Screw specification definition and understanding一. Thread typeA: triangular thread (60 degrees) : combining/lockB: work triangular thread (55 degrees) : combine/lockC: trapezoidal thread (30 or 29 degrees) : power transmissionD: square thread (90 degrees) : power transmission二. Common screw types:A: the Machine Screw, Machine ScrewB: Tapping Screw, self-tapping Screw (points used in metal and used...