Title: Gun drill

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Abstract: A gun drill for forming a hole in a metal workpiece consisting of a generally cylindrical body having a shank portion and a tip portion. The body has a longitudinally extending groove formed in its outer surface which extends the full length of the tip portion, and the terminal end of the tip portion has a single cutting edge which extends radially through the axis of the tip portion adjacent the terminal end of the groove. The tip portion is formed intermediate its ends with a wall section located to one side of the groove and in substantial alignment with the cutting edge in a direction longitudinally of the body. A pair of fluid passages are formed in the body, one terminating at the wall section in an orifice directed toward the cutting edge, and the other terminating in an orifice located in the terminal end of the tip portion in a spaced relation with the cutting edge. Fluid discharged through the orifices acts to flush metal chips removed from the workpiece by the cutting edge into the groove for reverse flow out of the hole being drilled. An inclined surface is formed on the tip portion extending in a direction axially of the drill from the wall section rearwardly toward the shank portion to further facilitate fluid flow and chip flushing at the tip portion of the drill.


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