Improvements in Machines for Forming Cutting Faces upon Dies, Taps, Mills, and similar Tools.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Machines for Forming Cutting Faces upon Dies,
Taps, Mills, and similar Tools.
I, FRANK ARMSTRONG, Manufacturer, residing at 110 William Street,
Bridgeport, State of Connecticut, in the United States of America do hereby
declare the nature of this invention 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 certain new and useful improvements in machines for
forming the cutting faces upon dies, taps, mills, and similar tools, and the objects
of this invention are, to provide means for automatically feeding the cutter into
engagement with the work, and for insuring the accuracy of the finished dies or tap
faces, but principally it has for its object to cause the cutter to so move relative to
the work that the cutting faces left upon the latter shall be relieved. By relieving
these cutting faces is meant the formation thereof in a curved line which, while it
may be a part of a true circle, is eccentric to the centre about which the dies will
A die thus
revolve when in operation, as in threading the end of a pipe or bar.
relieved cuts a much cleaner thread and cuts it with less friction than a die whose
cutting faces are concentric with the tube or pipe upon which they are designed to
operate. With the ends hereinbefore set forth in view my invention consists in the
construction and combination of elements hereinafter fully explained and then
recited in the claims.
In order that those skilled in the art to which my invention appertains may fully
understand its construction and operation, I will describe the same in detail,
reference being had to the accompanying drawings which form a part of this
Specification, and in which,
Figure 1, is a side elevation of my machine,
Figure 2, a similar view from the other side;
Figure 3, a plan view.
Figure 4, a vertical section at the line -x of Figure 1,
Figures 5 and 6, are elevations of the pattern ring but showing in diagram the
positions of the dies, the cutter, and the roll upon which the pattern ring operates.
These two figures correctly represent the positions of the several parts as they
would appear if one could look through the machine from the line y-y of Figure 2
in the direction of the arrow.
Figure 7, a section on the line - of Figure 3,
Figure 8, a plan view of a machine similar to that of the preceding figure, but
adapted for producing taps,
Figure 9 a section on the line v- of Figure 8, somewhat enlarged,
Figure 10, a transverse section showing the application of my invention to a
lathe, the latter being shown as in use for producing milling cutters.
Like numerals denote the same parts in all the figures.
Referring now particularly to Figures 1, 2, and 3, 1 is the supporting bed or
frame-work adapted to carry the moving parts of the machine. Journaled in an
upright or standard 2 is a shaft 3 provided with a head 4, said head adapted for
the attachment of the die-blanks 5 whose faces it is desired to form in such manner
that when mounted in a suitable stock they shall properly co-operate to cut a
thread upon a pipe or bar. These blanks are shown at Figure 4 and are attached
to the head by means of screws 6. Behind the standard 2 a worm-wheel 7 is
carried upon the shaft 3, and said worm-wheel is driven by means of a worm-gear 8
journaled transversely in bearings on the bed beneath said worm-wheel, said worm-
gear being in its turn driven from a band-pulley 9 at one side of the bed through

page_text: the medium of a pair of beveled gears 10. 11 is a band-wheel journaled about the
shaft 3. This band-wheel has nothing to do with the working of the machine,
except to back off the cutter so as to begin a new operation. In front of the band-
wheel 11 will be observed a toothed clutch, and at the rear of said band-wheel a
ratchet-wheel 14 upon whose periphery a pawl 15 is operated by the shaft that
carries the band-wheel 9. I have shown these parts because they are intimately
associated with the other parts of the completed machine, but they form no part
of my present invention. The rear extremity of the shaft 3 carries a gear 12
which through gears 12, 13, and 13ª iniparts rotary movement to the feeding
screw 14 which is hung in bearings along the side of the frame. 16 is a carriage
mounted upon the bed and adapted to be fed longitudinally thereon by means of
the feed screw 14 which passes through a projection upon said carriage which is
marked 17 at Figure 4. This carriage supports a sliding plate 18 upon which is
mounted a head 19 adapted to be moved upon ways 20 by means of a feeding
screw 21 whose operation is supplemented by a rod 22 and check nuts 23, these
latter being for the purpose of fine and close adjustment and for limiting the
movement. As shown at Figure 7 a binding screw 24 abuts against the rod 22
for the purpose of securing the head rigidly in position when finally adjusted.
