An Improved Device for Removing Broken Screws and the like.
Year: 1889

page_text: Complete Specification Left, 28th Dec., 1889-Accepted, 1st Feb., 1890
COMPLETE SPECIFICATION.
An Improved Device for Removing Broken Screws and the like.
I MAURICE CAHN of Weatherford, Parker County Texas, State United States of
America Gentleman 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 :—
The object of this my invention is to provide a new and improved bit specially
designed for extracting screws taps screw-bolts etc. from iron marble or other hard
substances in case one of the said articles is broken off in the material into which
it is screwed.
The invention consists of a bit provided with an internal spiral cutting thread and
external cutters..
The invention also consists of certain parts and details and combinations of the
same as will be hereinafter fully described, and then pointed out in the claims.
Reference is to be had to the accompanying drawings forming a part of this
specification, in which similar letters of reference indicate corresponding parts in all
the figures.
Fig. 1 is a side elevation of the improvement. Fig. 2 is a transverse section of the
same on the line of Fig. 1. Fig. 3 is a like view of the same provided with a
central Drill and adapted for removing objects broken near the surface of the material.
Fig. 4 is a transverse section of the same. Fig. 5 is a sectional side elevation
of a modified form of the improvement and Fig. 6 is an inverted plan view of
the bit.
The improved bit A is formed of a hollow cylinder screwed or otherwise secured
at one end of a shank B of suitable length and shape and adapted to be turned
by suitable means. The bit A is provided with an internal spiral cutting-thread C,
across which extends a number of grooves D, running lengthwise parallel to the
axis of the cylinder as is plainly shown in Figs. 2 & 5. On the lower end of the
bit A and on the outside, are formed the obliquely-extending cutters E, slightly
bevelled as shown in the drawings. Similar cutters F are formed internally of the
cylinder A, near its lower end, the inner ends of the said cutters terminating at
the beginning of the internal screw-thread C. The cutting thread C and the
cutters E and F are preferably arranged left handed-that is in an opposite direction
to the screws, taps, screw-bolts, etc. to be operated on. In case the latter are left
handed, said thread C, and the cutters E & F are right handed. The bit A is held
removably on the shank B, so as to fasten a bit of any desired size on the said shank.
The size of the bit A is measured according to the internal cutting thread C, which
has a diameter corresponding to the diameter of the screw, tap or bolt to be
removed.
The device is used as follows; when a screw, tap, or screw-bolt, is broken off in a
piece of iron, marble, or other material, the operator selects a bit A of which the
diameter of the internal thread C corresponds to the diameter of the broken off
object. The bit A is fastened on the shank B and the latter by suitable means-
such as a ratchet-dril, wrench, or other device is turned, the end of the hit being
[D011

page_text: inserted in the aperture in which the object is broken off. By turning the shank B
the oblique external cutters E remove part of the material so that the bit A enters the
opening leading to the broken off object. When the end of the bit A comes in
contact with the broken off object, the internal cutters F cut off part of the thread
on the said screw, tap, or screw-bolt, and the cutting thread cuts a new thread on
the object, said new thread extending in an opposite direction to the old thread.
When the bit has cut a sufficient length of thread on the broken-off screw, tap,
or screw bolt, the latter will finally turn with the bit that is in the opposite
direction to that in which its old thread was formed whereby the broken-off object
is screwed out of its aperture and is conveniently removed from the material and
finally from the bit A. The cuttings of the internal thread F pass through
grooves D and in a similar manner the cuttings of the thread C pass through the
said grooves.
When the screw, tap, screw-bolt etc., is broken near the surface of the material,
the operator employes an ordinary drill H fitted into a socket G in the lower end of
the shank B. The cutting-edge of the drill H extends a short distance below the
outer end of the bit A, so that the operator in first drilling causes the drill H to bore
an aperture in the centre of the screw, tap, screw-bolt etc., to be removed until
the cutters E cut into the material surrounding the respective object to be removed. As
soon as the bit A. has a hold in the material the operator, the operator removes the
drill H by inserting the wedge J through a transverse opening I formed in the shank B
said wedge J pressing against the back of the drill H, (See Fig. 4). The above
described operation is then repeated.
When the operator desires to probe for a broken-off tap screw screw-bolt
etc., he uses a bit A without the external cutters E as shown in Fig. 1. The
cutters E are left off so that the thread already cut in the material will not be
spoiled.
It will be seen that a very simple device is provided for conveniently and quickly
removing screws, taps, screw-bolts, etc., broken off in the hard material. As any sized
bit A may be employed the device ranges from the smallest screws and taps to very
large ones.
The device is equally useful for a watchmaker and for Artesian well borers.
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. A bit for extracting broken screws etc. provided with an internal spiral cutting-
thread and external cutters substantially as shown and described.
2. A bit for extracting broken screws etc., comprising a hollow cylinder having an
internal spiral cutting-thread and oblique cutters formed externally on one end of
said cylinder substantially as shown and described.
3. A bit for extracting broken screws, etc., comprising a hollow cylinder, having
an internal spiral cutting-thread, and oblique cutters formed externally on one end
of the said cylinder, and bevelled oblique cutters formed internally on one end of the
said cylinder substantially as shown and described..
4. A bit for extracting broken screws etc., formed of a hollow cylinder having an
internal spiral cutting-thread, and grooves formed across the ridges of said thread,
substantially as shown and described.
5. A bit for extracting broken screws etc. comprising a hollow cylinder having
internal spiral cutting thread, and grooves formed across the ridges of said thread,
and beveled oblique cutters formed externally on one end of the said cylinder sub-
stantially as shown and described.
6. A bit for extracting broken screws, etc., comprising a hollow cylinder having
internal spiral cutting-thread and grooves formed across the ridges of the said thread,
beveled oblique cutters formed externally on one end of the said cylinder, and bevelled
oblique cutters formed internally on one end of the said cylinder, substantially as shown
and described.

page_text: 7. The combination, with a shank, of a bit held on the said shank and comprising
a hollow cylinder having internal spiral cutting thread and grooves formed across
the ridges of the said thread and beveled oblique cutters formed externally on one end
of the said cylinder substantially as shown and described.
8. The combination with a shank, of a bit held on the said shank and comprising
a hollow cylinder having an internal spiral cutting thread and grooves formed across
the ridges of said thread bevelled oblique cutters formed externally on one end of the
said cylinder, and a drill held in a socket on the said shank, and projecting below
the end of the said bit, substantially as shown and described.
Dated this 28th day of December 1889.
HORN & SON,
Applicant's Agents.