Machinery's Handbook, 31st Edition
2014 Metric Screw Threads M Profile The root profile of the internal thread must not be smaller than the basic profile. The maximum major diameter must not be sharp. General Symbols.— The general symbols used to describe the metric screw thread forms are shown in Table 1. Table 1. American National Standard Symbols for Metric Threads ANSI/ASME B1.13M-2005 (R2015) Symbol Explanation D Major Diameter Internal Thread D 1 Minor Diameter Internal Thread D 2 Pitch Diameter Internal Thread d Major Diameter External Thread d 1 Minor Diameter External Thread d 2 Pitch Diameter External Thread d 3 Rounded Form Minor Diameter External Thread P Pitch r External Thread Root Radius T Tolerance T D 1 , T D 2 Tolerances for D 1 , D 2 T d , T d 2 Tolerances for d , d 2 ES Upper Deviation, Internal Thread [Equals the Allowance (Fundamental Deviation) Plus the Tolerance]. See Fig. 5. EI Lower Deviation, Internal Thread Allowance (Fundamental Deviation). See Fig. 5. G , H Letter Designations for Tolerance Positions for Lower Deviation, Internal Thread g , h Letter Designations for Tolerance Positions for Upper Deviation, External Thread es Upper Deviation, External Thread Allowance (Fundamental Deviation). See Fig. 5. In the ISO system es is always negative for an allowance fit or zero for no allowance. ei Lower Deviation, External Thread [Equals the Allowance (Fundamental Deviation) Plus the Tolerance]. See Fig. 5. In the ISO system ei is always negative for an allowance fit. H Height of Fundamental Triangle LE Length of Engagement LH Left Hand Thread Standard M Profile Screw Thread Series.— The standard metric screw thread series for general purpose equipment’s threaded components design and mechanical fasteners is a coarse thread series. Their diameter/pitch combinations are shown in Table 4. These diameter/pitch combinations are the preferred sizes and should be the first choice as appli cable. Additional fine pitch diameter/pitch combinations are shown in Table 5. Table 2. American National Standard General Purpose and Mechanical Fastener Coarse Pitch Metric Thread—M Profile Series ANSI/ASME B1.13M-2005 (R2015) Nom.Size Pitch Nom.Size Pitch Nom.Size Pitch Nom.Size Pitch 1.6 0.35 6 1 22 2.5 a 56 5.5 2 0.4 8 1.25 24 3 64 6 2.5 0.45 10 1.5 27 3 a 72 6 b 3 0.5 12 1.75 30 3.5 80 6 b 3.5 0.6 14 2 36 4 90 6 b 4 0.7 16 2 42 4.5 100 6 b 5 0.8 20 2.5 48 5 … … a For high strength structural steel fasteners only. b Designated as part of 6 mm fine pitch series in ISO 261. All dimensions are in millimeters.
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