Metric self-tapping locking screw and the manufacturing method thereof

Abstract

A metric self-tapping locking screw comprises a screw head which is connected to a thread locking body by a screw rod. The thread locking body and the self-tapping tip are provided with a screw thread on the surface. The self-tapping tip is arranged at the root of the thread locking body; the screw thread adopts the basic structure of the standard ordinary triangular thread. The flank angle back to the fastened surface is 15-20° and the flank angle of the screw thread facing the fastened surface is 30°. The metric self-tapping locking screw in the Invention make the installed parts to be fastened have higher axial clamping force and static loosing moment, which solves the attenuation problem of axial clamping force and static moment of fastened parts.

What is claimed is: 
     
       1. A metric self-tapping locking screw, comprising a screw head, a screw rod, a thread locking body, a self-tapping tip and a screw thread; the screw head is connected to the thread locking body with the screw rod; the thread locking body and the self-tapping tip are provided with the screw thread on the surface; the self-tapping tip is arranged at the root of the thread locking body; the screw thread adopts the basic structure of the standard ordinary triangular thread; a flank angle of the screw thread back to the fastened surface is 15-20° and another flank angle of the screw thread facing the fastened surface is 30°; a crest of the screw thread is in a plane transition structure or a natural circular arc transition structure;
 wherein the screw thread is divided into eight equal parts by eight mean lines; the eight mean lines include one-eighth line, two-eighth line, three-eighth line, four-eighth line, five-eighth line, six-eighth line, seven-eighth line and eight-eighth line; the intersection of the four-eighth line and the crest is a first crossing point; the intersection of the two-eighth line and the flank side back to the fastened surface is a second crossing point; a tangency arc between the first crossing point and the second crossing point is a rounded root of thread; 
 wherein the two-eighth line and the screw thread intersect at a third tangency point; the three-eighth line and the screw thread intersect at a fourth crossing point; line connected the third tangency point and the fourth crossing point forms a thread root-diameter angle with the two-eighth line; the thread root-diameter angle is 20°. 
 
     
     
       2. The metric self-tapping locking screw according to  claim 1 , wherein the rounded root of thread constitutes the asymmetry root-diameter structure of the metric self-tapping locking screw together with the thread root-diameter angle. 
     
     
       3. The metric self-tapping locking screw according to  claim 1 , wherein the cross-section of the self-tapping tip is in a triangular circular arc transition structure and forms an angle of 8-15° with the plane of the thread locking body; the crests of the self-tapping tip transit to the thread locking body from small to large in a cone way and the screw threads on the thread locking body gradually diminish to the self-tapping tip in compliance with the crest shape; the length of the screw thread on the self-tapping tip is equal to or less than the nominal diameter of the screw thread on the thread locking body.