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1. (WO2017179689) SMALL-DIAMETER DRILL BIT

Pub. No.:    WO/2017/179689    International Application No.:    PCT/JP2017/015260
Publication Date: Fri Oct 20 01:59:59 CEST 2017 International Filing Date: Sat Apr 15 01:59:59 CEST 2017
IPC: B23B 51/00
Applicants: MITSUBISHI HITACHI TOOL ENGINEERING, LTD.
三菱日立ツール株式会社
Inventors: YOSHIOKA Shogo
吉岡 尚吾
Title: SMALL-DIAMETER DRILL BIT
Abstract:
In the case of this small-diameter drill bit, two cutting blades (7) having main cutting blades (7a), the lengths (W) of which differ from each other by 0.04 mm or less, are formed on the tip of a double-margin drill bit body (1) which has a diameter of 2 mm or less and a margin length/diameter ratio of 3 or more. In terms of the relationship between two tip flank faces (5), a first extension line (N1) extending from one of linear first intersecting ridgelines (M1), which is formed by a first tip flank face (5a) and a second tip flank face (5b) of one of the flank faces, into the other flank face is positioned on the leading side in the drill bit rotation direction (T) with respect to the other linear first intersecting ridgeline (M1), wherein the distance (d1) between the first extension line and the linear first intersecting ridgeline is in a range of 0.04 mm-0.08 mm. In addition, a second extension line (N2) extending from one of linear second intersecting ridgelines (M2), which is formed by the second tip flank face (5b) and a thinning face (8a) of the one flank face, into the other flank face is positioned either in a straight line with the other linear second intersecting ridgeline (M2) or on the leading side in the drill bit rotation direction (T) with respect to the other linear second intersecting ridgeline (M2), wherein the distance (d2) between the second extension line and the linear second intersecting ridgeline is in a range of 0.08 mm or less.