20100119327 | SELF-DRILLING SCREW WITH MULTI-DRILLING PORTIONS - A self-drilling screw with multi-drilling portions mainly comprises a shank, a head and a drilling portion separately disposed on both ends of the shank, and a thread section spiraled on the shank. Wherein, at least one sub-drilling portion formed amid the drilling portion and the thread section further defines a sequence of indentations and prominent areas, and each indentation generates a cutting surface outwardly extended from one side thereof so as to converge the cutting surface with the adjacent prominent area at a cutting ridge. Accordingly, the application of the cutting ridges and the indentations facilitates the drilling portion with the chipping capability and renders an appropriate guidance to redundant debris, thereby efficiently achieving a swift screwing and the lowered screwing resistance to promote the screwing efficiency. | 05-13-2010 |