IMPROVEMENTS IN SCREW CUTTING APPARATUS
Year: 1876

page_text: LETTERS PATENT to William Phillips Thompson, of 6, Lord Street, Liverpool,
in the County of Lancaster, British and International. Patent Agent and
Consulting Engineer, for the Invention of "IMPROVEMENTS IN SCREW CUTTING
APPARATUS." A communication from abroad by Samuel Webb Martin, of
Springfield, Ohio, one of the United States of America.
Sealed the 8th May 1877, and dated the 18th November 1876.
COMPLETE SPECIFICATION filed by the said William Phillips Thompson at
IM-
the Office of the Commissioners of Patents on the 18th November 1876.
WILLIAM PHILLIPS THOMPSON, of 6, Lord Street, Liverpool, in the County of
Lancaster, British and International Patent Agent and Consulting Engineer.
PROVEMENTS IN SCREW CUTTING APPARATUS." A communication from abroad
by Samuel Webb Martin, of Springfield, Ohio, one of the United States of
America.
My Invention consists in a screw cutting tap and die, having their cutting jaws
so pivoted that they may be swung back and disengaged from the object in or on
which the thread is cut, in combining with the cutting jaws of a tap detachable
cutting lips, by which the hole can be reamed out at the same time or by the same
operation that cuts the thread; in providing the cutting jaws of a screw cutting die.
with threads on both ends; in providing each jaw with right-hand threads on
one end, and left-hand threads on the other, in rings adapted to fit within the
head or stock, and enable the same to hold die cases and dies or jaws of different
sizes; in the peculiar form of the dies, and in other minor features herein-after
dicribed.
Fig. 1 is a side elevation of the tap complete; Fig. 2 is a longitudinal section of
the same on the line x, x, of Fig. 3; Fig. 3 is an end view with the cap or end
piece removed, and Fig. 4 a view of one of the cutting lips detached, and Fig. 5
represents a face view of my improved die, with portions shown in section to
illustrate more clearly the internal construction.
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Fig. 6, a perspective view of the die case or ring with the dies therein, one side

page_text: being lifted to show the internal construction, and Fig. 7 a face view of one of the
rings employed to reduce the internal diameter of the stock or head.
To construct my improved tap which forms the first part of my Invention, I
provide a mandril or stock A, which consists of a round bar of proper size, having
a slot transversely in its end of a size to receive the jaws, as represented in Fig. 2
and 3, I then provide a tubular sleeve B of a size to fit closely but loosely over the
slotted end of the stock A, which has a slot in its opposite sides of such a size as
to permit the jaws to fit therein. I then provide two jaws C of the requisite length
and size made slightly tapering, and having screw cutting teeth formed on the
outer edges, said teeth extending from the rear end of the jaws forward for two-
thirds or more of their length, as shown in Fig. 1. At their front ends a recess is
formed on the outer edge, and extending a short distance down on their front side,
in which is fitted a cutting lip e, as shown in Fig. 1, 2, and 3, the lip being shown
detached in Fig. 4. Immediately in rear of these lips the edge of the jaws is left
smooth and flush with the outer face of the lip e, thus forming a bearing to guide
and steady the jaws in their operation, there being a slight depression C in the outer
face of the jaws between this bearing point a and the teeth, as shown in Figs. 1
and 2. Upon their inner edges these jaws C are beveled, as shown in Fig. 3, so as
to permit them to swing or turn on their pivots or bearings n. The pivots n are
arranged as shown in Fig. 2, those at the rear end being fixed permanently in the
stock A, and those at the front end being held by a cap I, which is preferably
made detachable, and secured in place by screws and a flange fitting in a recess
turned for it on the end of the stock so as to secure it firmly in place, though it is
obvious that this cap I may be omitted, and the end of the stock left solid if
preferred, the outer pivots being formed with screw threads, as shown in Fig. 2, so
they can be screwed in or out at pleasure to insert or remove the jaws.
By examining Fig. 3 it will be seen that along the slot in which the jaws are
fitted the edge or shoulder of the stock is cut away or bevelled off as at v along
the front side of each jaw, the object being to permit the jaws to swing laterally as
indicated by the dotted lines in Fig. 3. Two pins-o are inserted obliquely across
the slot, as shown in Fig. 3, on which the inner edges of the jaws bear when turned
so as to stand radially or in working position. In cases where the tap can be
inserted but a short distance, and it is desired to cut the thread all the way, the
jaws will be made without the boring or cutting lip e, and the teeth made to extend
to the front end, as shown in the lower side of Fig. 2. The sleeve being loose on
the stock will turn thereon as the jaws are swung either way, and fitting close to
the jaws it covers the recesses in front of the jaws and prevents chips, &c., from
entering. These tools may be made of any size required, and each stock can be
provided with sets of jaws differing in width from the pivote outward in graduated
sizes, so that with one tool thus provided holes of various sizes may be tapped. The
jaws are easily and cheaply made, and can be very quickly sharpened by grinding
their front faces.
It will be seen that when thus constructed and arranged the jaws when standing
radially, as they will when the tool is being used, will be firmly supported by the
wall of the slot on their rear face, which bears against them to the outer edge of the
stock, their lower front edges at the same time bearing against the opposite wall of
the slot, thus holding them firmly in position, the cross pins o at the same time
preventing them from being forced inward.
If desired, instead of the pins o, a solid flat piece may be inserted the whole length
of the slot, its edges fitting in recesses made for it in the opposite wall, or a solid
cross piece or portion may be left when the slots or recesses are cut in the stock for
the jaws. The pins o, together with the pivots n, which latter if preferred may be
cylindrical instead of pointed, are found in practice to be sufficient. To use the
tool it is simply inserted in the hole and rotated in the direction indicated by the
arrow in Fig. 3. When the thread is cut the motion is reversed, which causes the
jaws to assume the position indicated by the dotted lines, thus throwing their outer

