Official Answer
Answer
Buckling in Crest-to-Crest springs occurs when the free height to mean diameter ratio ($L_0/D$) exceeds approximately $1.5$. When compressed, the spring acts like a long column and deflects laterally rather than axially. This lateral instability causes the spring to rub against the shaft or bore, leading to friction-induced hysteresis and potential failure. To solve buckling, designers either increase the diameter, decrease the free height by using a material with a higher spring rate, or provide a guide (either a shaft or a bore) with a clearance of approximately $5-10\%$ of the radial wall.
