Official Answer
Answer
Tangential friction occurs in nested wave springs as the turns slide against each other during compression. Upon installation, the lubricant used (e.g., molybdenum disulfide or light machine oil) plays a critical role. If the spring is installed dry, the inter-turn friction can cause the spring to 'bind', resulting in a much higher initial load than calculated by $P = K f$. During the first several cycles (the 'break-in' period), the turns will settle. Engineers should specify a 'pre-set' cycle where the spring is compressed to its work height 3-5 times before final load measurement. This ensures that the tangential friction stabilizes and the spring provides a consistent force in the assembly.
