Abstract: A putter head prevents a ball from sliding over a green while maintaining golfers' preferred hitting feel and roll of the ball. A face insert fitted in a face of the putter head has an outer layer which serves as a ball-hitting surface and an inner layer which is located on an inner side of a head body. A smash factor of a second polymer material forming the inner layer is greater than a smash factor of a first polymer material forming the outer layer. Two types of groove, grooves of a first groove group and grooves of a second groove group are formed in an external surface of the outer layer. The grooves of the first groove group may be 0.25 to 1.6 mm wide and 0.05 to 0.5 mm deep and the grooves of the second groove group may be 0.075 to 0.5 mm wide and 0.025 to 0.1 mm deep.

Abstract: This invention provides a hollow golf club head including a fixing member which includes a shaft body formed with a threaded portion at one end, and a head portion at the other end of the shaft body, a viscoelastic body having an opening through which the shaft body extends, a recess portion formed in a circumferential wall of the golf club head and in which the viscoelastic body is disposed, and a screw hole formed in a bottom portion of the recess portion and threadably engages with the threaded portion. The viscoelastic body is fixed between the head portion and the bottom portion by threadably engaging the threaded portion with the screw hole.

Abstract: A golf club head of this invention includes a face, a plurality of score line grooves formed on the face, and a plurality of striations formed on the face. The angle formed by an arrangement direction of the plurality of striations and the score line grooves is between 40 degrees and 70 degrees, inclusive, as viewed clockwise from a toe side end of the score line grooves.

Abstract: This invention provides a golf club head having a first viscoelastic body made of a first viscoelastic material and a second viscoelastic body made of a second viscoelastic material with a loss coefficient the temperature dependence of which is different from that of a loss coefficient of the first viscoelastic material.

Abstract: This invention provides a golf club head comprising a head main body, a face plate fixed to a front surface side of the head main body to form a face surface, a cavity portion formed in the head main body and open to a face plate side, and a viscoelastic body inserted in a compressed state in a space formed by the cavity portion and the face plate. An end face on the face plate side of a circumferential wall defining the cavity portion comprises a contacting portion contacting with a rear surface of the face plate, and a non-contacting portion spaced apart from the rear surface of the face plate to form a gap communicating with the cavity portion between the non-contacting portion and the rear surface of the face plate.

Abstract: A golf head club has a high moment of inertia and thus produces a pleasing hitting sound. A metallic golf club head 1 having a hollow space therein includes a face member 30 provided with a face part 31, and a body member 10 provided with a sole part 11, a crown part 12, a side part 13, and ribs 20. The hollow space is defined by the inner surfaces of the face part 31, the sole part 11, the crown part 12, and the side part 13, and the wall surfaces of the ribs. The ribs 20 extend from the inner surface of the sole part 11 to the inner surface of the crown part 12, and the body member 10 is molded integrally by casting.

Abstract: This invention provides a golf club head including a plurality of score lines on the face. The golf club head includes a plurality of striations formed on the face and extending from a toe side to a heel side. The cross-sectional shape of each of the striations is a triangle asymmetric with regard to a virtual center line in the width direction, and the smallest interior angle among three interior angles of the triangle is placed at the sole side of the golf club head. A depth D from the face to the deepest portion of each of the striation satisfies 10 ?m?D?40 ?m.

Abstract: A golf club head of this invention includes a face, a plurality of score line grooves formed on the face, and a plurality of striations formed on the face. The angle formed by an arrangement direction of the plurality of striations and the score line grooves is between 40 degrees and 70 degrees, inclusive, as viewed clockwise from a toe side end of the score line grooves.

Abstract: This invention provides a method of identifying an antinode of a primary vibration mode of the golf club head having a hollow golf club head having a face portion, a crown portion, a sole portion, and a side portion. A viscoelastic body is to be mounted in at least one of the face portion, crown portion, sole portion, and side portion. The viscoelastic body is mounted in a part of a portion where the viscoelastic body is to be mounted, the part corresponding to an antinode of a primary vibration mode.

Abstract: A hollow golf club head has a face portion, a crown portion, and a sole portion. Assuming that a primary deflection mode frequency of the face portion is Ff, a primary deflection mode frequency of the crown portion is Fc, and a primary deflection mode frequency of the sole portion is Fs, the Ff, Fc and Fs satisfy the following expressions: 3000 Hz<Ff<4000 Hz; 3000 Hz<Fc<4000 Hz; Fs>4000 Hz. The face portion, the crown portion and the sole portion have no mode frequency of 3000 Hz or less.

Abstract: This invention provides a golf club head having a viscoelastic body, wherein the viscoelastic body is made by mixing a plurality of types of viscoelastic materials with loss coefficients temperature dependences of which are different.

Abstract: A wood club head having a loft angle of not less than 13° is provided. The hosel length is not less than 20 mm. The face progression is set to fall within a range of 12 mm to 16 mm (both exclusive). The barycenter depth is set to fall within a range of 20 mm to 25 mm (both exclusive).

Abstract: The sole shape can be designed with ease. The invention provides a method for designing an iron sole shape that includes the steps of setting different parameter values (S1) relating to a sole shape while keeping parameters other than those of the sole shape constant, preparing an iron club (S2) having the parameter values that have been set, a tester using the iron club that has been prepared to hit a ball (S4), measuring a path of the club head (S5) using a camera to obtain data relating to a position and a velocity of the club head, and determining whether or not the sole shape is favorable (S6) based on the data that have been obtained.

Abstract: This invention provides a golf club head including a plurality of score lines on the face. In the golf club head according to this invention, the score line includes a pair of side surfaces and a bottom portion having a protruding portion protruding toward the face. An angle between the side surface and the face is not less than 60 degrees. A cross-sectional area A (inch2) of the score line, a width W (inch) of the score line measured based on the 30 degrees measurement method, and a distance S (inch) between the score lines adjacent to one another satisfy A/(W+S)?0.003.

Abstract: This invention provides a wood type golf club including a shaft, a grip at one end of the shaft, and a head at the other end of the shaft, wherein a mass m (g) of the golf club and a length L (cm) from a grip side end of the golf club to a barycentric position of the golf club satisfy m×L=2.55×104 (g·cm) and m×L2=2.322×106 (g·cm2), and a barycentric position of the shaft is at 48.3% a total length of the shaft from a head side end of the shaft.

Abstract: This invention provides a golf club head including a plurality of score lines on a face. In the golf club head according to this invention, the angle between each side surface of the score lines and the face is 48° or more. Edges of the score lines are formed to be positioned within a second virtual circle with a radius of 0.011 inches, the second virtual circle being concentric with a first virtual circle which internally touches the side surface of the score line and the face with a radius of 0.010 inches.

Abstract: This invention provides a golf club head including a plurality of score lines on a face. In the golf club head according to this invention, the angle between each side surface of the score lines and the face is 48° or more. Edges of the score lines are formed to be positioned within a second virtual circle with a radius of 0.011 inches, the second virtual circle being concentric with a first virtual circle which internally touches the side surface of the score line and the face with a radius of 0.010 inches.