25 is an arbor journaled vertically by means of any ordinary screw mechanism,
such as shown at 26, and upon its rear end it carries a band-wheel 27. The
forward end of this arbor is adapted to receive and carry the milling cutter 28 by
means of which the cutting faces are formed upon the dies.
The mechanism heretofore described is competent to produce finished and
properly threaded dies, but said dies will have their cutting surfaces concentric,
which, as heretofore explained, is undesirable: I will now explain that portion
of my machine by means of which the relieving is accomplished.
30 is
29 is a ring which is detachably secured upon the rear of the head 4 by any
suitable means.
The interior conformation of this ring is shown at Figures 5 and 6,
and it consists of an irregular line made up of a plurality of curves, each of which
is preferably a part of a true circle, but no two of which are struck from the same
centre. This makes the interior contour of the ring a series of cam surfaces.
a lever, see Figures 2, 3 and 4, whose upper extremity carries a roll 31 which
latter projects into the ring from the rear and is adapted to rest against and to be
moved slightly by the irregular outline of the latter. The lower end of this lever 30
embraces and is secured upon a rock shaft 32 whose journal bearings are in an
outwardly extending bracket 33, as shown at Figure 4. 34 is a rock arm or lever
likewise made fast upon the shaft 32 and extending upward through an opening 35,
in the bracket 33. The upper end of this lever engages a mortise in the slide
plate 18, and a set screw 36 takes up lost motion between the end of said lever
and the plate. 37 is a flat steel spring whose extremities are secured to the face
of the carriage 16, as seen at Figures 1 and 3, a projection from the edge of
said spring taking into the bottom of the carriage 18, as seen at Figure 4, 80
that any movement of the plate 18 toward the left of Figure 4 will be made
against the power of the spring which latter will tend to restore it to its normal
position when the applied force is removed.
Secured upon the bracket 33 is a tapered bar 38 which is held thereon by means
of screws, bolts, or other suitable fastenings. 39 is a similar bar which is arranged
so as to form a continuation of the inner surface of the bar 38, but at an obtuse angle
to the latter. The inner surface of these two bars are engaged by the extremity of
a projecting shoe or rod 40 which is attached to or forms a part of the plate 18.
The purpose of this arrangement is to give to the cutting surface of the dies when
finished not only the very gradual taper appropriate to a well-formed threading
die, but also to impart to said cutting surfaces at one end a sharp taper whereby
the rod or pipe to be threaded may be readily introduced between the dies.
The operation of my invention is as follows. The blanks upon which the cutting
faces are to be formed are first secured to the outer surface of the head, as shown
at Figure. The carriage 16 is then run back upon the screw 17 until the milling

page_text: tool is in position to commence cutting, and then by means of the screw 21 the
head 19 is properly adjusted transversely of the machine. The cutting tool is then
started, and likewise the head 4 which rotates very slowly. As will be observed
by the Figures 5 and 6, the milling cutter first comes in contact with the heel or
rear end of the cutting face. When it comes in contact with the first die-point the
roll upon the lever 30 is upon a high point of one of the cam surfaces on the ring,
see Figure 5. This, by means of the rock shaft 32 and the lever 34, has crowded
the plate 18 toward the left of Figure 4 so that the bite of the milling cutter takes
into the stock of the blank to a considerable depth. This will be understood by
reference to Figure 5 where the position of the milling cutter and the position of
the ring and roll on the lever appropriate to produce this position of the milling
cutter are shown in diagram. Of course it is understood that the transverse
movement of the plate 18 is made against the spring 37 which tends constantly to
throw the plate in the opposite direction toward its normal position. As the ring
and the die blanks revolve still further in the direction of the arrow, as appears on
Figures 5 and 6 the roll on the lever descends from the high point of the cam
which caused it to bite deeply, and as the spring 37 crowds the plate and its
attached parts backward, the bite of the cutter becomes less and less, until at the
extreme point of the cutting face it is at its least depth, as seen at Figure 6, at
which time the roll is in contact with a low portion of the cam surface of the ring.
