| 摘要 |
A metallic fastener or insert of the type adapted to thread itself into a recess formed in a plastic work piece has a multiplicity of uniformly angularly spaced, longitudinally extending flutes, each of which is formed with a flat bottom surface and with flat side walls angularly related to define between them an included angle of about 60 DEG . The flutes are each formed to a depth greater than the root diameter of the external threads of the insert, that is, the flat bottom surface of each flute lies in a plane tangential to an imaginary circle of a diameter smaller than the root diameter of the external thread of the insert. |
