the machine to be either stopped
or reversed.
This result is obtained without the intervention of springs by means of a rocking
motion mechanism.
The machine is provided with a hollow mandril connected or formed in one with
a circular die plate or disc presenting three or other suitable number of radial
grooves or slots forming guides for the screw cutting dies. Two other discs or
plates are arranged on opposite sides of this die plate being retained in position
laterally but being capable of rotating freely upon the mandril.
The front plate is provided with excentric ribs which engage with corresponding
notches or recesses in the radially sliding dies and have the effect of causing the
said dies to simultaneously approach or recede from the centre when this plate
rotates relatively to the intermediate plate or disc carrying the dies.
The two plates on the opposite sides of the intermediate or die plate are provided
with circular bevelled racks and the intermediate plate carries one or more corre-
sponding cone or bevel pinions mounted loosely upon studs and gearing with both of
the aforesaid racks.
In order to open or separate the dies it is simply necessary to rotate the front
plate relatively to the die plate in the same direction that is to say both plates being
rotated in the same direction it is necessary to cause the front or ribbed plate to
gain upon the die plate. This effect is produced by stopping or retarding the
rotation of the back plate. When this is done the cycloidal movement of the
pinion causes the front plate to acquire an angular motion double that of the die
plate and when one sixth of a revolution has been described the dies are opened or
separated to the maximum extent by the action of the excentric ribs on the said
front plate.
An adjustable bolt can be fixed in any part of the die plate and comes in contact
with a stop or projection formed upon the ribbed plate. By adjusting the position
of this bolt the degree of opening of the dies or the standard diameter of the screw
to be cut can be regulated and as the die plate propels the ribbed 'plate by means
of this bolt this diameter remains constant so long as the two plates rotate as one
piece.
A brake acts upon the ribbed plate and another brake acts upon the back plate.
A slight pressure exerted by the former brake has the effect of bringing the
adjustable bolt into contact with the stop and thus maintains constant the amount
of separation of the dies notwithstanding the vibration resulting from the working;

page_text: the die plate and front or ribbed plate then rotate as one piece and the back plate
follows them or partakes of the same motion.
Now if the front brake be released and at the same time the back brake be
tightened on the back plate the latter stops and the dies open as hereinbefore
explained...
When the screw is being cut the brakė is tightened on the front plate or disc and
the brake acting on the back plate is loosened. When the screw cutting is finished
the front brake is loosened and the back brake is tightened.
This effect is produced by means of a weight arranged in front of the machine
within reach of the operator and working upon rollers so as to travel readily upon
a pivoted or rocking beam or lever. When the weight is placed at one end of the
beam the front brake is loosened and the back brake tightened. By simply shifting
the weight by hand from one end of the lever to the other the dies are thus enabled
to be opened or closed without stopping or reversing the motion of the mandril.
The weight may be displaced or shifted automatically. With this object a rod
is provided at a suitable distance apart with rings or collars arranged on opposite
sides of a sliding ring moving with the slide carrying the bolts or blanks. The
displacement of this rod by the movement of the said slide rocks the support of the
beam in such a manner as to set the latter at an angle which causes the weight to
travel over to the opposite or lowest end of the beam and produce the desired effect
upon the brakes.
Any suitable combination of cams and levers or other mechanism may be.
employed to transmit the action of the weight to the two brakes simultaneously.
This screw cutting machine with rocking motion as hereinbefore described
presents the advantages resulting from the exclusion of springs in its construction it
also presents a special peculiarity which ensures accuracy in the performance of the
work and protects the dies from breakage.
When the forged or turned bar or blank in which the screw is to be cut is properly
prepared in accordance with the diameter of the screw the latter may be cut in one
operation and if the index attached to the adjustable bolt remains opposite the zero
mark on the plate this indicates that the screw cut is of exactly the right diameter
but if there be an excess of metal to be removed that is to say if the blank be too
thick the index will move over the divisions on the plate and this indicates that the
diameter of the screw is greater than it should be and that the blank must be passed
through the dies again or until it is reduced to the proper size which is indicated by
the index remaining in one position.
This screw cutting machine is consequently self compensating in its action and
automatically corrects any errors that may have been made in the diameter of the
blank.
The power of the brakes can be easily regulated either by limiting the travel or
leverage of the weight on the beam by means of adjustable collars or by partially
neutralising its action by means of supplementary weights.
> Dated this 12th day of February 1892.
J. H. JOHNSON & Co.,
Agenta.
!.!
COMPLETE SPECIFICATION.
