STAINLESS STEEL EXTERNAL TOOTH WASHERS ASME B18.21.1

External Tooth Washers ASME B18.21.1 — The external-tooth version under ASME B18.21.1 is the inch-series equivalent of DIN 6797A - teeth splayed outward past the washer's outside diameter, suited to larger-headed imperial fasteners such as hex bolts, where the head diameter is generous enough to bear fully on teeth positioned at the outer edge. As the joint tightens, those teeth bite into both the fastener face and the mating surface, giving mechanical resistance to rotation in the same way as the internal-tooth version, just positioned to suit fasteners with bigger heads. Beyond the anti-loosening function, the exposed outer teeth increase contact area against the joint face, which is often the deciding factor where electrical bonding or earthing continuity across an imperial-fastened joint matters, in addition to the mechanical locking benefit. It works on the same principle as DIN 6797A, but the two follow separate imperial and metric standards with their own dimensions, so they should not be treated as directly interchangeable even where the function is identical. It is a common specification in general mechanical assembly built to US or imperial fastener standards, wherever hex bolts or similarly large-headed fasteners need vibration resistance without the added complexity of a tab washer or the single-use nature of a nylon insert nut. Material selection should reflect both mechanical duty and, where relevant, electrical bonding requirements: carbon steel with a plating for general indoor assembly, A2 (304-equivalent) stainless for outdoor, washdown, or general corrosive environments, and A4 (316-equivalent) for marine, coastal, or chemically exposed installations, where reliable long-term electrical continuity and mechanical grip both depend on resisting pitting corrosion. To specify correctly, match the bore to the imperial fastener diameter and confirm the fastener head or nut is genuinely large enough to bear fully on the external teeth.

FAQs
How does the external tooth version differ from the internal tooth version?
The external tooth washer has teeth on the outer edge for larger-headed fasteners, while the internal tooth washer has teeth near the bore, intended for smaller-headed fasteners.

How does an ASME B18.21.1 external tooth washer compare to DIN 6797A?
Both work on the same biting principle, but they follow separate imperial and metric standards with their own dimensions, and should not be treated as directly interchangeable.

What materials are these washers commonly supplied in?
Typically carbon steel with a zinc or other protective plating, and stainless steel grades for corrosion-resistant imperial fastener assemblies.