Machinery's Handbook, 31st Edition
688 Preferred Metric Sizes Preferred Metric Sizes.— American National Standard ANSI B32.4M-1980 (R1994), presents series of preferred metric sizes for round, square, rectangular, and hexagonal metal products. Table 1 gives preferred metric diameters from 1 to 320 millimeters for round metal products. Wherever possible, sizes should be selected from the Preferred Series shown in the table. A Second Preference Series is also shown. A Third Preference Series not shown in the table is: 1.3, 2.1, 2.4, 2.6, 3.2, 3.8, 4.2, 4.8, 7.5, 8.5, 9.5, 36, 85, and 95. This standard has now been consolidated into ANSI/ASME B32.100-2016, see Metric Sizes for Flat Metal Products on page 2708. ANSI/ASME B4.2-1978 (R2009) states that the basic size of mating parts should be chosen from the first choice sizes listed in Table 1. Most of the Preferred Series sizes are derived from the American National Standard “10 series” of preferred numbers (see American National Standard for Preferred Numbers on page 687). Most of the Second Preference Series are derived from the “20 series” of preferred numbers. Third Preference sizes are generally from the “40 series” of preferred numbers. For preferred metric diameters less than 1 millimeter, preferred across flat metric sizes of square and hexagon metal products, preferred across flat metric sizes of rectangular metal products, and preferred metric lengths of metal products, reference should be made to the Standard. Table 1. American National Standard Preferred Metric Sizes ANSI/ASME B4.2-1978 (R2009) Basic Size, mm Basic Size, mm Basic Size, mm Basic Size, mm 1st Choice 2nd Choice 1st Choice 2nd Choice 1st Choice 2nd Choice 1st Choice 2nd Choice 1 … 6 … 40 … 250 … … 1.1 … 7 … 45 … 280 1.2 … 8 … 50 … 300 … … 1.4 … 9 … 55 … 350 1.6 … 10 … 60 … 400 … … 1.8 … 11 … 70 … 450 2 … 12 … 80 … 500 … … 2.2 … 14 … 90 … 550 2.5 … 16 … 100 … 600 … … 2.8 … 18 … 110 … 700 3 … 20 … 120 … 800 … … 3.5 … 22 … 140 … 900 4 … 25 … 160 … 1000 … … 4.5 … 28 … 180 … … 5 … 30 … 200 … … … … 5.5 … 35 … 220 … … Preferred Metric Sizes for Metal Products.— See Metric Sizes for Flat Metal Products on page 2708.
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