When the head carrying the ring and dies has further advanced so that the cutter
arrives at the next point of the blank, the roll will be again at a high point, and
will therefore begin its cut with a bite of its greatest depth by reason as heretofore
explained, of the fact that the plate 18 and the cutter are crowded over against the
spring to the greatest distance, that is, toward the left of Figure 4."
movement of the head and ring is very slow, the to and fro traverse of the cutter is
very gradual as well as very slight, and the movement of the outer end of the
lever 30 is reduced in the movement of the cutter by reason of the discrepancy in
length between said lever 30 and the lever 34.
As the
In addition to the relieving of the die faces which has just been described, it is
necessary to impart to the cutting surface of the die not only the very gradual
straight taper of its face, but also the somewhat sharper taper by means of which
the ready insertion of the work is permitted. This is accomplished by means of
the two guiding bars 38 and 39 which act upon the plate 18 so as to steadily and
gradually carry the cutter more deeply against the work, as the cut advances.
When the cut is commenced the carriage of course is at its extreme position at the
right of Figure 1. The shoe 40 will therefore be at the lowest point of the inclined
bar 38. As said carriage 16 is fed forward towards the left of Figure 1 by means
of the screw 14, it will be readily understood that the action of the shoc against the
inclined surface of the bar will gradually crowd the plate 18 more and more toward
the left of Figure 4, thereby forming a straight taper on the surface of the die.
When the carriage 16 has been fed forward by the screw 14 far enough so, that
the shoe arrives at the sharper incline of the inner surface of the bar 39, the same
crowding movement still continues but more rapidly, whereby the last end to be
cut will be considerably deeper so that the dies when in operation may readily
receive the work.
In Figures 8 and 9 are shown a machine precisely similar to that in the preceding
figures, except that the head 4 is arranged to accommodate a tap instead of a
plurality of dies, said tap being hung in bearings and held as against rotation
independent of the head by means of an ordinary dog or other suitable device. As
this is identical in principle it would appear that no further or more detailed
explanation is necessary.
In Figure 10 I have shown the cross slide of the preceding figures applied to a
lathe, the turning tool of which is shown as relieving the cutting faces of a circular
mill in substantially the same manner as has been heretofore described, that is to say,
the mill being rotated against the turning tool which latter has imparted thereto,
by means of the cam 29, a sliding movement toward and away from the work.

page_text: In this my invention I do not wish to be confined to the exact details of
construction herein shown and described, since it is apparent that the method of
operation which forms the gist of my invention may be applied in various ways
either to lathes, or other machines, without departing from the combinations recited
in the clauses of claim now to follow.
Having now particularly described and ascertained the nature of my Baid
invention, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a machine of the character described, the combination with the rotative
head and means for attaching the blanks thereto, and the milling cutter, of a cam,
and a connection between said cam and the milling cutter, whereby the latter in
addition to its other appropriate movements shall have a traversing motion,
substantially as described.
2. In a machine as described, the combination with a rotative head, and means
for securing the die blanks thereon, of the milling cutter, means for feeding the
same longitudinally, a traversable plate upon which said cutter is mounted, and a
pattern cam, and a connection between said cam and the cutter plate whereby the
latter receives a to and fro movement transversely to the length of the machine,
substantially as described.
3. The combination with a rotative head, of the cam ring carried thereby, the
rotative cutter and its traversable carriage, and means as levers interposed between
said cam ring and the carriage whereby the latter is given a to and fro movement
at right angles to its forward feeding movement, substantially as described.
4. In a machine of the character described, the combination with a rotative head
adapted to carry the die blanks, of the cam carried by said head, a rock lever
obtaining movement from said cam, a traversable tool-carrier, and a connection
between the cam-operated lever and said tool-carrier, whereby the latter has
imparted thereto a movement transverse to the length of the machine, substantially.
as described.
5. In a machine as described, the combination with the rotative head adapted to
carry the die blanks, of the leverage system comprising the parts 30, 32 and 34,
the traversable tool carrying plate engaged by the lever 34, and a spring engaging
the other end of said plate, substantially as described.
Dated this 19th day of May 1891.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.