Improvements in Sorew Outting Machinery.
, JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this invention which has been com-
municated to me from abroad by Edmondo Dubosc of Turin in the Kingdom of 50
Italy Engineer 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 screw cutting machinery in which the screw is cut by.
dies or grips which are capable of "radial" adjustment and are caused to open

page_text: automatically at the end of the operation by the action of a rocking lever in
order to admit of the removal of the threaded bolt or screw as hereinafter
described.
Rotary motion is imparted to the dies and the screw blank is fixed in jaws
carried by a slide or carriage moved longitudinally by the action of the dies which
are arranged to close or move towards one another into the precise position
corresponding to the diameter of the screw that is to be produced without requiring
the motion of the machinery to be either stopped or reversed for the purpose of
adjustment.
This result is obtained without the intervention of springs by means of the
lever with a rocking motion hereinbefore referred to and which suggested the
name "rocking motion screw cutter by which my foreign correspondent
designates the machines constructed according to this invention.
"
And in order that this invention may be fully understood I shall now proceed
more particularly to describe the same and for that purpose shall refer to the
several figures on the annexed sheet of drawings the same numerals of reference
indicating corresponding parts in all the figures.
Figure 1 of the accompanying drawings represents in longitudinal section the
working parts of an example of a screw cutting machine constructed according to
this invention.
Figure 2 represents in front elevation an intermediate disc carrying cone pinions
forming part of the said machine as hereinafter explained.
Figure 3 represents the machine in end elevation partly in section on the
line A B C. D Figure 4.
Figure 4 drawn to a smaller scale represents the machine in elevation.
This machine is provided with a hollow mandril driven by gearing 1ª
(Figure 4) connected or formed in one piece with a circular die plate or disc 2
provided with a head or boss 2ª presenting (in the example illustrated) three
radial grooves or slots 3 forming guides for three screw cutting tools or dies 4.
Two other discs or plates 5 and 6 are arranged on opposite sides of the die plate 2
and are retained in position laterally but are capable of rotating independently of
the mandril 1 and die plate 2. The front plate 5 is provided with three excentric
ribs 7 (Figures 1 & 3) which engage with corresponding notches or recesses in
the radially sliding dies and have the effect of causing the said dies to simul-
taneously approach or recede from the centre when this plate 5 rotates relatively
to the intermediate plate or disc 2 in which the dies 4 are supported. The two
plates 5 and 6 on the opposite sides of the intermediate plate 2 are provided with
circular bevelled racks 8 and 9 (Figure 1) and the intermediate plate 2 carries
cone or bevel pinions 10 (three of such pinions being provided in the example
illustrated in Figures 1 and 2) mounted loosely upon studs and gearing with the
rack 8 on one side and on the other side with the rack 9.
In order to open or separate the dies it is simply necessary to rotate the plate 5
relatively to the die plate 2 in the direction of the arrow (Figure 3). The plate 2
being itself caused to rotate in this direction in cutting the screw it is necessary to
cause the ribbed front plate 5 to gain upon it. This effect is produced by stopping
or retarding the rotation of the back plate 6. When this plate is stationary for
example the cycloidal movement of the pinions 10 (each point in the cone of the
pinion describes a cylindrical cycloid) causes the front plate 5 to acquire an
angular motion double that of the plate 2 and when one sixth of a revolution has
thus been described the dies 4 are opened or separated to the maximum extent by
the action of the excentric ribs 7.
An adjustable bolt 11 (Fig. 1) can be fixed in any part of a circular undercut
groove in the die plate 2 and comes in contact with a stop or projection formed
upon the ribbed plate 5. By adjusting the position of this bolt the degree of
opening of the dies or the standard diameter of the screw to be cut can be
regulated and as the die plate 2 propels the ribbed plate 5 by means of the bolt 11

page_text: this diameter remains constant so long as the plate 5 does not gain upon the
plate 2.
A pair of brake blocks 12 acts upon the periphery of the plate 5 (Figure 3)
and another pair of brake blocks 13 (Figures 1 and 4) acts upon the plate 6. A
slight pressure exerted by the brake 12 has the effect of bringing the bolt 11 into
contact with the stop on the plate 5 and thus maintains constant the amount of
separation of the dies notwithstanding the vibration resulting from the working.
Under these conditions the plates 2, 5 and 6 rotate at the same rate or as one
piece.
