(a) This standard covers general and dimensional data pertinent to the various types of screw and captive washer assemblies, otherwise known as SEMS. The word SEMS is recognized in the United States as a generic term applicable to screw and washer assemblies.

Also included in this standard are appendixes to illustrate the relative proportions of plain and conical washer SEMS and provide documentation on the washer dimensions for SEMS with screw types and head styles that have been relegated to “not recommended for new design” status.

(b) This standard does not duplicate the general and dimensional data pertaining to components of SEMS as found in the following standards.

ASME B18.2.1, Square and Hex Bolts and Screws (Inch Series).
ASME B18.3, Socket Cap, Shoulder, and Set Screws.
ASME B18.6.3, Machine Screws, Tapping Screws and Metallic Drive Screws (Inch Series).
ASME B18.21.1, Lock Washers.
ASME B18.22.1, Plain Washers.
SAE J773, Conical Spring Washers.

NOTE: The word lock, which appears in the names of products in this standard, is a generic term historically associated with their identification and is not intended to imply an indefinite permanency of fixity in attachments where the fasteners are used.