The reasons caused heading products of surface defect:
1. Bias for the reason of 2nd blow setting and machine adjustment improperly.
2. Crooked head for the reason of 1st blow setting and machine adjustment improperly.
3. Screw head profile is not round because of 1st blow choice improper and 1st blow forming process is not full.
4. Heading Die cracked fir the reason of heading die breakage or the radius of heading die design improper to cause it collided & scraped with 2nd blow.
5. Screw head with two layers because of 1st blow forming procession improperly.
6. Burrs caused by the reason of 1st blow forming procession improperly. The mainly reason of 1st punch pin and punch die's distance too big but the 1st punch pin too short to make the burrs.
7.Craked angle for the reason of 2nd punches broken or 2nd punches collided with heading die.
8.Craked on head because of the raw material of wire or the 1st blow design mistake or the usage of lube problem.