Patent attributes
A fastener includes a shank, a head connected thereto, a drilling portion opposite to the head and a plurality of first threads and second threads spirally disposed on the shank. The second threads are affixed to the first threads and provided with a plurality of opening slots defined thereon. The opening slots expose portions of the first threads therethrough. The first threads divide the shank into a plurality of shank segments, each of which has a base part and a transition part extending outward from the base part to be inclined by 5 to 10 degrees. The opening slots formed on the second threads provide an auxiliary cutting effect and accommodate cut debris. The first threads reinforce the bearing and drilling force of the second threads. The inclined transition part helps increase the ability of resisting the driving torsion and attain an anti-loosening force, thereby increasing the fastening effect.
