A self-tapping and/or self-carving stud having two or more right angle elongate grooves of alternate length in the tapered thread or projecting helical ribs. The right angled grooves enable tapping debris to accumulate in the grooves to help lock the threads for fastening the stud, particularly in irregular...http://www.google.es/patents/US4673323?utm_source=gb-gplus-sharePatente US4673323 - Self tapping stud
