Official Answer
Answer
A tapered mandrel is used to expand the ring gradually as it is pushed onto the shaft. The leading diameter of the mandrel should be slightly larger than the shaft diameter, and the taper angle should be between $3^∘$ and $5^∘$. A steeper angle increases the risk of over-stressing the ring (permanent set), while a shallower angle makes the tool excessively long. The mandrel surface must be hardened (HRC 58-62) and polished to a mirror finish ($R_a < 0.2 μm$) to minimize friction and prevent galling. For multi-turn rings, the mandrel must also account for the 'winding' motion as the ring expands, often requiring a helical lead-in.
