Combined drill and reamer

Claim 1

A combined drill and reamer tool, comprising: a cylindrical body having a longitudinally extending axis of rotation, said body including a twist drill part for drilling, and a spiral reamer part for finishing, a hole in a workpiece having a thickness less than the respective longitudinal lengths of said twist drill part and said spiral reamer part, and a shank part for being held by the chuck of a rotary drill, said twist drill part being formed at one longitudinal end of said body, said shank part being formed at the other longitudinal end of said body, and said spiral reamer part being formed between said shank part and said twist drill part; said twist drill part having; a free tip end having a straight chisel edge and first and second radial drill cutting edges extending generally radially from opposite ends of said chisel edge to the radial periphery of said free tip end, an other end of said twist drill part, opposite said free tip end, and first and second twist drill cutting edges, respectively extending helically in a first circumferential direction at a same first helix angle with respect to said axis, from said first and second drill cutting edges at the radial periphery of said free tip end to said other end of said twist drill part; said twist drill part and said spiral reamer part having first and second twist drill flutes for passing therethrough chips of a workpiece cut away by said combined drill and reamer tool upon rotative application of said tool by the drill to the workpiece, respectively extending spaced from, parallel to and along the full extent of said first and second twist drill cutting edges, and a first drill twist land between said first twist drill cutting edge and said first twist drill flute and a second twist drill land between said second twist drill cutting edge and said second twist drill flute, said first twist drill flute and said first land, and said second twist drill flute and said second land, respectively continuing longitudinally beyond said first and second twist drill cutting edges at said first helix angle through said spiral reamer part; said spiral reamer part having; a front neck of short longitudinal length adjacent said other end of said twist drill part, a plurality of spiral reamer cutting edges, each spiraling on and extending completely across said first and second drill twist lands from said front neck to said shaft part around said axis in a circumferential direction opposite said first circumferential direction at a second helix angle with respect to said axis in the range 40° to 65°, a chamfer of short longitudinal length adjacent said front neck, for facilitating said plurality of spiral reamer cutting edges biting into the workpiece, a plurality of spiral reamer flutes formed in said first and second drill twist lands spaced from and extending parallel to respective ones of said plurality of spiral reamer cutting edges so as to spiral about said axis at said second helix angle for providing passages opening into said first and second twist drill flutes for passing therethrough into said first and second twist drill flutes chips of the workpiece cut away by said plurality of spiral reamer a plurality of spiral reamer lands bridging the respective spaces between each of said plurality of spiral reamer cutting edges and said respective ones of said plurality of spiral reamer flutes, on each of said first and second twist drill lands, and a rear neck of short longitudinal length adjacent said shank part.