The official name of plum screw is iso10664 screw or internal plum screw, also known as star screw. It is a kind of screw fastener developed and listed in 1967 by Conrad Textron company. Because Kangjia applied for a patent with the trade name of "torox", it was also called as "the screw". Plum screw is widely used in automobile, motorcycle, bicycle brake system, hard disk, computer system and consumer electronic products.
Design principle of plum screw:
According to the design, the protrusion deviation of the plum head screw is better than that of the Phillips head screw or the straight head screw. Phillips head screws are designed to deflect the driver bulge to prevent over tightening, while the plum head screws are designed to prevent the screw driver bulge from deflecting. This design shift comes from the widespread use of automatic torque control screwdrivers used in factories. Torque control screwdrivers can be designed to provide a predetermined torque stably, rather than relying on tools to slide out the screw head after reaching a certain torque, risking the risk of damaging the screw driver tip, screw head, or even the workpiece.
The plum head is designed to apply a higher torque than a normal hex head of similar size without damaging the screw head and / or tools. The interaction between male and female components of general hexagon and plum screw heads. The gap between components is exaggerated for clarity.
Features of plum screw:
The contact angle of the quincunx design is closer to 90 degrees than that of the hexagon head, so the potential destructive radial force will be much smaller under the same torque. This feature allows the screw head to be made smaller at the same torque, with the advantage of less space. However, the disadvantage of the older head is that the smaller the internal "Star" is, the more likely it is to corrode and cause the plum blossom driver to slide and damage the head, making it more difficult to remove than the traditional hexagon bolt.
Structural form of plum blossom screw:
There is a kind of screw called safety plum blossom screw, which can prevent the insertion of standard plum blossom driver (or straight line driver) by the convex point in the center of the screw head.
The other version is called the external plum blossom screw. The head of the screw is in the shape of a plum blossom screwdriver, and it is turned with a plum blossom socket. The standard size "e" of the external plum blossom is incompatible with the "t" size of the standard plum blossom of (for example, an E40 sleeve is too large for the head of T40, while the E8 plum blossom sleeve can fit with the T40 plum blossom).