Synthetic plate fixing screw - has conically narrowing head with two pitch threaded cylindrical shaft and four sided pyramidal point

摘要

The screw has a smooth head and wood screw thread for fixture of eternite plates on a batten frame, the screw being made of stainless steel, and its head (2) having a back cut on its circumference (4). The screw head (2) narrows conically in the direction of the shaft (1), and has a cross slot (7). The shaft (1) is cylindrical, and has a two pitch thread, the pitches (8,9) having different peak diameters. The shaft (1) has a drilling or cutting point (10) which is in the form of a sharp edged, four sided pyramid.