Deformable metallic element

The method of imposing a substantially constant predetermined preload on a pair of opposed members through a substantial range of relative movement of the members toward each other which comprises:

• forming substantially parallel annular surfaces on said members which are in spaced opposed relation, interposing a thin walled tubular element between said surfaces, said element being formed with an odd number of not less than three curved annular convolutions and comprising a hard resilient but ductile metal which work hardens when stressed to beyond the elastic limit, moving said parts relatively in a direction perpendicular to said surfaces to cause said surfaces to engage and axially compress said element in the axial direction, continuing said movement of said parts in said direction through the range of resilient deformation of said element and until said element commences to undergo plastic deformation, and discontinuing said movement of said parts while said element is in said period of plastic deformation and prior to the complete axial collapsing of said element, and fixing said members together against relative movement thereof in a direction to move said surfaces away from each other and with the element confined within an axial space not longer than the length of said element when movement of said parts toward each other is discontinued plus the amount of resilient axial springback of said element.