page_text: edges inward as they are pivoted eccentrically, which withdrawe the teeth from the
threads, thus permitting the tool to be withdrawn without screwing it out as in the
case of ordinary taps.
The second part of my Invention is the screw cutting die, of which A represents
the stock or body of the tool made in an annular or ring form, and provided in its
inner face with recesses a¹ to receive the outer ends of the pivoted dies or bite;
B¹ represents the die case or holder, also made of an annular or ring form, with an
open center, and fitted loosely within the stock A in such manner that it may be
rotated therein to a limited extent; C₁ represent the dies or cutting bits; consisting
of flat straight pieces of steel pivoted in the case or ring B', with their outer ends
resting in the notches a¹ in the stock A', and their inner ends protruding into the
central opening of the ring or case B¹, as shown in Figures 5 and 6, the inner ends
being provided with cutting threads or teeth.
The arrangement of parts is such that upon turning the ring or case B¹ within
the head or stock A¹ in one direction, the dies are turned on their pivots so as to
throw their cutting ends inward in position for action, as shown in Fig. 5, while
upon turning the case in the opposite direction the ends of the dies are thrown
outward, so that they realise instantly the rod, tube, or other object on which they
have cut a thread, allowing the same to be withdrawn without a reversal of the
motion of the machine.
As a means of turning the case or ring B₁ to actuate the dies or bits, a hand
lever El is passed through a slot in the head or stock A¹ and inserted into a hole or
socket in the case, as shown in Fig. 5.
In order to limit the motion of the dies on their pivots and to sustain them when
in action, the case B₁ is constructed with shoulders d', el, against which the dies
bear when in their operative position, as clearly represented in Fig. 5 and 6. The
pivots of the dies may be formed on their edges or passed through them, but in
order to simplify the construction and leave the dies as strong as possible I prefer
to provide the dics with conical recesses f¹ in their edges, and the side plates of the
case B with solid conical pivots g¹ to enter the same, as represented in the
Drawings. The dies may be made with teeth on one end only, or on both ends, in
which latter case they will be arranged to be reversible end for end, so that either
end may be used at will. By thus providing the dies with teeth or threads on both
ends and making them reversible, the steel required to form an ordinary single die is
made to serve all the purposes of two separate dies.
In the event of one end of a die becoming injured or worn it is simply reversed
instead of being thrown away as usual, and the tool is again as perfect as before.
If desired, each die may have a right-hand thread on one end and a left-hand
thread on the other, so that by simply turning them end for end in the case B¹ and
then turning the case the other side out in the body or stock A¹ the tool may be
readily adjusted for cutting either a right or a left-hand thread as desired.
In order to adapt the same dies for threading rods or tubes of two different sizes,
they may be given a grater length on one side of their pivots than on the other, so
that they will be adapted for threading large or small objects according as their
long or their short ends are brought into action.
In order to enable the head or stock A¹ to receive and hold cases of different,
diameters, internally adapted for threading objects of different sizes, I provide a
series of rings D¹, such as represented in Fig. 7, adapted to fit within the stock, and
provided with outside studs c¹ to enter the recesses a¹ therein. These rings will all
be made of the sanic external diameter, but their internal diameters will be varied
to suit the different cases which it may be desired to use therein. Each ring will be
provided with internal recesses a¹¹ to receive the studs on the outside of the case in
the same manner that they are received and held in the stock or body as shown in
Fig. 5.
Instead of making all the rings of a diameter to fit the stock A¹ they may be
arranged to fit one within another, this latter arrangement reducing the weight of

