AN IMPROVEMENT IN SCREWED BOLTS AND NUTS
Year: 1885

page_text: I, JOHN IMRAY, of No 28 Southampton Buildings, Chancery Lane in the
county of Middlesex, Consulting Engineer and Patent Agent, do hereby declare
the nature of my invention for "AN IMPROVEMENT IN SCREWED BOLTS AND NUTS"
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
When screwed bolts and nuts are subjected to shakes, as for example when they
are used to clamp the fish plates connecting rails, they are apt to become loose, the
nut unscrewing itself. It has therefore been desirable to provide for such cases,
"lock-nuts" or self locking bolts and nuts, so arranged that when the nut is
screwed home, it shall be held permanently in position without tendency to unscrew
itself. In some cases a nut has been slit throughout its depth on one side and
screwed a little smaller than the bolt so as to be sprung a little open when
screwed on, its elasticity causing it to clamp the bolt within it; in some cases a
nut has been slit along part of its depth and the metal on each side of the slits
has been forced inwards to clamp the bolt; and in some cases part of the screw
thread of the bolt has been increased in diameter so as to cut or force its way into
the thread of the nut. This invention relates to the construction of a partly slit
nut to be used in conjunction with a somewhat tapered bolt, in such a manner that,
while it affords good hold for the wrench employed to screw it on, it gives certain
freedom for the expansion of the metal on each side of the slits as it passes on to
the tapered part of the bolt, the elasticity of the metal so expanded serving to
clamp the bolt and to prevent the nut from unscrewing.
The nuts usually employed are square, hexagonal or octagonal, but the square
form has the advantage of giving convenient hold for the wrench used for screwing
the nut home. I slit such nuts when square across the four sides for about half
their depth from the bottom face, and in order to render the four segments of metal
between the slits capable of yielding sufficiently when the nut passes on to the
larger part of the bolt, I remove part of the metal at each angle so as to allow of
the segment to be bent a little outwards as I will more fully explain referring to
the accompanying drawings.
Fig. 1 is a side view partly in section of a bolt with a nut shewn in section
screwed on it; Fig. 2 is a plan view of the bottom face of a square nut slit across
its four sides, and Figs. 3, 4, 5 and 6 are side and perspective views of the square

page_text: nut sbewing several ways of removing metal from its angles to allow flexure of
the segments between the slits. Fig. 7 is a sectional plan of the nuts shewn in
Figs. 3, 4, 5 an 6 taken at X in these figures.
Referring to Fig. 1, the bolt being made in its front part as from A to B uniformn
in diameter, tapers slightly, as from B to C to a larger diameter in its hinder part.
The nut which is slit for part of its depth by saw cuts forming the slits D, when
it begins to pass on to the tapered part of the bolt, has to expand, the segment<
into which its lower part is divided being thus bent a little outwards. In a square
nut slit across the sides as shewn in Fig. 2; the depth of metal at each angle from a
to b is so considerable that the segments of the nut between the slits do not readily
yield to the taper of the bolt. In order to diminish the resistance of these segments
to flexure, I remove some of the metal from the angles in any of the ways shewn
in Figs. 3, 4, 5, and 7. Thus, as shewn in Fig. 3, a saw-cut c is made in each
angle at a distance from the bottom face about equal to the depth of the slit s. As
shewn in Fig. 4 instead of cutting into the angles with a saw, I cut a rounded
notch d into each angle. As shewn in Fig. 5 the notch is extended down to the
bottom of the nut as a chamfer or flute e; and, as shewn in Fig. 6, the flute fis
extended the whole depth of the nut. Any of these ways of reducing the depth
of metal a to b Fig. 7, may be adopted, as may be best suited to the character of
the machinery employed in making the nuts.
By thus removing metal from the angles, each quarter of the square, from slit to
slit is rendered more capable of being bent a little outwards by the taper of the
bolt, than it would be if the angles of the square were left entire. By removing
the metal in the form of a comparatively narrow but deep flute as shewn in Figs. 6
and 7, enough can be removed to give the desired elasticity without so far trespassing
on the square sides as to make them inconveniently narrow for the application of
the wrench. When the metal is removed by saw cuts, as in Fig. 3, or notches as
in Fig. 4, or by fluted hollows not extending to the upper face of the nut as in
Fig 5, the complete square is left for application of the wrench in the front part
or top of the nut above the slits. The mode of application of my invention to a
hexagonal nut will be readily understood from the above description, on reference
to Fig. 8.
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
In combination with a bolt having its screwed portion or a part thereof tapering
to a larger diameter backwards towards the shank, a nut slit through part of its
depth from the back and having a portion of the metal removed at its angles to
allow flexure of its segments, substantially as and for the purpose herein set forth.
Dated this 2nd day of March 1885
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.