To enhance the releasability with a molded golf ball or molding intermediate product and extend the maintenance inspection period by setting the average surface roughness of the inner surface of a cavity to a specified range in a golf ball forming metal mold having upper and lower dies having semispherical recessed cavities.
A metal mold for forming a cover around a core by injection molding as a golf ball forming metal mold is formed of an upper die 1 having a semispherical recessed cavity 11 and a lower die 2 having a semispherical recessed cavity 12, and small projections 3 and so forth for dimple formation are arranged on the inner surface of each cavity 11, 12. The average surface roughness of the inner surface of the cavity and the inner surface of a material passage 13 is set within the range of 5 μm-60 μm. By setting the surface roughness to 5 μm-60 μm, a clearance (air layer) can be formed between the inner surface of the cavities 11 and 12 or the inner surface of the material passage 13 and the ball after molding to facilitate the releasing.
SANO YOSHINORI
OHIRA JUNJI
