Stepped Thread Forming Tap for Reverse-Rotation Rubbing

The inside diameter finishing blade is segmented into multiple sections along its length, with each section having a different height. The blade height decreases from the rear end toward the tip end, creating distinct functional zones. The rear sections contact the female thread during forward rotation to perform finishing, while the tip sections are positioned lower to avoid contact during reverse rotation, thus eliminating the rubbing phenomenon.

The inside diameter finishing blade is designed with predetermined height variations before the threading operation. The stepped configuration is pre-established so that during forward rotation, the appropriate blade sections are positioned to finish the inside diameter, and during reverse rotation, the lower tip sections prevent harmful contact. This preliminary structural arrangement proactively prevents the rubbing phenomenon.

The inside diameter finishing blade is divided into multiple height levels along its axial length. The rear sections with greater height are positioned to contact and finish the crest portion of the female thread during forward rotation. The tip sections with reduced height are positioned lower to avoid contact with the female thread during reverse rotation, preventing crest deformation while maintaining effective finishing capability.

Instead of designing a uniform height blade that contacts during both forward and reverse rotations, the invention inverts the approach by creating a non-uniform height profile where the contacting sections are positioned to engage only during forward rotation. The blade geometry is designed so that the effective finishing sections are at the rear, while the forward-facing tip sections are recessed to avoid harmful engagement during reverse motion.