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: This invention provides an improved hollow golf club head having a sole portion and a crown portion, wherein the golf club head is configured so as to increase the launch angle of a ball so that the traveling distance of a golf shot can be increased. In particular, the sole portion and the crown portion of the hollow golf club head are configured such that the ratio of a rigidity of the sole portion to a rigidity of the crown portion is 1:0.1 to 0.8 and, as a result of such a configuration, the launch angle of a hit ball is increased.

Abstract: A golf club head has a face portion with a thick-walled portion located in the center of the face portion and an outer peripheral portion located on an outer periphery of the thick-walled portion. The thick-walled portion has a central portion of the face portion having a largest thickness, a first ridge which surrounds the central portion and has a smaller thickness than the central portion, and a first valley which is located between the central portion and the first ridge and has a smaller thickness than the first ridge. The golf club head maintains a low weight of a face portion and suppresses dispersion of CT values at each hitting point so that the CT values at hitting points other than a sweet spot are substantially equal to the CT value at the sweet spot.

Abstract: A method for replacing a shaft of a golf club, the golf club including: a head having a hosel; the shaft; a shaft case fixed to one end of the shaft, and configured to be inserted into the hosel; and a ring-shaped screw member configured to be screwed into one end of the hosel to fix the shaft case in the hosel, and to be fitted with an outer face of an one end of the shaft case, the ring-shaped screw member being noncontact with the shaft, the method comprising: fixing a newly-provided shaft to a newly-provided shaft case corresponding to the hosel; unscrewing the ring-shaped screw member from the hosel; removing the shaft case with the shaft from the hosel; inserting the newly-provided shaft case with the newly-provided shaft to the hosel; and screwing the ring shaped screw member on the hosel.

Abstract: A face portion of a golf club head includes first to fourth main ribs on an inner surface of the head. The first main rib extends from a center portion of the face portion toward a crown, and the second main rib extends from the center portion toward a sole. The face portion is formed to have such a thickness that the center portion, the first main rib, and the second main rib become thinner in this order. The third and fourth main ribs extend from the center portion in outward directions of the face portion.

Abstract: A hollow golf club head has a head body having a face aperture part and a face member held to the face aperture part by welding, the face member formed by forging a rolled material of a titanium alloy having an ? phase, and the face member comprising a thick-material part positioned in the center of the face member, an outer peripheral part positioned at the periphery of the thick-material part, and a thin-material part partially positioned between the thick-material part and the outer peripheral part. The thick-material part is formed in an area having a shape obtained by depressing a substantially elliptical or substantially circular shape in a substantially arcuate shape toward the center of the ellipse at two opposite sides thereof. The thick-material part, the thin-material part, and the peripheral part are formed by the forging so as to destroy an orientation of the ?-phase.

Abstract: According to an aspect of the invention, a golf club includes: a head having a hosel; a shaft; a shaft case fixed to one end of the shaft, and configured to be inserted into the hosel, the shaft case being formed in a substantially cylindrical shape; and a ring-shaped screw member configured to be screwed into one end of the hosel to fix the shaft case in the hosel, and to be fitted with an outer face of an one end of the shaft case, the ring-shaped screw member being noncontact with the shaft.

Abstract: A hollow golf club head according to this invention includes a face portion, a crown portion, a sole portion, and a side portion. This golf club head includes a head body that forms the crown portion, the sole portion, and the side portion and has an opening portion in a portion corresponding to the face portion, and a face member that is joined to the opening portion and forms the face portion. The head body includes a first notch portion formed in a heel-side portion of the peripheral edge of the opening portion, which is on the side of the crown portion, and a second notch portion formed in a toe-side portion of the peripheral edge, which is on the side of the sole portion. The face member includes a first extending portion that seals the first notch portion, and a second extending portion that seals the second notch portion.

Abstract: A golf club head includes: a head main body formed with a hosel column inserting hole; a hosel column which is formed with a shaft inserting hole and is installed on the hosel column inserting hole; a bolt inserting hole penetrating from a sole side of the head main body to the hosel column inserting hole; and a bolt which is inserted into the bolt inserting hole and is screwed into the hosel column, wherein: the hosel column includes a trunk portion provided with a shaft inserting hole, and a leg portion which protrudes from a lower end surface of the trunk portion and is inserted into the hosel column inserting hole; and at least a lower end side of the leg portion and an inner portion of the hosel column inserting hole are polygonal sectional shape portions and are engaged with each other.

Abstract: A golf club head includes: a head main body having a shaft holder inserting hole; a shaft holder which has a shaft inserting hole and is attachably and detachably installed in the shaft holder inserting hole; a bolt inserting hole which penetrates from a sole side of the head main body to the shaft holder inserting hole; and a bolt which is inserted into the bolt inserting hole, screwed into the shaft holder, and fixes the shaft holder to the head main body, an axis center of the shaft inserting hole and an axis center of the shaft holder inserting hole being non-coaxial shapes, wherein a lower end side of the shaft holder and an inner portion of the shaft holder inserting hole are polygonal sectional shape portions and are engaged with each other.

