In the accompanying drawings, the screw driver shank 1
is threaded at its outer end and the portion 2 projecting
beyond the thread 3 is slotted longitudinally through
the center to receive the bit holder 4 which is in the
form of a U-shaped member preferably formed of hardened
steel and having the outer sides 5 of its ends bevelled
and the inner sides chamfered at 6.
The holder 4 fits snugly into the slot 7 and a chuck
sleeve 8 internally threaded at its inner end to engage
the thread 3 holds the bit holder securely in place.
The sleeve 8 is formed with an inwardly bevelled surface
9 at its outward end to engage the beveled surfaces
5 of the bit holder to squeeze them inwardly to bind
the bits in position when placed therein side by side.
The bits 10 are formed of square bars of tool steel
each having one end reduced to form the narrow screw
driver extremity 11. These are suitably tapered so that
they will fit a comparatively small screw but will be
strong enough to enter the deeper slots of a larger
screw and to effectively turn it.
The opposite ends of the bits may be square for use
with socket type screws.
The bits are placed together in the holder 4 with the
slot engaging ends arranged in alignment and with the
three bits thus placed as shown in Figure 1, and 5 the
screw driver will engage successfully with a heavy slotted
It will be noted that the outer bits 10 as shown in
Figures 1 and 5 are arranged with their outer slot-engaging
ends in alignment and that the extreme inner ends thereof
engage the top of the stud 12 to support the bits in
their extended aligned position. These outer bits are
each provided with a notch or offset 10' at the inner
end so that when it is desired to lower either of said
side bits, the latter are removed and turned half a
turn so that the offset end formed by the notch 10'
will pass the stud which is slightly wider than any
of the bits, thus retreating further into the chuck
or holder leaving the remaining bit or bits supported
in extended working position. In this way, by manipulating
the outer bits, the effective width of the slot-engaging
or working end of the screw driver may be varied in
accordance with requirements from the maximum three
blade width to the medium and minimum two and one blade
When the tool is to be used with tubular spoke screws
the offset ends may be arranged in the outward position
to provide a slightly wider space in the center, as
shown in Figure 3.
It will be noted that as the ends 6 of the holder 4
are chamfered, the placing and removing of the bits
in the holder will be rendered very simple.
I have shown the invention applied to a hand operated
screw driver but it will be understood the chuck end
can be provided with a drill holder handle or the handle
of a brace.