| 摘要 |
This invention relates to drill screws with extending ears to ream a hole in object with the ears breaking off when the screw enters a second object in which a smaller hole is drilled. The inventive screw is adapted to fasten two or more juxtaposed work pieces and it comprises a tip, a shank, and a head, a screw thread on a substantial part of the length of the shank, and means projecting from a part of the shank lying between the tip and the thread. The projecting means is integral with the shank and operative in materials of less than a predetermined hardness to form a hole having a diameter at least as great as the pitch diameter of the thread, but being so weakly connected to the shank that, in materials of more than the predetermined hardness, the projecting means is broken. The projecting means is of non-rectangular configuration and is such that upon being broken there is substantially none of the projecting means remaining which projects beyond the shank. |
