Fastener

Abstract

A fastener includes a shank defining a shank root, a head, a drilling portion and main threads. The main threads divide the shank root into recessed root sections. Each main thread with two cutting faces which converge at an edge is inclined to a shank axis by 60 to 82 degrees. At least one main lobe projects from the recessed root section and flares outward to at least a midpoint of at least one cutting face between the recessed root section and the edge of the main thread. The inclination allows the main threads to have a large rotating angle for increasing cutting and drilling efficiency. The extension of the main lobe supports the main thread to bear the drilling stress to prevent the shank and main threads from snapping and allow debris accommodation to provide a firm fastening effect.

Dependencies are inferred from the claim text.