Machinery's Handbook, 31st Edition
976 Taps Standard System of Ground Thread Tap Limits and Identification for Metric Screw Threads, M Profile.— All calculations for metric taps use millimeter values. When US customary values are needed, they are translated from the three-place millimeter tap diameters only after the calculations are completed. Table 4. Tap Thread Limits and Tolerances ANSI/ASME B94.9-2008 (R2018) Formulas for Metric Thread (Ground Thread) Min. major diameter Basic diameter W Max. pitch diameter Basic diameter Y Max. major diameter Min. maj. dia. X Min. pitch diameter Max. pitch dia. Z = + = + = + = + W Constant to add with basic major diameter (W 0.08P) X Major diameter tolerance Y Amount over basic for maximum pitch diameter Z Pitchdiameter tolerance = = = = = 0.30 0.024 0.025 0.039 0.039 0.052 0.052 0.015 0.015 0.020 0.020 0.35 0.028 0.025 0.039 0.039 0.052 0.052 0.015 0.015 0.020 0.020 0.40 0.032 0.025 0.039 0.052 0.052 0.052 0.015 0.015 0.020 0.025 0.45 0.036 0.025 0.039 0.052 0.052 0.052 0.015 0.020 0.020 0.025 0.50 0.040 0.025 0.039 0.052 0.052 0.065 0.015 0.020 0.025 0.025 0.60 0.048 0.025 0.052 0.052 0.065 0.065 0.020 0.020 0.025 0.025 0.70 0.056 0.041 0.052 0.052 0.065 0.065 0.020 0.020 0.025 0.025 0.75 0.060 0.041 0.052 0.065 0.065 0.078 0.020 0.025 0.025 0.031 0.80 0.064 0.041 0.052 0.065 0.065 0.078 0.020 0.025 0.025 0.031 0.90 0.072 0.041 0.052 0.065 0.065 0.078 0.020 0.025 0.025 0.031 1.00 0.080 0.041 0.065 0.065 0.078 0.091 0.025 0.025 0.031 0.031 1.25 0.100 0.064 0.065 0.065 0.078 0.091 0.025 0.031 0.031 0.041 1.50 0.120 0.064 0.065 0.078 0.078 0.091 0.025 0.031 0.031 0.041 1.75 0.140 0.064 … 0.078 0.091 0.104 … 0.031 0.041 0.041 2.00 0.160 0.064 … 0.091 0.091 0.104 … 0.041 0.041 0.041 2.50 0.200 0.063 … 0.091 0.104 0.117 … 0.041 0.041 0.052 3.00 0.240 0.100 … 0.104 0.104 0.130 … 0.041 0.052 0.052 3.50 0.280 0.100 … 0.104 0.117 0.130 … 0.041 0.052 0.052 4.00 0.320 0.100 … 0.104 0.117 0.143 … 0.052 0.052 0.064 4.50 0.360 0.100 … … 0.130 0.143 … 0.052 0.052 0.064 5.00 0.400 0.100 … … 0.130 0.156 … … 0.064 0.064 5.50 0.440 0.100 … … 0.143 0.156 … … 0.064 0.064 6.00 0.480 0.100 … … 0.143 0.156 … … 0.064 0.064 Dimensions are given in millimeters. The tables and formulas are used in determining the limits and tolerances for ground thread metric taps having a thread lead angle not in excess of 5 ° , unless otherwise specified. They apply only to metric thread having a 60 ° form with a P /8 flat at the major diameter of the basic thread form. All calculations for metric taps are done using millimeter values as shown. When inch values are needed, they are translated from the three-place millimeter tap diameters only after calculations are performed. The tap major diameter must be determined from a specified tap pitch diameter: the mini mum major diameter equals the maximum specified tap pitch diameter minus constant Y , plus 0.64951905 P plus constant W . Minimum major diameter Max. tap pitch diameter Y 0.64951904 P W = − + + For intermediate pitches, use value of next coarser pitch. Lead Tolerance: ± 0.013 mm within any two threads not farther apart than 25 mm. Angle Tolerance: ± 30 ′ in half angle for 0.25 to 2.5 pitch; ± 25 ′ in half angle for 2.5 to 4 pitch; and ± 20 ′ in half angle for 4 to 6 pitch. D or DU Limits: When the maximum tap pitch diameter is over basic pitch diameter by an even multiple of 0.013 mm (0.000512 in. reference), or the minimum tap pitch diameter limit is under basic pitch diameter by an even multiple of 0.013 mm, the taps are marked P Pitch (mm) W (0.08 P ) X Y Z M1.6 to M6.3 Over M6.3 to to M25 Over M25 to M90 Over M90 M1.6 to M6.3 Over M6.3 to to M25 Over M25 to M90 Over M90
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