7318.21.00 - Spring washers and other lock washers

This category encompasses spring washers and other types of lock washers specifically manufactured from iron or steel. These articles are designed to be used in conjunction with screws, bolts, and nuts to prevent loosening due to vibration or stress. Spring washers, in particular, are characterized by their ability to exert a spring force against the assembled components, thereby maintaining tension and securing the connection. This classification is distinct from other non-threaded articles within the 7318.20 series, such as plain washers, rivets, or cotters and cotter pins, which serve different functional purposes within mechanical assemblies.

The distinction from sibling categories is crucial for accurate classification. While "Other washers" (7318.22.00.00) covers flat washers and other washer types not specifically designed for locking, this category is reserved for washers with inherent spring action or designs intended for a locking function. Rivets (7318.23.00.00) are permanent fasteners, and cotters and cotter pins (7318.24.00.00) are used to secure pins or shafts.

The subcategories provided further refine the classification of spring washers and lock washers. "Helical spring lock washers" (7318.21.00.30) specifically refers to those washers formed into a helical shape to provide a spring effect. "Other" (7318.21.00.90) would encompass any remaining types of spring or lock washers not meeting the specific criteria of helical spring lock washers but still fulfilling the general locking function.