AN IMPROVED CONSTRUCTION OF SCREW STOCK
Year: 1878

page_text: LETTERS PATENT to Percival Everitt, of Great Ryburgh, in the County of
Suffolk, Engineer, for the Invention of "AN IMPROVED CONSTRUCTION OF
SCREW STOCK."
Sealed the 16th April 1878, and dated the 5th February 1878.
PROVISIONAL SPECIFICATION left by the said Percival Everitt at the Office
of the Commissioners of Patents on the 5th February 1878.
PERCIVAL EVERITT, of Great Ryburgh, in the County of Norfolk, Engineer.
"AN IMPROVED CONSTRUCTION OF SCREW STOCK."
The object of this Invention is to provide for feeding up the cutting dies of
screw stocks to their work without stopping the screw cutting operation, and also
to facilitate the release of the work and the changing of the dies in the stock.
The Invention applies chiefly to that class of screw stocks in which a stationary
and a movable die are used, and which is operated by a pair of handles. Upon
the side of this stock a cam is pivotted slightly out of line with the centre of the
stock for advancing the sliding die to its work. This cam terminates in a handle,
which serves to give it an axial motion. The sliding die bears upon the periphery
of this cam, and under its action is advanced towards the stationary die as its
increasing radius is brought. round into line therewith.
The form of this cam will be such that when its smallest radius is in line with
the cutting die the removal of the die from the stock may be readily effected, and
when its largest radius is in line with the dies (the moving die having completed
its advance) it will serve as a gauge for determining the exact diameter required
for the screw.
When the dies are set up to the work, the operator can, by a slight continuous
pressure on the handle of the cam, feed the movable die forward until the handle
of the cam comes into line with the handle of the stock. At this time the largest

page_text: radius of the cam will be brought into action, and the attendant will thus know
without inspection that the screw thread is brought to the required gauge.
By simply throwing back the handle of the cam pressure is taken off the dies,
and the work may be instantly released.
By the use of this arrangement of screw stock it will be readily understood that
the operation of screw cutting may be greatly expedited.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Percival Everitt in the Great Seal Patent Office on the 2nd August
1878.
PERCIVAL EVERITT, of Great Ryburgh, in the County of Suffolk, Engineer.
"AN IMPROVED CONSTRUCTION OF SCREW STOCK."
The object of this Invention is to provide for feeding up the dies or other cutting
tools of screw stocks to their work without stopping the screw cutting operation,
and also to facilitate the release of the work and the changing of the dies in the
work.
The Invention applies chiefly to that class of screw stocks in which a stationary
die and a moveable die or screw cutting tool are used, and which is operated by a
pair of handles.
In the accompanying Drawing I have shewn my improved screw stock in several
positions the better to explain its action.
Fig. 1 shews the screw stock in side view, and in the position which the move-
able parts take when the limit of advance is reached by the sliding die; Fig. 2 is
a section taken in the line 1, 2, of Fig. 1, shewing the dies in their closest position;
Fig. 3 is a side view of the screw stock shewing the position of the acting parts
when the cutting of the screw is commenced; and Fig. 4 is a view of the screw
stock shewing the position given to the feeding and gripping cam when it is
required to insert or remove the cutting dies.
In these views A is the screw stock furnished with a pair of handles A* as
usual. The stock is made with a rectangular slot to receive the threading dies a, a¹,
which are held in place by vertical guides formed on the sides of the slot as usual.
The die a is bedded in the stock, and the die a¹ is free to slide therein under the
pressure of a cam B, which is pivotted to the stock at b slightly out of line with
the centre thereof. This cam bears upon a flanged projection a² on the side of the
sliding die a'. The cam B is actuated preferably by a hand lever extension B¹, and
as this lever is drawn from the horizontal to the vertical position the cam is caused
to advance the sliding die to its work, its increasing radius being thereby brought
round into contact with the die.
The form of this cam it will be seen is such that when its smallest radius is
brought round to the dies the removal of the dies from the stock may be readily
effected, and when its largest radius is brought round to the dies (the moving die.
r

