Special Features:

Internally threaded center hole - .500-20 unf-2b, interpreted by fed-std-h28 and asme y14.6, accepted or rejected by system 21 of fed-std-h28/20.

Properties:

A circular-shaped item designed to maintain predetermined distance between assembled parts and/or for distributing pressure or preventing endwise movement between member parts. It has a solid cross-section and two flat parallel bearing surfaces. The distance between the bearing surfaces perpendicular to the axis of the centrally located hole shall not exceed 25 percent of the outside diameter. The diameter of the centrally located hole must exceed 75 percent of the outside diameter. Excludes laminated items. For items manufactured from impregnated graphite or lubricated nonmetallic materials, excluding felt or plastics, see gasket. For items manufactured from lubricated plastics, see bearing, washer, thrust. For items manufactured from lubricated felt, see felt, mechanical, preformed. Excludes disk, valve; insulator washer; and shim. See also spacer, plate and spacer, sleeve.