{HEAD ~ The manufacturing method} 1, wherein the sandblasting is performed up to a distance that is smaller than a depth of {TAIL ~ the groove} 
{ HEAD ~ The manufacturing method } 1 , wherein the sandblasting is performed up to a distance that is smaller than a depth of { TAIL ~ the groove }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL