Year: 1887

page_text: I, LEONARD EDWIN SUNTER of 18 Carlisle Street Lambeth, in the County of
Surrey, Engineer do hereby declare the nature of this invention to be as follows:-
.
My invention relates to screws and screw-drivers and consists partly in making a
specially shaped nick or slot in the head of a screw and partly in providing a screw-
driver of special construction for use with screws having such nicks or slots.
According to my said invention, I form the nick or slot in such manner that the
base of the same is wider than the upper part or entrance thereof that is to say the
shape of the nick or aperture is triangular or dovetail in transverse section
the opening being (at the surface of the head) of the same or about the same
width as the nick of an ordinary screw and widening out on both sides in a
downward direction. I prefer that the bottom of this nick or aperture shall be
somewhat rounded on both sides, but this is not essential.
The object of providing the heads of screws with this dovetail or triangular nick
is that a more secure hold may be obtained for driving the screw into the metal or
other substance or material in which it is to be used; and in order that the whole
advantage of this formation may be obtained I provide a special screw-driver or tool
the end of which is made triangular or dovetail so as to fit the nicks or slots made as
above described. These screw drivers may be made with ordinary handles and the
triangular end will (when required to be used) be inserted in the nick laterally, the
handle projecting vertically above the head of the screw. In some cases this tool or
driver may be so made that when the triangular end is inserted in the nick the handle
will project horizontally from the side of the screw-head. I may also provide the
said driver with a lug or piece designed to lie along one side of the head of square
headed screws so that the turning of the screw may thereby be facilitated, this
arrangement being particularly useful for screws of large dimensions.
[Di 17

page_text: My invention is designed chiefly for use with machine-screws, that is to say screws
employed in securing together metal work of various kinds but it may also be used
advantageously with wood screws, especially those of the larger kinds.
Although I have described a special driver or tool for use with these screws it is
obvious that an ordinary screw driver may be employed if desired.

page_text: or slot, the said screw-driver c has a triangular end or part d so shaped that it will
fit loosely in the groove or slot b of the screw shown in Figures 1 and 2, and in
the grooves or slots of various other sized screws.
In using this improved screw-driver c, the triangular end or part d is inserted
laterally in the groove or slot 6 in the head of the screw, the handle of the
screw-driver projecting vertically above the head a¹ of the said screw.
The screw-driver can then be turned without liability to slipping of the same out
of the groove or slot in the screw.
In some cases I employ a screw-driver e (Figure 5) so constructed that, when
the triangular end or part is inserted in the groove or slot b, the handle will
project horizontally from the side of the screw-head. The said screw-driver is
sometimes provided with lugs or pieces g, designed to engage with one side of the
head of the screw to facilitate the turning of the said screw. This arrangement is
particularly useful for screws of large dimensions.
o
When the heads of the screws are intended to be countersunk either in wood or
metal, the groove or slot is undercut on one side only.
Figure 6 is a portion of a wood-screw with a head
above described and having a semi-dovetail groove or slot i.
intended to be countersunk as
Figure 7 is a cheese-headed machine-screw with a head k intended to be counter-
sunk and with a semi-dovetail groove or slot l. This semi-dovetail form of groove
or slot permits, by using a screw-driver m Figure 8 having a corresponding semi-
dovetail projection n, of withdrawing the said screw-driver m from the groove or
slot i or when the head h or k of the screw is driven home in the countersink or let
in flush with the metal or wood.
Although for the purpose of illustrating my said invention I have hereinbefore
described and illustrated a machine-screw having a cheese-head and a wood-screw
with a common countersink head, it is obvious that my said invention can be advan-
tageously applied to screws, for either metal or wood, of any shape or form adapted
to bo driven by a screw-driver.
Either the special screw-drivers above described can be employed with my improved
screws, or any ordinary screw-driver.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I wish it understood
that I claim :-
First. A screw having the groove or slot in the head thereof undercut on one or
both sides, substantially as, and for the purpose, set forth.
Second. A screw-driver having an enlargement at the end thereof adapted to fit
the undercut grooves or slots in the heads of my improved screws, substantially as,
and for the purpose, set forth.
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amba 1907