Official Answer
Answer
'Shingling' refers to a failure mode in multi-turn springs where the turns shift radially and overlap or 'nest' incorrectly during compression. This is primarily caused by excessive radial clearance between the spring and the bore or shaft. When the spring is compressed, the helix angle changes, and if not constrained, the turns will follow the path of least resistance. The result is a sudden jump in the spring rate and localized plastic deformation. The solution involves tightening the diametrical clearances or utilizing a 'shim end' design, which provides a flat 360-degree contact surface that helps maintain the axial alignment of the turns during the entire stroke.
