Official Answer
Answer
The 'Edge Lead-In' or 'Installation Chamfer' is a tapered section at the end of the shaft that allows the spiral ring to be expanded gradually as it is pushed toward the groove. Without a lead-in, the ring must be expanded abruptly, which often leads to 'over-expansion' and permanent set (loss of 'cling'). A lead-in angle of $15-20$ degrees is recommended. The maximum diameter of the lead-in should be slightly larger than the shaft diameter to ensure the ring clears the shaft shoulder easily. In automated assembly, a smooth, polished lead-in reduces the friction force required to seat the ring, preventing 'buckling' of the ring during the axial push.
