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 screw.

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 widths respectively.

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.