Golf club head with grooves shallower than scorelines and groove pitch and length

Abstract

A golf club head according to this invention is a wood type golf club head including a face portion, a crown portion, and a sole portion. A plurality of grooves are formed in the face portion. The depth of the plurality of grooves is less than 0.025 mm. Each pitch between adjacent grooves of the plurality of grooves ranges from 0.1 mm (inclusive) to 1 mm (inclusive).

What is claimed is: 
     
         1 . A wood type golf club head including a face portion, a crown portion, and a sole portion, wherein
 a plurality of grooves are formed in the face portion,   a depth of the plurality of grooves is less than 0.025 mm,   each pitch between adjacent grooves of the plurality of grooves ranges from 0.1 mm (inclusive) to 1 mm (inclusive), and   grooves on a side of the crown portion in the plurality of grooves have lengths longer than lengths of grooves on a side of the sole portion in the plurality of grooves.   
     
     
         2 . The golf club head according to  claim 1 , wherein an area of a region of the face portion where the plurality of grooves are formed is not less than 50% of an area of the face portion. 
     
     
         3 . The golf club head according to  claim 1 , wherein the plurality of grooves are formed by laser machining. 
     
     
         4 . The golf club head according to  claim 1 , wherein the plurality of grooves are formed at least from a central portion of the face portion to a toe-side portion and a heel-side portion. 
     
     
         5 . The golf club head according to  claim 1 , wherein the plurality of grooves are formed at least in a central portion of the face portion, and
 at least one groove deeper than the plurality of grooves is formed in the central portion.   
     
     
         6 . The golf club head according to  claim 1 , wherein the plurality of grooves are arrayed in an up-and-down direction of the face portion. 
     
     
         7 . The golf club head according to  claim 1 , wherein each groove of the plurality of grooves comprises a straight groove extending in a toe-heel direction, and
 the plurality of grooves are arrayed in an up-and-down direction of the face portion at equal pitches.   
     
     
         8 . The golf club head according to  claim 1 , wherein the depth of the plurality of grooves is not less than 0.003 mm. 
     
     
         9 . The golf club head according to  claim 1 , wherein the width of the plurality of grooves ranges from 0.05 mm (inclusive) to 0.3 mm (inclusive). 
     
     
         10 . The golf club head according to  claim 1 , wherein the lengths of the plurality of grooves are shorter the closer the respective groove is to the sole portion. 
     
     
         11 . The golf club head according to  claim 1 , wherein a formation region of the plurality of grooves in the face portion has a cup shape. 
     
     
         12 . The golf club head according to  claim 1 , wherein a dot-shaped groove is formed in a central portion of the face portion. 
     
     
         13 . The golf club head according to  claim 1 , wherein a shape of a cross section of each groove is an elliptic arc shape, arc shape, triangular shape, rectangular shape, or trapezoidal shape. 
     
     
         14 . The golf club head according to  claim 1 , wherein the plurality of grooves are formed in a central portion of the face portion which is an impact area, in a toe-side portion of the face portion and in a heel-side portion of the face portion, and
 the impact area is a band-shaped portion passing through a center of the face portion and having a width of 1.68 inches.