Golf club head and method for manufacturing same

1. A golf club head having a hollow therein and a head volume of not less than 100 cc and less than 350 cc, and comprising a head main body and a substantially cup-shaped face member which are united with each other, wherein

the face member integrally includes a face portion having a club face for hitting a ball, and a turnback extending backwardly of the head from a peripheral edge of the club face,

an inner surface on the hollow side, of the face member is provided with a groove extending along the boundary of the turnback with the face portion,

the face member is a press-formed part whose turnback is bent by press working,

said groove is a sole-side groove extending along only a sole-side part of the boundary, and

the sole-side groove extends in the toe-heel direction of the head by at least 5 mm toward the toe and toward the heel of the head from a position in the toe-heel direction corresponding to that of a sweet spot of the club face.

2. The golf club head according to claim 1 , wherein

the face portion is provided with

a first section formed in a central part of the face portion and having a constant thickness,

a second section formed outside the first section and having a constant thickness smaller than that of the first section, and

a transitional section extending annularly around the first section and having a variable thickness decreasing gradually from the first section towards the second section,

on the crown-side of the first section, the transitional section extends to said boundary so that the intersection therebetween is positioned on the heel side of the sweet spot,

on the sole-side of the first section, the transitional section extends to said boundary so that the intersection therebetween is positioned on the toe side of the sweet spot,

the part of the face portion on the toe side of the transitional section and the part of the face portion on the heel side of the transitional section constitute said second section, and

said sole-side groove has a toe-side end positioned within the extent of said intersection on the sole-side of the first section.

3. The golf club head according to claim 2 , wherein

the sole-side groove extends in the toe-heel direction of the head by at least 5 mm toward the toe and toward the heel of the head from the sweet spot of the club face, and

the distance in the toe-heel direction between the sweet spot and the heel-side end of the club face is larger than the distance in the toe-heel direction between the sweet spot and the toe-side end of the club face.

4. The golf club head according to claim 1 , wherein

the sole-side groove extends in the toe-heel direction of the head by at least 5 mm toward the toe and toward the heel of the head from the sweet spot of the club face, and

the sole-side groove has a heel-side end and a toe-side end such that the distance in the toe-heel direction between the sweet spot and the heel-side end of the sole-side groove is larger than the distance in the toe-heel direction between the sweet spot and the toe-side end of the sole-side groove.

5. A golf club head having a hollow therein and a head volume of not less than 100 cc and less than 350 cc, and comprising a head main body and a substantially cup-shaped face member which are united with each other, wherein

the face member integrally includes a face portion having a club face for hitting a ball, and a turnback extending backwardly of the head from a peripheral edge of the club face,

an inner surface on the hollow side, of the face member is provided with a groove extending along the boundary of the turnback with the face portion,

the face member is a press-formed part whose turnback is bent by press working, and

the thickness of the face member measured at the groove is 0.5 to 2.0 mm.