description is given below of an embodiment with reference to the drawings . fig1 is a perspective view of a head blank 1 when viewed from the back side and sole side thereof . fig2 is a front view of the head blank 1 when viewed from the sole side . the head blank 1 is a metal - made blank manufactured by casting or by forging . the head blank 1 includes a face part 2 , a sole part 3 constituting its bottom surface , a hosel part 4 for mounting a shaft thereon and a back surface 5 . on the back surface 5 side of the sole part 3 , there are formed grooves 10 constituted of recesses as a measure of the machining amount . in this embodiment , the groove 10 includes a first groove and a second groove . the first groove extends along a first direction crossing obliquely a ball flying direction and a direction defined by a line connecting the toe side with the heel side . the second groove extends along a second direction crossing obliquely the first direction so that the groove 10 provides a mesh - like appearance . the recess such as the groove 10 may be formed by a providing a projection on a mold for manufacturing the head blank 1 , or may be formed by machining , for example , by pressing or by cutting . the width of the groove 10 may preferably be 0 . 1 mm or more , and may more preferably be 0 . 2 mm or more . the width of the groove 10 may preferably be 1 mm or less , and may more preferably be 0 . 8 mm or less . the excessively large groove width can raise a fear of giving a bad influence on the impact resilience property or the like of the sole part . the excessively small groove width can raise a fear of collapsing the groove in polishing or in grinding , or disturbing visual confirmation of the groove . the depth of the groove 10 may preferably be 0 . 1 mm or more , and may more preferably be 0 . 2 mm or more . the depth of the groove 10 may preferably be 1 mm or less , and may more preferably be 0 . 6 mm or less . the excessively large groove depth may be excessively larger than necessary with respect to the polishing amount or grinding amount , or can raise a fear of giving a bad influence on the impact resilience property or the like of the sole part . the excessively small groove depth can raise a fear of eliminating the groove before a necessary amount of polishing or grinding is performed . the section shape of the groove 10 may be square as shown in fig3 , or may be a u - like shape ( not shown ). also , like a groove 11 shown in fig4 , it may be a trapezoidal section shape the groove width of which becomes smaller toward the deep ( groove bottom surface ) side . or , like a groove 12 shown in fig5 , it may be a composite section shape in which the entrance side is a large width portion 12 a , the deep side is a small width portion 12 b , and the boundary between them is a step surface 12 c . that is , the section shape of the large width portion 12 a is a first trapezoidal section shape the width of which becomes smaller toward the deep ( groove bottom surface ) side , whereas the section shape of the small width portion 12 b is a second trapezoidal section shape the width of which becomes smaller toward the deep ( groove bottom surface ) side and is smaller than that of the first trapezoidal section shape . the first and second trapezoidal section shapes are connected together and the bottom surface of the first trapezoidal section shape provides a step surface 12 c . in polishing or grinding the back surface 5 side of the sole part of the head blank 1 having the grooves 10 , when the depth of the groove 10 is reduced down to a specified depth , polishing or grinding may preferably be ended . since the specified depth is corresponding to an expected shape , the polishing or grinding amount provides a specified amount , thereby enabling the sole shape to provide the expected shape with high precision . in the case of a groove 11 shown in fig4 , when the groove width of the groove 11 is reduced down to a specified width , polishing or grinding may preferably be ended . to measure the groove width is often easier than to measure the groove depth . however , in the case of the groove 11 as well , when the depth of the groove 11 is reduced down to a specified depth , polishing or grinding may be ended . besides , the specified width is corresponding to the expected shape . in the case of a groove 12 shown in fig5 , when the outer surface of the head blank 1 being polished or ground becomes flush with the stepped surface 12 c , polishing or grinding may preferably be ended . when machining reaches the stepped surface 12 c , since the groove width is reduced and the groove is no longer a two - step - shaped groove , an operator can confirm the machining amount simply by viewing the appearance of the head blank 1 . however , in this case as well , when polishing or grinding advances to the second trapezoidal section shape 12 b and thus the groove width becomes small , polishing or grinding may be ended . in the invention , as shown in fig6 , there are previously formed a first groove 13 having a comparatively small depth and a second groove 14 having a depth larger than the depth of the first groove , and when the first groove 13 disappears but the second groove 14 remains , polishing or grinding may be ended . since the groove 13 disappears and the groove 14 remains , the operator can confirm the machining amount simply by viewing the appearance of the blank . in all cases shown in fig4 to 6 , the polishing or grinding amount can be secured as accurately as specified and thus a golf club head the sole shape of which becomes an expected shape with high precision can be manufactured . by allowing the groove to remain after polishing or grinding , in a checking operation to be executed later , an operator can confirm at a glance that that it is not machined excessively . fig7 a and 7b show an example for machining ( polishing or grinding ) a head blank 1 having , on the back surface 5 side of the sole part 3 , grooves 10 serving as a measure for maintaining the shape of the sole part 3 . fig7 a is a front view of the sole part 3 before machined , and fig7 b is a front view of the sole part 3 when machined excessively . a broken line in fig7 b shows the rear edge of the sole part before machined . in this example , as shown in fig7 b , it can be seen at a glance that the half of the groove 10 is eliminated by machining and the sole shape is not maintained . in this manner , the groove 10 can also be used as a measure for maintaining the sole shape before machined . in the above embodiment , the grooves 10 have a meshed shape . however , it may also be a parallel - lines shape , a zigzag shape , or an undulated shape . also , the grooves may have any one of various shapes , for example , a circular shape , an oval shape , a square shape , a u - like shape , an l - like shape , a cruciform . in the above embodiment , as the recesses , there are formed the grooves 10 . however , recessed holes may also be formed , or grooves and recessed holes may be both formed . also , in the above embodiment , the grooves are formed on the back surface side of the sole part 3 . however , the recesses may also be formed in other portions . the invention can be applied not only to the iron type golf head but also to golf heads having other shapes .
a method for manufacturing golf club head includes : preparing a head blank for an iron type golf club head , the head blank having a recess serving as a measure of polishing or grinding at least in a portion of a sole part of the head blank ; and polishing or grinding the head blank according to the recess .