DRILL

PROBLEM TO BE SOLVED: To provide a drill excellent in the chip discharging property for deep hole machining, not changing the groove width and spiral angle of a helical flute at the tip after a cutting edge is reproduced by regrinding, and exerting stable performance. SOLUTION: This drill is provided with a helical flute 6 having the constant groove width and constant spiral angle respectively at a drill tip section 1, and it is provided with a helical flute having the larger and constant groove width and smaller and constant spiral angle than those of the helical flute 6 at the drill tip section 1 at a drill rear section 3. The groove width and spiral angle of the helical flute are gradually changed at a drill middle section 2 between the drill tip section 1 and drill rear section 3.