Combination screw-tapping and screwdriving tool

Claim 1

A drill bitholder, said holder being a hexagonal rod with a cylindrical aperture running longitudinally down the center, a slot running longitudinally the length of the holder and extending radially from the center aperture to the outside hexagonal surface, said holder having at one end a conical tip with an abrasive cutting means, said central cylindrical aperture corresponding in diameter to specific drill bit sizes recommended for the drilling of pilot holes for specific screw sizes, whereby the corresponding drill bit is inserted through the aperture of the bitholder to a desired depth relative to the conical end of the bitholder, the conical end being the frontal end with the bit extending from it outward to the bit tip, said depth determined by the desired pilot hole depth, whereupon the drill bitholder is engaged distal end first in the chuck of a drill for up to two-thrids its length, and upon tightening of the chuck, the inward pressure of the chuck forces the bitholder to contract radially against the drill bit, holding it firmly in place, said assembly ready for drilling a pilot hole to a preferred shape, said shape corresponding in whole or in part to the embodiments of the bit and bitholder assembly, said embodiments being the cylindrical shaft of the bit, the conical flared end of the bitholder, and the enlarged cylindrical shape produced by the hexagonal bitholder in rotation, said pilot hole shape determined by the depth with which the tool is forced into the workpiece to produce the desired hole for simple flush-mounting, countersinking, or counterboring of various screw types.