Improvements in Automatic Screw-cutting Dies.
Year: 1890

page_text: Date of Application, 13th May, 1890-Accepted, 12th July, 1890
COMPLETE SPECIFICATION.
Improvements in Automatic Screw-cutting Dies.
I, GEORGE LIGOWSKY, of the Town of Cincinatti, in the County of Hamilton and
State of Ohio, Engineer, do hereby declare the nature of my said invention, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
My invention relates to that class of dies to be used as lathe tools and inserted in a
sliding head, usually a monitor, to be advanced up to and operate upon the work which
is secured to and revolved by the lathe spindle. It has for its object an improved con-
struction, by which, when the thread has been cut to the proper distance, the cutters
are automatically thrown apart to release the work from their action.
The novelty of my invention will be herein set forth and distinctly pointed out in
the claims.
In the accompanying drawings,
Figure 1 is a front elevation of a die embodying my invention,
Figure 2 is a rear elevation of the same,
Figure 3 is a side elevation of the same partly in section,
Figure is a plan view of the die.
The same letters of reference are used to indicate identical parts in all the
figures.
The body of the tool is composed of a vertical face plate A, from which projects
horizontally a shank B for insertion in the sliding head to which it is locked. A
central recess C is formed through the face plate and back into the shank to receive
a sliding and partially turning thimble D interiorly threaded and provided with a
pin a, which projects up through an inclined slot b, Figures 3 and 4, in the shank, as
shown. Screwed into the thimble D is a tubular plug E, interiorly threaded to
engage a jam screw F which is inserted through it and bears at its rear end against
the inner wall of the thimble to lock the plug when adjusted in the thimble, as will be
readily understood.
Pivoted at their lower ends upon the front of the face plate A as at d are two
jaws G, G¹, which, when brought together in a vertical position, have a central
opening e coincident with the recess (in the face plate and shank.
Secured in the jaws G, G' and adjustable by set screws fare four cutters H projecting
into the opening e and constituting the screw cutting die. While I have shown the
cutters to be each independently adjustable the die may be in two parts and of the
shape usually employed in screw cutting and with each half adjustable. The upper
ends of the jaws G, G¹ are preferably provided with grasping handles 9 to draw the
jaws together after they have been automatically thrown apart to the position indicated
by the dotted lines in Figure 1, and h, h, are stop rods secured to a lug i upon the
face plate and passed through perforations in the handles g and having buttons or
heads upon their outer ends to arrest the jaws when thrown open. I is a stop screw
secured in the face plate and serving to arrest the jaws in proper position when drawn
together as well as to support the upper ends of the jaws against tension.
Projecting from the rear upper side of the jaw G³ is a lug j, in which is pivoted a
latch K normally pressed forward by a spring 1 and having serrations or engaging
points, which, when the jaws are brought together, engage with a similarly serrated or
notched adjustable arm n secured to a lug o projecting from the upper rear side of the
jaw G in such manner as to hold the jaws firmly locked during the operation of the
die. A spring p secured to the under side of the face plate bas its two ends extending
up and engaging under tension the inner sides of the lugs j, o. While have
shown but one spring it is evident that there may be two, one for each jaw.
Pivoted as at to the shank B, and as at s to an upper rear projection of the face

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plate is a vertical trigger piece J, having a lower rear extension or curved finger t
engaging the rear side of the pin a.
When the jaws are locked together the latch K bears against the trigger J and the
finger t bears against the pin a holding it in the forward extremity of the slot b.
Now when the tool is advanced to the revolving work and the thread has been
cut to the proper distance the further advance of the tool causes the work to come in
contact with the plug E, which, by frictional contact, is simultaneously turned and
forced back, thereby and through the medium of the thimble F, moves the pin a and
vibrates the finger and trigger piece J, and thus forces the latch & out of engagement
with the arm n, and thereby frees the jaws which are at once thrown apart by the
action of the spring p to the position shown by the dotted lines in Figure 1.
This throwing apart of the jaws frees the work from the cutters and is drawn where
there is a shoulder at the end of the thread, which prevents the stripping or injury of
the cut thread. By adjusting the plug E the jaws can be thrown apart for shorter or
longer threads as desired.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1. In a die, the combination, with a recessed face plate and shank, of two pivoted
jaws carriyng the cutters and held together against spring tension, a lock for said jaws,
and a trigger for breaking the lock, operated by the work to automatically release and
throw the jaws apart, substantially as described.
2. In a die, the combination, with a recessed face plate and shank, of two pivoted
jaws carrying the cutters a lock to hold said jaws together in proper working position,
a spring put under tension by the locked jaws, a trigger for the lock, and a plug
within the recess provided with means for pressing the trigger to break the lock,
substantially as described.
3. In a die, the combination and arrangement of the face plate A and shank B
provided with recess C, jaws G, G₁ pivoted to the face plate and carrying cutters H,
the spring p engaging said jaws, the notched bar n and spring latch k, the trigger J,
and the thimble F with its adjustable plug E, and pin a engaging the trigger J,
substantially as and for the purpose specified.
Dated this 9th day of May 1800
GEO. DOWNING,
8, Quality Court, London, W.C., Agent for Applicant.