Improvements in Bolts and Nuts.
Year: 1889

page_text: Date of Application, 12th Nov., 18&9—Accepted, 14th Dec., 1889
COMPLETE SPECIFIGATION.
Improvements in Bolts and Nuts.
I JOHANNES BÜHR of No. 8, Caffamacherreihe, Hamburg in the Empire of Germany,
Machine Maker, 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 bolts and nuts in which the screw of the bolt is used for
cutting the thread of the nut during the screwing of the parts to the nut, in a similar
manner to a screw tap, for the purpose of obtaining an exact and tight fitting.
Such screw bolts have been constructed hitherto with longitudinal groves formed
along the whole lengths of the thread of the bolt and then the latter hardened. The
bolt is thus really a screw tap, which, upon being screwed into the uncut nut, makes
the thread within the nut and thereby effects a close connection between the nut and
the screw-bolt. These screws possess however this drawback, that the grooves
heing 2, 3 or more, the like number of the strips of the thread are lost, the bolt is
provided with an interrupted thread. Naturally the supporting power of the thread
is weakened thereby, and bolts of this kind must be made correspondingly stronger
than the old kind with nut and screw which are each completely screwed.
The object of this invention is to construct a screw bolt, which shall cut the thread
in the nut during the screwing on of the latter and which shall afford a complete non-
interrupted thread within the nut, a thread, which as is the case with the ordinary
screws, retains its full power of support.
The invention for effecting this purpose is set forth in the accompanying drawings,
in which:
Fig. 1. is an elevation of the screw-bolt.
Fig. 2. is a part of the bolt, which carries the thread, partly in section.
Fig. 3. is a plan of the bolt.
Fig. 4. is a longitudinal section through the nut previous to its being screwed on
the bolt.
Fig. 5. is a cross-section through the nut, after the same has been screwed on
the worm.
The improvement consists in arranging at the uppermost part of the screw bolt the
notches a.
These notches are shaped as shown in Fig. 3 so that a sharp edge is on one side,
which after the whole screw or the front part of the same is hardened, acts during
screwing like the cutting edge of a screw-tap. Behind the notches a the thread of
the screw remains uninterrupted, so that after the insertion of the screw in the nut the
complete thread affords support, as shown in Fig. 5.
In order that the nut may be placed on the screw without any special effort, I
fashion the same as it c, as seen in Fig. 4 with completo or nearly complete thread
corresponding in width to the diameter of the screw and tap the part el only slightly,
or also leave it without any thread. It suffices in most cases to cut a few curves in
the nut by the screw bolt, in order to obtain a safe fitting to prevent the nut from
loosening.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
Screw-bolts provided with cutting devices for cutting the thread in an uncompleted

page_text: nut, arranged with cutting grooves or surfaces only at the front part of the screw-
thread, substantially as illustrated and described.
Dated this 12th day of November 1889.
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.