Machinery's Handbook, 31st Edition
Metric Washers
1739
Metric Washers Metric Plain Washers.— American National Standard ANSI/ASME B18.22M-1981 (R2017) covers general specifications and dimensions for flat, round-hole washers, both soft (as fabricated) and hardened, intended for use in general-purpose applications. Di - mensions are given in the following table. Manufacturers should be consulted for current information on stock sizes. Comparison with ISO Standards.— The washers covered by this ASME Standard are nominally similar to those covered in various ISO documents. Outside diameters were selected, where possible, from ISO/TC2/WG6/N47 “General Plan for Plain Washers for Metric Bolts, Screws, and Nuts.” The thicknesses given in the ASME Standard are simi - lar to the nominal ISO thicknesses, however the tolerances differ. Inside diameters also differ. ISO metric washers are currently covered in ISO 887, “Plain Washers for Metric Bolts, Screws, and Nuts - General Plan.” Types of Metric Plain Washers.— Soft (as fabricated) washers are generally available in nominal sizes 1.6 mm through 36 mm in a variety of materials. They are normally used in low-strength applications to distribute bearing load, to provide a uniform bearing surface, and to prevent marring of the work surface. Hardened steel washers are normally available in sizes 6 mm through 36 mm in the nar row and regular series. They are intended primarily for use in high-strength joints to mini mize embedment, to provide a uniform bearing surface, and to bridge large clearance holes and slots. Metric Plain Washer Materials and Finish.— Soft (as fabricated) washers are made of nonhardened steel unless otherwise specified by the purchaser. Hardened washers are made of through-hardened steel tempered to a hardness of 38 to 45 RC (Rockwell C scale). Unless otherwise specified, washers are furnished with a natural (as fabricated) finish, unplated or uncoated with a light film of oil or rust inhibitor. Metric Plain Washer Designation.— When specifying metric plain washers, the desig nation should include the following data in the sequence shown: description, nominal size, series, material type, and finish, if required. Example: Plain washer, 6 mm, narrow, soft, steel, zinc plated Plain washer, 10 mm, regular, hardened steel.
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