Abstract: A golf ball which comprises a spherical core and a cover, wherein the cover has a nominal thickness of 0.1 mm to 1.2 mm. Dimples are formed on the surface of the cover and concave portions are formed on the surface of the core, the position of the concave portions corresponding to that of the dimples. The golf ball is obtained by forming the core by means of a mold having a large number of projections provided on a cavity surface thereof. By the projections, the concave portion is formed. When the cover is to be formed, the position of the core is determined in such a manner that the projections for forming the dimple correspond to the concave portions.

Abstract: A ball motion measuring apparatus comprises a tee 3 for mounting a golf ball 1 thereon, a first camera 5, a second camera 7, a pair of first stroboscopes 9, a pair of second stroboscopes 11, a pair of optical sensors 13, a CPU 15 to be a calculating section, and a monitor 17 to be a display section. The first camera 5 and the second camera 7 are CCD cameras having a shutter function. Photographing is carried out by means of the first camera 5 after a predetermined time passes since the golf ball 1 is hit, and the photographing is carried out by means of the second camera 7 after a predetermined time further passes. A magnified image is formed by original image data thus obtained and a read value obtained by pointing the magnified image is subjected to distortion correction or oblique correction so that correction data are obtained. Based on the correction data, a flight speed, a spin rate or a launch angle of the golf ball 1 is calculated.

Abstract: A golf ball including a spherical core and a cover. The cover has a nominal thickness of 0.1 mm to 1.2 mm. A dimple is formed on the surface of the cover. A concave portion is formed on the surface of the core. The position of the concave portion corresponds to that of the dimple. The golf ball is obtained by forming the core by means of a mold having a large number of projections provided on a cavity surface thereof. By the projections, the concave portion is formed. When the cover is to be formed, the position of the core is determined in such a manner that the projections for forming the dimple correspond to the concave portions.

Abstract: A golf ball (1) comprises a spherical core (2) and a cover (3). The cover (3) has a nominal thickness of 0.1 mm to 1.2 mm. A dimple (4) is formed on the surface of the cover (3). A concave portion (6) is formed on the surface of the core (2). The position of the concave portion (6) corresponds to that of the dimple (4). The golf ball (1) is obtained by forming the core (2) by means of a mold having a large number of projections provided on a cavity surface thereof. By the projections, the concave portion (6) is formed. When the cover (3) is to be formed, the position of the core (2) is determined in such a manner that the projections for forming the dimple (4) correspond to the concave portions (6).

Abstract: Dimple 4 has a side wall curved face 8 and an edge neighboring curved face 9. The side wall curved face 8 is situated between a point P4 positioned downward from the dimple edge Ed by the depth of 20% in an in-depth direction and a point P3 positioned downward from the dimple edge Ed by the depth of 50% in an in-depth direction. The edge neighboring curved face 9 is situated between the dimple edge Ed and a point P5 positioned downward from the dimple edge Ed by the depth of 10% in an in-depth direction. Proportion of the number NL of dimples 4 having the diameter of equal to or greater than 3.90 mm occupied in total number N of the dimples is equal to or greater than 75%. Proportion of the number ML of dimples having the ratio (Re/Rw) between a radius of curvature of Re of the edge neighboring curved face 9 and a radius of curvature Rw of the side wall curved face 8 of 0.5 or greater and 1.5 or less of equal to or greater than 75%, having the diameter of equal to or greater than 3.

Abstract: Dimple 4 has a side wall curved face 8 and an edge neighboring curved face 9. The side wall curved face 8 is situated between a point P4 positioned downward from the dimple edge Ed by the depth of 20% in an in-depth direction and a point P3 positioned downward from the dimple edge Ed by the depth of 50% in an in-depth direction. The edge neighboring curved face 9 is situated between the dimple edge Ed and a point P5 positioned downward from the dimple edge Ed by the depth of 10% in an in-depth direction. Proportion of the number NL of dimples 4 having the diameter of equal to or greater than 3.90 mm occupied in total number N of the dimples is equal to or greater than 75%. Proportion of the number ML of dimples having the ratio (Re/Rw) between a radius of curvature of Re of the edge neighboring curved face 9 and a radius of curvature Rw of the side wall curved face 8 of 0.5 or greater and 1.5 or less of equal to or greater than 75%, having the diameter of equal to or greater than 3.

Abstract: A golf ball (1) comprises a spherical core (2) and a cover (3). The cover (3) has a nominal thickness of 0.1 mm to 1.2 mm. A dimple (4) is formed on the surface of the cover (3). A concave portion (6) is formed on the surface of the core (2). The position of the concave portion (6) corresponds to that of the dimple (4). The golf ball (1) is obtained by forming the core (2) by means of a mold having a large number of projections provided on a cavity surface thereof. By the projections, the concave portion (6) is formed. When the cover (3) is to be formed, the position of the core (2) is determined in such a manner that the projections for forming the dimple (4) correspond to the concave portions (6).

Abstract: A ball motion measuring apparatus comprises a tee 3 for mounting a golf ball 1 thereon, a first camera 5, a second camera 7, a pair of first stroboscopes 9, a pair of second stroboscopes 11, a pair of optical sensors 13, a CPU 15 to be a calculating section, and a monitor 17 to be a display section. The first camera 5 and the second camera 7 are CCD cameras having a shutter function. Photographing is carried out by means of the first camera 5 after a predetermined time passes since the golf ball 1 is hit, and the photographing is carried out by means of the second camera 7 after a predetermined time further passes. A magnified image is formed by original image data thus obtained and a read value obtained by pointing the magnified image is subjected to distortion correction or oblique correction so that correction data are obtained. Based on the correction data, a flight speed, a spin rate or a launch angle of the golf ball 1 is calculated.

Abstract: A set of golf clubs including a number of golf clubs which are numbered serially and having progressively increasing loft angles from long irons to short irons. In a cross section of a number of face line grooves arranged on a striking face, the striking face and a groove slope face form a corner portion having a cross-sectional angle which decreases gradually from the long irons to the short irons.

Abstract: The proportion of the torsional rigidity of a base end side grip portion to that of an end side portion fitted with a club head ranges between (1:1) and (4:1). As a result, a golf club shaft arranged so as to have such a proportion of torsional rigidity is increased in the torsional angle of the base end side grip portion thereof as compared with the end side portion thereof which is fitted with the club head thereof.

Abstract: The outer circumferential surface of a mandrel in a bar-shaped configuration is wound with reinforced fiber impregnated with a resin. This reinforced fiber is heat-treated and hardened, to thereby form a reinforced fiber layer in a tubular configuration around the mandrel. The mandrel is provided with a reduced portion in the axial middle thereof, which is decreased in the outside diameter thereof. This mandrel comprises a basic end side member and a terminal end side member which are both connected such that they can be separated at the reduced portion. The separation of both component members of the mandrel is conducted axially in opposite directions, and this allows the detachment of the mandrel out of the reinforced fiber layer.

Abstract: The present invention provides a golf club set comprising differently numbered wood clubs and differently numbered iron clubs. The shaft of each club have reverse deflection which is defined as displacement of a standard shaft point when a predetermined load is applied to the shaft a predetermined distance from the shaft head end with the head end fixed. The reverse deflection of the wood club shafts decreases proportionally as the wood club number increases. The reverse deflection of the iron club shafts decreases progressively as the iron club number increases, and further retains proportionality relative to the proportionally decreasing reverse deflection of the wood club shafts.