Spring Washers and Other Lock Washers of Iron or Steel

Helical spring lock washers — the split-ring type that exerts a spring force when compressed — are specifically classified under 7318210030. Other lock washer designs, such as toothed (internal or external serration) lock washers and wave washers, fall under the residual line 7318210090. The distinction matters because some antidumping or trade-remedy scope determinations reference specific washer types by design.

Heading 731821 covers only washers designed to prevent loosening — spring washers and lock washers that function through mechanical tension or tooth engagement. Heading 731822 covers flat, plain washers whose purpose is load distribution rather than locking. An importer must confirm whether a washer has a locking function to determine the correct heading, as the two headings may carry different duty rates and trade-remedy applicability.