Importance

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Abstract

A head 2 has a face line 8 having a depth of D1 (mm). In a section line of a surface of the face line 8, a boundary between a land area LA and the face line 8 is defined as a point Pa; a point of which a depth is [D¼] (mm) is defined as a point Pb; a point of which a depth is [D½] (mm) is defined as a point Pc; a point of which a depth is [(D1)×(¾)] (mm) is defined as a point Pd; a radius of a circle CL1 passing through three points of the point Pa, the point Pb, and the point Pc is defined as R3 (mm); a straight line passing through the point Pc and the point Pd is defined as a straight line Lcd; a straight line perpendicular to the land area LA is defined as a straight line Lp; and an angle between the straight line Lcd and the straight line Lp is defined as θm. At that time, the radius R3 is 0.01 (mm) or greater and 0.10 (mm) or less, and the angle θm is 40 degrees or greater and 70 degrees or less.

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First Claim