STAINLESS STEEL INTERNAL TOOTH WASHERS ASME B18.21.1

Internal Tooth Washers ASME B18.21.1 — This is the inch-series counterpart to DIN 6797J, built on the same internal-tooth principle - teeth bent inward toward the bore rather than projecting past the washer's outside diameter, so they sit compactly beneath a small fastener head rather than extending past it. That layout suits smaller-headed imperial fasteners specifically, where the head diameter needs to fully cover and engage the teeth for them to bite properly as the joint is tightened; a larger-headed fastener would generally be paired with the external-tooth version instead, where teeth sit at the outer edge and are reached more easily by a bigger head. Functionally, it does the same job as its metric equivalent - biting into both the fastener and the mating surface to resist rotation and self-loosening - but the two are produced to separate imperial and metric standards with their own bore and tooth dimensions, so they are not directly interchangeable even though the working principle is identical. It is specified in general mechanical assembly built to US or imperial fastener standards, wherever vibration resistance is wanted under a small-headed screw without moving to a positive locking method. As with any toothed washer, it provides a useful degree of mechanical resistance to rotation, but for genuinely safety-critical joints, a more positive locking method is generally the safer specification rather than relying on tooth bite alone. Material selection follows the fastener and environment: carbon steel with a protective plating for general indoor assembly, A2 (304-equivalent) stainless for outdoor, washdown, or hygienic equipment, and A4 (316-equivalent) where marine, coastal, or aggressive chemical exposure is a genuine ongoing factor. To specify correctly, match the bore to the imperial fastener diameter and confirm the fastener head is small enough for the internal teeth to be fully covered and engaged once tightened.

FAQs
How does the internal tooth version differ from the external tooth version under the same standard?
The internal tooth washer has teeth positioned near the bore for smaller fastener heads, while the external tooth washer has teeth around the outer edge for larger-headed fasteners such as hex bolts.

How does an ASME B18.21.1 internal tooth washer compare to DIN 6797J?
Both serve the same functional purpose, but they are produced to separate imperial and metric standards with their own bore and tooth dimensions, and are not directly interchangeable.

Is a toothed washer sufficient for a critical anti-loosening application?
It provides a useful degree of mechanical resistance to rotation, but for safety-critical joints, a more positive locking method is generally preferred over a toothed washer alone.