Official Answer
Answer
When a wave spring is guided by a rod, the rod diameter $D_{rod}$ must account for the spring's minimum internal diameter $ID_{min}$ throughout its entire stroke. Because wave springs expand radially when compressed, the $ID$ actually increases slightly, but the initial $ID$ at free height is the limiting factor for installation. A clearance of $0.05$mm to $0.5$mm is typically recommended. Furthermore, the surface finish of the pilot rod should be $\text{Ra } 0.8 \mu\text{m}$ or better to minimize friction. If the rod is too small, the spring may 'snaky' or buckle under load, leading to non-linear load delivery and potential contact between the waves and the rod, which causes wear and noise.
