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Oct. 1, 1946.
Filed June 7, 1944
. Fig.5
Y'C/z'aim Lieb/ei'n
Patented Oct. 1, 1946
Chaim Lieblein, Brooklyn, N. Y.
Application June 7, 1944, Serial No. 539,068
1 Claim. (01. 10-141)
This invention relates to an improved screw
The end stud 1 is considerably smaller than
tap and one of its objects is to lower the cost
the head 6, and the surface of the forward end
of producing taps for forming screw threads in
of the head is disposed at right angles to the
large diameter tubes and holes.
axis of the shank, and thus provides a thrust
It is at present the common practice to form
shoulder or bearing surface 8.
screw thread cutting taps upon a solid piece
The cutting disk 9 is formed with a central open
of tool steel, so as to provide the necessary
ing 9a, which has a form corresponding, to that
thread cutting teeth and a shank for holding and
of the stud 1, and is positioned on the stud 1
operating the tool. When the threads are broken
and against the thrust or hearing shoulder 8.
or otherwise rendered useless the whole tool must 10 The forward end of this disc is formed with a
be rejected, or subjected to a complete regrinding
circular recess 9a which snugly receives the
or retooling operation. Screw taps of this type
washer l0, and this washer is formed with a coun
are not adapted for use in forming screw threads
tersunk opening Illa which receives the screw ll.
in large diameter tubes and holes.
having a countersunk head Ila, and this screw is
My improved screw tap tool consists of a disk 15 threaded in the stud ‘I, so as to secure the disk 9
of hardened and ground steel suitable for this
on the stud 1 and against the shoulder 8.
purpose, and a shank having a square stud which
The disk 9 is formed with a plurality of rows
snugly ?ts in a square hole formed in the tool
of screw thread cutting teeth 12, and in the con
disk and a screw and washer set for holding the
struction shown there are four rows of such
disk on the square stud, so that it may be re
teeth, the rows being equally spaced from each
moved and replaced with a new disk, or one of
other. The disk is relieved at l3, in advance of
smaller size, or for a different screw thread.
the leading or cutting edges of the teeth so that
Another object of the invention is to provide
an e?icient cutting action will result, and the for
a screw tap, which includes a screw thread cut
ward or cutter side of the teeth l2 are disposed
ting disk, which can be' arranged in multiples or 25 in a slight pitch to aid in effective thread cutting.
gangs upon a squared shaft, ‘so that the screw
The cutting disks are formed from circular
threads may be cut or formed, as by milling or
blanks M of .tool steel, each having a square cen
grinding the whole group or gang at one time.
ter hole Ma.‘ These blanks are mounted on the
With the above and other objects in view the
square shank or mandrel l5, clamped against
invention comprises certain new and useful con 30 each other, and then the screw threads are out
structions, combinations and arrangements of
upon all of the disks at one time. The disks are
parts, clearly described in the following speci?ca
tion, and fully illustrated in the drawing, in
then subjected to the usual ?nishing operations,
when they are ready for use.
I have found that my improved method of
Fig. 1 is a side elevation of the combined tool. 35 manufacture materially reduces the cost of form
Fig. 2 is an end view showing the disk, hold
ing the screw tapping disks, and that it is more
ing washer and its connecting screw.
economical to replace a disk having broken teeth,
Fig. 3 is a detail plan view of the washer. .
than it would be to purchase a large screw thread
Fig. 4 is a detail sectional view thereof.
tap'of-corresponding size and capacity.
Fig. 5 is a detail side view of a holding screw.
Having described my invention I claim as new:
Fig. 6 is a central vertical sectional view show
A thread cutting tool, comprising a shank
ing the combined tool.
having a polygonal stud on one end thereof and
Fig. 7 is a plan view of the disk removed from
I a shoulder at the inner end of said stud, said
the holding shank.
stud being disposed centrally of the shank, a disk
45 having a central opening which receives the
Fig. 8 is an end view of the tool shank;
Fig. 9 is a side view of a gang of blank disks
polygonal stud and disposed against said shoul
arranged for milling the teeth on all disks in one
der, said disk having a plurality of radial lands
Fig. 10 is a plan view of one of the blank disks.
provided with screw‘ cutting teeth, and also
formed with a recess concentric with said central
opening, a washer disposed in said recess and
engaging the outer end of the stud, and a screw
Referring to the accompanying. drawing il so
lustrating the practical construction of the in
vention, 5 designates a shank of tool steel, which
extending through the washer and threaded into
is provided with an integral head 6 and an end
the stud 'for retaining the disk on the stud be
stud ‘I, centered axially thereon, and formed with
tween said washer and said shoulder.
a plurality of parallel sides, resulting from the 55
milling of the stock from round to square or
other polygonal form.
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