STAINLESS STEEL CURVED SPRING WASHERS DIN 128A

Curved Spring Washers DIN 128A — Not every spring washer works by biting into the joint - DIN 128A takes a gentler approach, formed as a continuous ring pressed into a single dished curve rather than split like DIN 127 or 7980. Under load, that curve simply flattens, generating a light, even spring force that takes up small amounts of thread play or component tolerance rather than gripping the bearing faces. It is best suited to lighter-duty fixings where the goal is compensating for a stack-up of dimensional tolerance, or providing a small amount of continuous preload, rather than actively resisting a joint working loose under vibration. That is the key distinction to get right when specifying: a curved washer is not a strong locking device, and where genuine resistance to loosening is the requirement, a split lock washer (DIN 127/7980) or a toothed washer will do a meaningfully better job. DIN 128A sits close to DIN 137A in function and size range - both cover the curved, single-dish form - and the choice between them in practice usually comes down to which specific standard and size series a drawing calls for rather than any functional difference, so it is worth checking which one is actually specified before substituting. Material selection follows the washer's light-duty role: carbon spring steel is the typical default for general mechanical assembly, while A2 (304-equivalent) stainless is worth specifying the moment the assembly is exposed to moisture or outdoor conditions, since these washers are thin and a corroding one can lose its spring action faster than a heavier component would show equivalent wear. A4 (316-equivalent) is rarely justified on this washer specifically, given its light-duty role, unless the surrounding assembly is already built entirely in A4 for consistency. Choosing correctly means matching the bore to the fastener diameter and confirming this is genuinely a tolerance-take-up application rather than a joint that needs real anti-loosening protection.

FAQs
How does DIN 128A differ from DIN 137A?
DIN 128 and DIN 137 both cover curved and wave washer forms and are closely related; DIN 137A is generally the more current reference for the curved form, so confirm which specific standard the drawing calls for before substituting one for the other.

Can DIN 128A be stacked for more preload?
Not typically recommended; if more spring force or take-up is needed, a heavier curved or wave washer, or a dedicated disc spring to DIN 2093 sized for the load, is a more predictable solution than stacking multiple light washers.

Is a curved spring washer suitable as a locking device?
It provides only light spring take-up rather than a strong locking function; for anti-vibration locking, a split lock washer (DIN 127/7980) or toothed washer is more appropriate.