Therefore, in order to sustain impact upon hammering, it is effective that the screw is formed so that the outer diameter of the smaller diameter parallel thread part 15 is equal to or smaller than 1.8 mm for the C type steel plate structural material having {HEAD ~ the thickness} of 0.5 mm or {TAIL ~ 0.8 mm} 
Therefore , in order to sustain impact upon hammering , it is effective that the screw is formed so that the outer diameter of the smaller diameter parallel thread part 15 is equal to or smaller than 1.8 mm for the C type steel plate structural material having { HEAD ~ the thickness } of 0.5 mm or { TAIL ~ 0.8 mm }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL