STAINLESS STEEL CURVED WASHERS DIN 137A

• Curved Washers DIN 137A — DIN 137 covers two related spring washer forms - Form A, the curved (single-dish) washer, and Form B, the wave washer - and 137A is essentially a parallel size range to DIN 128A for the same curved concept, with the practical choice between the two standards usually decided by which one a specific drawing or size table references rather than any functional difference. Like any curved washer, it works by flattening under load rather than biting into the joint, generating a light, continuous spring force that takes up thread play or minor tolerance stack-up in an assembly. That makes it a good fit for lightly loaded mechanical assemblies where a small amount of even preload is useful, but a poor substitute for genuine anti-vibration locking, where a split lock washer or toothed washer will outperform it by a wide margin - so it is worth being clear, before specifying, on whether the joint needs tolerance take-up or active loosening resistance, because DIN 137A only really delivers the former. It is also not intended as a load-spreading washer for soft or crushable materials; its light spring action does not provide the bearing area a flat washer offers, so timber or soft-substrate fixings should look to a purpose-built flat or penny washer instead. Material selection tracks the application's environment rather than its load: carbon spring steel suits dry, general mechanical assembly, while A2 (304-equivalent) stainless is the sensible upgrade for anything outdoors or washed down regularly, since a thin spring washer corrodes and loses effective spring action faster than it visibly rusts. A4 (316-equivalent) is only worth specifying where the surrounding assembly already demands it for chloride or chemical exposure. To choose correctly, match the bore to the fastener diameter and confirm from the drawing whether the curved (A) or wave (B) form is actually required.

FAQs
How does the curved form (A) differ from the wave form (B) under DIN 137?
Form A has a single curve across the washer face, while Form B (the wave washer) has multiple waves around its circumference, generally giving a more even spring load distribution around the bolt axis.

Does DIN 137A need to be fitted a particular way up?
No inherent handedness for most applications - it simply needs to seat flat before compressing evenly under tightening.

How do I choose the correct DIN 137A washer?
Match the bore to the fastener diameter and confirm from the drawing whether the curved (A) or wave (B) form is specified.