Improvements in Screw Drivers.
Year: 1888

page_text: Date of Application, 21st Jan., 1888
Specification Accepted, 24th Feb., 1888
Improvements in Screw Drivers.
I, DANIEL ROBERTSON HART of 112 East Twenty Seventh Street in the City and
State of New York, United States of America, tram car builder, do hereby declare
the nature of my invention for "IMPROVEMENTS IN SCREW DRIVERS," and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-―
My invention relates to a screw driver for inserting screws of the character herein-
after mentioned in wood and other material, and it consists in a novel construction
of such tool whereby I am enabled to insert said screws much more easily and
effectively than has heretofore been done.
Considerable difficulty has been experienced by mechanics and others in inserting
said screws by the use of the ordinary screw driver. After considerable thought and
experiment, I have found the cause of the said difficulty, and have also invented
means by which it is avoided.
In manufacturing the screw with which I am acquainted and to which my invention
pertains, and which screw is intended more particularly for use in wood, one of the
steps is to mill the head of the screw so as to form a slot or nick therein to allow of
the insertion of the driver. I have discovered that the result of the milling is, among
other things, to make the bottom of the slot of a concave form by reason of the
circular form of the milling cutter, so that when the ordinary screw driver is inserted
in the slot, such driver which is straight at the point, instead of bearing against the
whole length of the bottom of the slot, bears only upon the extremities thereof.
Another defect in the said driver is the tapering or wedge-shaped form of those
portions of the sides thereof which enter the slot of the screw head.
In practice serious consequences follow the use of such driver on said screws. For
example, when the driver is forced against the screw it tends to spread or split the
head thereof, for the reason that the driver's wedge-shaped form tends to prevent its
insertion sufficiently to touch the lower portion of the walls of the slot, and, therefore,
causes it to act upon the upper portion of said walls, and thereby give a ragged and
uneven appearance to the slot. More particularly is this the case when the screws
have been highly finished or plated. Besides, the said wedge-shaped point of the
driver will tend to cause it to rise out of, the slot when pressure is applied to turn the

page_text: screw. Another difficulty with the ordinary screw driver in inserting the aforesaid
screws is its tendency to slip from the slot sidewise, especially when the screw is in
such a position, as, for instance, in a corner, that the operator is required to hold the
screw driver at an angle or out of alignment with the screw.
My invention has for its object the obviation of the difficulties mentioned, and it
consists, first, in constructing the bottom of the screw driver in such form that when
fully inserted in the slot of the screw-head it will bear against all parts of the bottom
of the slot, and, secondly, in making those portions of the sides of the screw driver
which enter the slot of the screw head slightly tapering, being thickest at the point,
by the use of which said invention the operator is enabled to easily and effectively
insert the aforesaid screws wherever desired.
In the drawings, Fig. 1 represents a front view of a hand screw-driver constructed
according to my invention. Fig. 2 is a side view of a portion of the same. Fig. 3 is
a front view of a screw-driver bit adapted to be used in a bit-stock; and Fig. 4 is a
side view of one of said screws for use in wood, a portion being broken away to show
the slot.
a, designates one of said screws for use in wood, having a head portion, b, provided
with a slot, c, to receive the screw driver. d, is a screw driver, provided with.a
handle, e, and having its point, f, made in convex form, so as to correspond with and
fit upon the concave or arc-shaped bottom of the slot, c. The sides of that portion of
the screw driver which engages with the slot are made to taper slightly in thickness
from the point, f, having less thickness at the part 9 than at the point, f. By this
construction the screw driver when inserted in the slot, c, will act on the lower or
base portion of the walls of the slot, thereby preserving the upper and exposed edges
of the slot from injury while inserting the screw.
By my invention a screw driver while inserting one of said screws cannot slip out
of the slot, since the concave form of the bottom of the latter prevents the point, ƒ,
moving sidewise in the slot when pressure is applied to turn the screw.
A screw
driver forined with tapering sides, as described, will be prevented from rising in
the slot when pressure is applied to turn it, and will also act on the lower portions
of the walls of the slot, thus preserving the exposed edges thereof and avoiding
spreading or splitting the head of the screw.
My invention is applicable to screw drivers adapted to operate on said screws
having counter-sunk, oval or other shaped heads.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. A screw-driver having its point or front end made in convex form to
correspond with and fit the concave form of the bottoms of screw head slots, sub-
stantially as described.
2. A screw driver having its point or front end made in convex form to correspond
with and fit the concave form of the bottoms of screw head slots, and having those
portions of its sides adapted for entering said slots, tapering in thickness, substantially
as described.