Self-tapping screw for fastening a metal corrugated board

摘要

A self-tapping screw consists of a head and a threaded shank which is provided with a blade, a first threaded portion contiguous to the blade, and a second threaded portion contiguous to the head and greater in length, tooth pitch and tooth depth than the first threaded portion. The self-tapping screw is fastened onto a corrugated board such that the blade and the first threaded portion are securely embedded in a girder, and that the second threaded portion is securely embedded in an insulation layer located between the corrugated board and the girder.