page_text: the rings and permitting them when not in use to be packed in a compact nest.
The rings and the case B¹ may be secured in place by buttons d' as shown, or by
any other device which will admit of their ready insertion and removal. The tool
as represented in the Drawing is intended more especially for use in a power
machine, the rod, tube, or other object to be threaded being given a rotary
motion, and the stock or head A being secured rigidly in place so that the attendant
may operate the lever E at any moment, and thereby throw the dies into and out of
action while the machine is in motion.
'
The same principle of construction and arrangements of parts shown in the
Drawing may of course be applied in tools to be operated by hand as well as in
those to be used in machines. It will be observed that the dies or bits shown in
the Drawings consist simply of plain pieces of steel, having no irregularities or pro-
jections, and that consequently they can be cut from the end of plain bar steel.
and manufactured very cheaply.
In order to prevent the entrance of chips or other foreign matters into the
working parts, a sliding sheet metal shield G₁ is fitted within the case or ring B¹
closely around the dies as shown, so that while it slides and permits the movement
of the dies, it effectually prevents chips, &c., from entering by their sides. When
the tool is to be held stationary the shield need only be placed in the lower side as
shown, but when the tool is to be rotated the shield must of course be extended
around the entire outside face of the case.
It is obvious that in constructing my tool the form and arrangements of parts
may be modified provided the operation remains substantially the same.
Having thus described my Invention, what I claim is,―
1. A screw cutting tap, consisting of a stock or mandrel A with the screw
cutting jaws C pivoted eccentrically therein, said stock and jaws being constructed
to operate substantially as described.
2. In combination with the stock A and the pivoted jaws C, the loose sleeve B
arranged to operate as set forth.
3. In combination with the pivoted jaws C, the supporting pins O, or their
equivalent, arranged to operate substantially as described.
4. In combination with the stock A and the pivoted jaws C, the cap or end piece I,
constructed substantially as set forth.
5. The pivoted screw cutting jaws C having the detachable cutting or boring
lip e constructed and applied thereto, substantially as shown and described.
6. In a screw cutting tap, one or more screw cutting jaws pivoted so as to swing
laterally on its bearings or pivots, substantially as described.
7. In a screw cutting die the combination of an annular case or ring B¹, a series
of dies or bits C₁ pivoted eccentrically therein, and a head or stock A¹ constructed
and arranged to engage with and operate said dies, substantially as shown.
8. The combination of the stock or head A¹ having the internal recesses a¹, the
annular ring or case B¹ arranged to rotate within the stock A', and the dies C¹
pivoted in said case and entering the recesses as shown.
9. In combination with the stock A¹ having the internal recesses a¹, the ring or
case B¹ mounted therein and provided with the pivoted dies C¹, and with the
shoulders & and e¹ to sustain the same when in action.
10. The reversable pivoted dies C₁ provided with threads on both ends, and
arranged to operate substantially as shown and described.
11. A screw cutting tool provided with dies reversible end for end, said dies
having right-hand threads or teeth on one end and left-hand threads or teeth on the
other, substantially as shown and described.
12. In combination with the stock or head A¹ provided with the recesses a¹, the
ring B¹ provided with the external studs C₁ and internal recesses a¹¹, whereby the
stock is enabled to hold die cases of different sizes.
13. In combination with the annular case or ring B¹ and the dies C¹ pivoted
therein, the internal sliding guard plate or shield G¹, mounted therein as shown.

page_text: 14. The pivoted dies C¹, each consisting of a plain flat plate of steel provided
with teeth on one or both ends, and with a hole or recess to receive the pivots.
In witness whereof, I, the said William Phillips Thompson, have hereunto set
my hand and seal, this 16th day of November, in the year of our Lord
1876.
Witness,
EDWARD G. COLTON,
Patent Office,
6, Lord St.,
Liverpool
W. P. THOMPSON. (L.S.)