page_text: having then completed its advance) it will serve as a gauge for determining the
exact diameter required for the screw.
The position given to the cam when the dies are required to be adjusted is
shewn at Fig. 4, and the position given to the cam when the utmost limit of feed
is reached is shewn at Fig. 1.
When the dies are set up to the work as shewn at Fig. 3, and the stock is being
moved round the work, the operator will, by a slight pressure on the hand lever B¹,
feed the moveable die forward until the cam lever comes into line with the
handle of the stock. At this time the largest radius of the cam will be brought
into action, and the workman will thus know without inspection that the screw
thread is brought to the required gauge.
By simply throwing the cam lever backwards pressure is taken off the dies, and
the work may be instantly released and a fresh screw blank readily inserted,
and the operation of threading the blank may then be repeated as above explained.
By the use of this arrangement of screw stock it will be readily understood that
the operation of screw cutting may be greatly expedited.
A modification of the Invention is shewn at Fig. 5, where the cam B is made
with a vertical flange, and its bearing surface takes a helical form. This cam
instead of bearing upon the sliding die bears upon the flange of an interposed pressing
piece a³. The rectangular slot in the stock, it will be seen, is rebated at one side in
order to provide for the ready insertion and removal of the pressing piece a³ (see
the cross section, Fig. 5a). This piece a³ when in action is retained in position by
the flange on the cam B. In order to remove this pressing piece the hand lever of
the cam is brought round to the dotted position of Fig. 5, and the smaller radius
of the cam, which has no flange, is thus brought round to the pressing piece,
thereby relieving the pressing piece a³ of pressure, and opening a space for its
removal.
A further modification of the Invention is shewn at Figures 6 and 7, Fig. 6
being a side view, and Fig. 7 a longitudinal section of a screw stock fitted with a
die a for supporting the work, and a screw cutting tool a¹, which is borne down
upon the work by the pressure of a cam B, forming an extension of a handle B¹
having its fulcrum at b. This handle B constitutes one of the pair of handles of
the stock A, and its motion in one direction is limited by a stop pin b'. A
rectangular slot is formed in the stock A to receive the die a, which is retained in
place by vertical guides, as shewn best in the cross section, Fig. 8. This slot is
extended upwards for about half its breadth to receive the cutter a', which also
works in guides, as shewn in the cross section, Fig. 9. In bringing the handle B'
to the position shewn in Figures 6 and 7 the cutter a¹ will be moved to its most
advanced position, and the depth of cut of the screw will be thus gauged as in the
preceding arrangements.
To release the work it will be only necessary to throw back the handle B¹, and
the pressure of the cam B will then be removed from the cutter a'.
Fig. 10 shews a mode of adapting the Invention to the threading of tubes where
no feed motion is needed, but where it is most desirable to disengage the work
from the bite of the dies on the completion of the threading operation instead of
as at present practised, winding off the stock from the work by a back motion.
In this example the dies a, a, are tapered to receive the work, and they are
brought into firm contact before the work is inserted by a cam or excentric B
formed on the pivotted end of the lever handle B'.
The cam or excentric may however be formed with a square pin or socket to
receive a key for putting it into and out of its working position.
When a screw thread of 1, 2, or more inches in length is cut in this stock it
is only necessary to slacken the bite of the cam or excentric B, and the work may
be instantly released from the dies.
Having now set forth the nature of my Invention of "An Improved Construction
of Screw Stock," and explained the manner of carrying the same into effect, I
wish it to be understood that under the above in part recited Letters Patent I

page_text: claim, the application to screw stocks of a gripping cam or excentric arranged and
operated as above described for advancing the sliding die or cutter to or holding
it in contact with the work while the act of cutting the screw is being performed,
and releasing the work from the dies when the screw thread is formed.
In witness whereof, I, the said Percival Everitt, have hereunto set my hand
and seal, the First day of August, in the year of our Lord One thousand
eight hundred and seventy-eight.
PERCIVAL EVERITT. (L.S.)