Official Answer
Answer
For high-volume production, manual installation of spiral rings with pliers or screwdrivers is slow and risks scratching the shaft. A tapered mandrel or 'plug' allows the ring to be gradually expanded as it is pushed axially. This ensures the expansion is uniform around the circumference, preventing localized yielding. The taper angle should be shallow (typically $15^{\circ}$ to $20^{\circ}$) to minimize the force required. Once the ring reaches the groove, it 'snaps' into place. This method is easily automated and ensures the ring's planarity is maintained, which is vital for the performance of the 'clinging' force.
