| 摘要 |
A variably threaded screw has a first end and a second end, the first end of the shaft terminating in a tip and the second end having a widened head thereon. A first helical thread portion is located on the shaft adjacent the widened head. A second helical thread portion is located on the shaft adjacent the tip of the shaft. A third helical thread portion is located on the shaft between the first helical thread portion and the second helical thread portion. The first helical thread portion and the second helical thread portion have right hand thread pitches. The third helical thread portion has a left hand thread pitch. A helical ridge having a right hand thread pitch intersects the third helical thread portion. |
