| 20090074536 | SPIRAL DRIVE FASTENER WITH FRICTION ENGAGEABLE SURFACE - Interference surfaces are constructed on inner transition surfaces between wings of a fastener having a spiral recess. A portion of the transition surface is tapered to provide the interference. A standard driver for a spiral recess will engage the interference surface to create a “stick fit” engagement. The punch is formed using a wire EDM operation to construct tapered surfaces within the die cavity of a hob. The hob is machined down to obtain the desired depth, which is measured up from a gage spot indicative of the sticking point. | 03-19-2009 |