Abstract: A golf club head 1 has a face part 2, a crown part 3, a sole part 4, a side part 5, and a hosel part 6, which are formed of titanium or a titanium alloy. The golf club head 1 is formed by integrating a head body 10 and a face plate 30 with each other by welding such as laser welding or plasma welding. A thick part 20 is provided only in the central portion in the toe-heel direction of the cross corner portion between the face part 2 and the sole part 4. The width in the toe-heel direction of the thick part 20 is 20 mm or narrower. Therefore, the golf club head in accordance with the present invention can increase a carry on average even if being used by an amateur golfer who is prone to hit a ball by varied hit points across the clubface.

Abstract: A golf club head includes a face member having a ball-striking face and an oval thick portion positioned in a central portion of the ball-striking face. The oval thick portion has an oval shape having recesses formed by recessing both sides in a major axis direction in an arc-shaped fashion. The recesses are directed to a toe-side upper portion and a heel-side lower portion. The thickness of the thick portion becomes thickest at a central portion and is gradually reduced from the central portion towards the periphery. The face member is formed such that a portion outside the thick portion is thinner than the thick portion. An occupancy rate of the oval thick portion in the ball-striking face is in a range of 25 to 45%.

Abstract: A golf club head according to this invention includes a hollow head body, cylindrical body, weight member, and fixing member. The hollow head body has a projection formed along the periphery of the sole, a recess formed inside the projection, and an opening formed in the projection so as to extend from the toe side to the back side. The cylindrical body is provided in the recess of the head body, and includes its one end which engages with the inner wall of the projection on the heel side, and its other end which extends to the vicinity of the opening and can move along the opening. The weight member is retractably, detachably inserted in the cylindrical body. The fixing member is a detachable member which fixes the other end of the cylindrical body onto the projection.

Abstract: A hollow golf club head includes a head main body having a face opening portion on a face side, and a face member that closes the face opening portion. A part or all of an upper edge of the face opening portion and an upper edge of the face member extends to a crown portion.

Abstract: There is provided a golf club head capable of increasing carry on average even if being used by an amateur golfer who is prone to hit a ball with various hit points across the clubface. A golf club head 1 has a face part 2, a crown part 3, a sole part 4, a side part 5, and a hosel part 6, which are formed of titanium or a titanium alloy. The golf club head 1 is formed by integrating a head body 10 and a face plate 30 with each other by welding such as laser welding or plasma welding. A thick part 20 is provided only in the central portion in the toe-heel direction of the cross corner portion between the face part 2 and the sole part 4. The width in the toe-heel direction of the thick part 20 is 20 mm or narrower.

Abstract: A golf club head includes a face member having a ball-striking face and an oval thick portion positioned in a central portion of the ball-striking face. The oval thick portion has an oval shape having recesses formed by recessing both sides in a major axis direction in an arc-shaped fashion. The recesses are directed to a toe-side upper portion and a heel-side lower portion. The thickness of the thick portion becomes thickest at a central portion and is gradually reduced from the central portion towards the periphery. The face member is formed such that a portion outside the thick portion is thinner than the thick portion. An occupancy rate of the oval thick portion in the ball-striking face is in a range of 25 to 45%.

Abstract: A golf club head includes a hollow head main body provided with a recess portion in a sole portion thereof; a gravity center characteristic adjusting portion with a plate shape disposed in the recess portion between a center part of the recess portion and a part of a surrounding wall of the recess portion; and a fixing portion for fixing the gravity center characteristic adjusting portion onto the hollow head main body at an arbitrary rotational position.

Abstract: A golf club head according to this invention includes a hollow head body, cylindrical body, weight member, and fixing member. The hollow head body has a projection formed along the periphery of the sole, a recess formed inside the projection, and an opening formed in the projection so as to extend from the toe side to the back side. The cylindrical body is provided in the recess of the head body, and includes its one end which engages with the inner wall of the projection on the heel side, and its other end which extends to the vicinity of the opening and can move along the opening. The weight member is retractably, detachably inserted in the cylindrical body. The fixing member is a detachable member which fixes the other end of the cylindrical body onto the projection.

Abstract: A golf club includes: a head, formed with a hosel insertion hole, including: a female screw, formed in an inner peripheral surface of the entrance portion of the hosel insertion hole; a hosel, formed with a shaft case insertion hole and mounted on a deep portion of the hosel insertion hole; a shaft case, formed with a shaft insertion hole, a leading end portion of the shaft case being mounted into the shaft case insertion hole; a ring holder, fitted with an outer surface of the shaft case; a screw member, fitted with an outer surface of the ring holder in a peripheral direction of the ring holder; and a male screw, formed on an outer peripheral surface of the screw member so that the screw member is engaged with the female screw; and a shaft, inserted into the shaft insertion hole of the head.

Abstract: A golf club head with a leading end of a shaft mountable thereon, the golf club head includes: a head main body, formed with a hosel insertion hole; a hosel, formed with a shaft case insertion hole and removably mounted in the hosel insertion hole; and a shaft case, formed with a shaft insertion hole and removably mounted in the shaft case insertion hole.