Patent ID: 7938609

Claim:
A method of fastening at least one attachment member to a cast aluminum member with a self-forming screw, which comprises: providing the cast member to which the attachment member is to be fastened with the self-forming screw, the cast member having a prepared hole for receipt of the self-forming screw and the prepared hole not being subjected to prior screw formation; providing the self-forming screw, the self-forming screw including a shaft, a head at one end of the shaft, a tapered self-forming thread portion at an opposite end of the shaft, and a parallel thread portion disposed on the shaft intermediate the head and the tapered self-forming thread portion, wherein the self-forming screw is composed of steel having a strength of 14T which is created by pre-heat treatment rolling, the self-forming thread portion having a 1 to 5 pitch range and a maximum outside diameter or a maximum hypothetical outside diameter of 1 to 10 percent greater than the outer diameter of parallel thread portion, and wherein both the self-forming thread portion and the parallel thread portion are coated with a friction stabilizer; providing the attachment member to be fastened; threading the self-forming screw into the prepared hole of the cast member with the fastening member being positioned for fastening to the cast member, wherein a fitting length of the self-forming screw and the prepared hole is between d and 2.5 d where “d” is the diameter of the self-forming screw; and tightening the self-forming screw into in the prepared hole to form an internal screw thread with a first engagement root portion whereby a percentage of engagement between the internal screw thread and the self-forming screw is between 75 and 90 percent, wherein clearance is not generated on a contact surface between the self-forming screw and the internal screw thread during tightening thereby dispersing and reducing stress on the first engagement root portion of the internal screw thread.