DRILL FOR DEEP HOLE BORING

摘要

PROBLEM TO BE SOLVED: To provide a twist drill capable of boring a deep hole having depth of 15-30 times a drill diameter with non-step. SOLUTION: The twist drill for boring a deep hole is provided with a first web thickness part having web thickness of a blade part of the drill being approximately constant from a tip end side to a base end side; and a second web thickness part. The web thickness of the first web thickness part is larger than that of the second web thickness part and groove surface roughness of the drill is made to 1.5 S or less. A chip discharging property is enhanced by making the web thickness of the first web thickness part and the web thickness of the second web thickness part small by 0.5 to 8% of the drill diameter. COPYRIGHT: (C)2004,JPO