DIYUK M4 A2 Stainless Steel Split Lock Spring Washer - DIN 127B - Pack of 50

• Manufactured to DIN 127, Type B (square-end) - the long-standing industry reference for split lock washer sizing, even after the standard's formal withdrawal from the German DIN catalogue.
• Cold-formed from A2 (304-grade) austenitic stainless steel, resisting rust and general atmospheric corrosion far better than plain or zinc-plated carbon steel.
• Works through a dual mechanism: the coiled ring stores spring energy under compression, while the sharp, square-cut ends key slightly into the bearing surfaces - together resisting loosening under vibration.
• Stainless construction means there's no plating to wear through, so the washer can typically be reused across several assembly and disassembly cycles provided it hasn't been fully flattened.

Split lock spring washer manufactured to DIN 127, Type B, cold-formed from A2 (304-grade) austenitic stainless steel into a helical coil with two flat, square-cut ends. It sits under the nut or bolt head of a threaded joint and works mechanically, rather than through friction alone, to resist the loosening effect of vibration and repeated movement. Although DIN 127 was formally withdrawn from the German DIN catalogue in the early 1990s, the Type B (square-end) profile has remained the de facto industry reference for split lock washer dimensions, and continues to be manufactured and stocked worldwide to the same sizing. When the fastener is tightened, the coiled ring is compressed and stores spring energy, which continues pushing back against the bearing face as the joint settles or experiences light-to-moderate vibration. The sharp, square-cut ends also key slightly into the mating surfaces on each side, adding mechanical resistance to counter-rotation on top of the spring action. A2 stainless steel (roughly 17.5-19.5% chromium, 8-10.5% nickel) gives excellent resistance to rust and general corrosion in indoor, outdoor and freshwater conditions. For coastal, marine or other chloride-heavy environments, A2 is prone to pitting over time, and an A4 (316-grade) stainless washer is the more resilient choice for continuous saltwater exposure. When pairing with stainless bolts and nuts, a light anti-seize or lubricant on the threads is worth applying, since stainless-on-stainless fixings can gall (cold-weld) if driven dry. This M4 size suits the corresponding bolt or screw diameter. Typical uses: automotive and freshwater marine-adjacent assembly and repair, where both corrosion and vibration resistance matter; industrial and agricultural machinery subject to continuous vibration; structural steelwork and outdoor construction exposed to weather; electrical enclosures and cabinet hardware needing a non-rusting fixing; and general household maintenance and repair work.