Now if the brake 12 be released and at the same time the brake 13 be tightened
on the plate 6 the latter is retarded or stops and the dies 4 are opened as herein-
before explained. When the screw is being cut the brakes 12 are tightened on the
front plate 5 and the brakes 13 are loosened. When the screw cutting is finished
the brakes 12 are loosened and the brakes 13 are tightened in order to open the
dies.
These operations are performed by means of a weight 14 arranged in front of
the machine within reach of the operator and capable of rolling or travelling
readily from one end to another of a rocking beam or lever 15, 16 (Fig. 4)
oscillating upon a rock shaft 24. The said weight 14 is in the form of a disc or
cylinder provided with an annular peripheral groove (Figure 3) rolling in a frame
or guide formed by the lever 15 16 and may be conveniently made in two parts
forming a box and a cover connected together by 3 screws the said box being filled
with lead. When the weight 14 is placed at the end 15 of the rocking beam or
lever 15, 16 the brake 12 is loosened and the brake 13 tightened thereby opening the
dies. By simply shifting the weight 14 by hand from one end of the lever to the
other the dies can be immediately opened or closed without stopping or reversing
the movement of the mandril. To cause the weight 14 to be displaced or shifted
automatically a rod 17 (Figure 4) may be employed being provided with rings or
collars 18, 19 arranged at a suitable distance apart upon opposite sides of a sliding
ring 20 moving with the slide 31 carrying the bolts or screw blanks. The displace-
ment of this rod by the movement of the said slide or carrier rocks the support 21
of the lever 15, 16 in such a manner as to set the latter at an angle which causes
the weight 14 to roll or travel over to the opposite end of the lever from 15 to 16
or from 16 to 15 and operate the brakes 12 and 13 so as to open or close the dies.
It is evident that any suitable combination of cams and levers or other mechanism
may be employed to transmit the action of the weight 14 to the two brakes 12 and 13
simultaneously.
A convenient arrangement of links and levers is represented in the annexed
drawing but any other equivalent kinematic combination capable of producing the
same effect may be employed if preferred.
The position of the blank is indicated in dotted lines at 30 Figure 4 the said
blank being represented as being held in an adjustable holder or carriage 31.
The screw cutting machine with rocking motion as hereinbefore described is
devoid of complication and presents advantages resulting from the exclusion of
springs in its construction; it also presents a special peculiarity of considerable
importance in practice and which results from the fact that the rocking motion
hereinbefore described constitutes a safety apparatus which ensures accurate work
and protects the dies from breakage.
When the forged or turned bar or blank in which the screw is to be cut is
properly prepared in accordance with the diameter of the screw the thread may be
cut in one operation and if the index which may be provided on the bolt 11 remains
opposite the zero mark on a scale provided on the plate 5 this indicates that the
screw cut is of exactly the right diameter but if there be an excess of metal to be
removed that is to say if the rod or blank be too thick relatively to the diameter
of the finished screw (an excess of a few tenths of a millimetre is enough to break
the dies in ordinary machines) the index will move over the divisions on the plate 5

page_text: (each division representing a movement of the dies corresponding to one tenth of a
millimeter) which indicates that the diameter of the screw is 1, 2 or 3 tenths of a
millimeter for example greater than it should be, and that the blank must be passed
through the dies again until it is reduced to the proper size which is indicated by
the index on the bolt 11 occupying the same position after the pass as it did at the
commencement.
This screw cutting machine is consequently self compensating in its action and
automatically corrects any errors that may have been made in the diameter of the
blank. Breakage of the dies is likewise obviated and when the blanks are not of
the correct size the workman is compelled to pass them two or more times through
the dies in order to do the work which could have been done in one passage if the
blank had been properly prepared. The action is the same when a deep thread
has to be cut on a large blank or when the metal is extra tough or is liable to break
away or is deficient in homogeneity. Moreover the power of the brakes can be
easily regulated either by limiting the travel or leverage of the weight 14 on the
lever or rocker 15, 16 by means of adjustable stops or by partially neutralising its
action by means of supplementary weights suspended from hooks 22, 23 (Figure 1).
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
1. A screw cutting machine in which the screw cutting dies are moved towards
or from one another by means of excentric ribs engaging with the said dies and
controlled by a brake mechanism which is worked by hand or is automatically
brought into action by the slide carrying the bolt or blank acting upon a rocking
beam or lever all substantially as hereinbefore described and illustrated in the
accompanying drawings.
2. The combinations and arrangements of parts constituting the improvements
in screw cutting machinery substantially as hereinbefore described and illustrated
in the accompanying drawings.
Dated this 11th day of November 1892.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, Agents.