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1. (WO2017034038) DRILL

Pub. No.:    WO/2017/034038    International Application No.:    PCT/JP2016/075153
Publication Date: Fri Mar 03 00:59:59 CET 2017 International Filing Date: Tue Aug 30 01:59:59 CEST 2016
IPC: B23B 51/00
B23B 51/06
Applicants: MITSUBISHI MATERIALS CORPORATION
三菱マテリアル株式会社
Inventors: YAMAMOTO Tadashi
山本 匡
YANAGIDA Kazuya
柳田 一也
TSURUMAKI Yuya
弦卷 優矢
Title: DRILL
Abstract:
Thinning rake faces (6a) are formed on the tip part of a drill bit body (1) rotating about an axis (O) such that intersecting edge lines of the thinning rake faces with tip flank faces (2) form thinning cutting edges (4a), and first thinning wall faces (6b) continuous with thinning rake faces (6a) and second thinning wall faces (6c) continuous with the first thinning wall faces (6b) are formed on the opposite side of chip discharge grooves (3) to the drill rotation direction (T). When looked at from the tip side in the axial direction (O), the intersecting angle of each thinning cutting edge (4a) with a first thinning edge line (L1) is larger than 95 degrees, a second thinning edge line (L2) is bent opposite to the drill rotation direction (T) with respect to the first thinning edge line (L1), the thinning cutting edge (4a) and the first thinning edge line (L1) are continuous with each other via a concave curved line (N1), the first and second thinning wall faces (6b, 6c) are continuous with each other via a concave curved face, and the curvature radius (R1) of the concave curved line (N1) is smaller than the curvature radius (R2) of the concave curved face.