1. The condition is not proper in the process of heat treament, so that the drilling speed
　　 is not smooth.

　　 SAE T78 1979 Standard

　　 Surface hardness : 550~650 HV CARE HARDNESS
　　 Internal hardness: 320~390 HV CORE HARDNESS
　　　　　　　　　　 　 : 513 HV CORE DEPTH

　　 #4~#6　　　　　　 #7~#12　　　　　 #14
　　 0.05~0.18mm　　　0.1~0.23mm　　　0.13~0.28mm

　2. Because of incorrect die deisgn, the density of screw point is not enough, which will
　　 make the screw brittle.

　3. The thickness of screw's shear is too wide. The standard thickness should be within
　　 following range:

　　 #6: below 0.08mm
　　 #7~#10: below 0.12mm
　　 #12~#14: below 0.14mm

Our solution: We have devoted ourselves to developing and designing drill point die for ten years. We are capable of designing precision die to increase screw point's density. Therefore, our screw is not easy to be brittle when drilling.