Machinery's Handbook, 31st Edition
996 Taps Table 16. Tap Thread Limits: Metric Sizes, Ground Thread (M Profile Standard Thread Limits in Millimeters) ANSI/ASME B94.9-2008 (R2018) Table 16. (Continued) Tap Thread Limits: Metric Sizes, Ground Thread
Pitch Diameter
Major Diameter
D # Limit
D # Limit
Size mm Pitch
Basic Min.
Max.
Basic
D #
Min.
Max.
D #
Min.
Max.
20 24 30 36 42 48
2.50 20.0 20.20 20.263 18.376 3.00 24.0 24.24 24.34 22.051 3.50 30.0 30.28 30.38 27.727 4.00 36.0 36.32 36.42 33.402 4.50 42.0 42.36 42.46 39.077 5.00 48.0 48.48 48.58 44.103
7 8 9
18.426 18.467 22.114 22.155 27.792 27.844 33.467 33.519 39.155 39.207 44.182 44.246
… … … … … … … … … … … … … … … … … …
10
a Minimum and maximum major diameters are 0.026 larger than shown. b Standard D limit for thread-forming taps. c Minimum and major diameters are 0.039 larger than shown. d Minimum and major diameters are 0.052 larger than shown. e Minimum and major diameters are 0.065 larger than shown.
f These sizes are intended for spark plug applications; use tolerances from Table 2, column D. Notes for Table 16: Inch translations are listed in Table 15. Limits listed in Table 16 are the most commonly used in industry. Not all styles of taps are available with all limits listed. For calculations of limits other than listed, see formulas in Table 4. Table 17. Tap Size Recommendations for Class 6H Metric Screw Threads Nominal Diameter, mm Pitch, mm Recommended Thread Limit Number Internal Threads, Pitch Diameter Min. (mm) Max. (mm) Min. (inch) Max. (inch) 1.6 0.35 D3 1.373 1.458 0.05406 0.05740 2 0.4 D3 1.740 1.830 0.06850 0.07250 2.5 0.45 D3 2.208 2.303 0.08693 0.09067 3 0.5 D3 2.675 2.775 0.10537 0.10925 3.5 0.6 D4 3.110 3.222 0.12244 0.12685 4 0.7 D4 3.545 3.663 0.13957 0.14421 4.5 0.75 D4 4.013 4.131 0.15789 0.16264 5 0.8 D4 4.480 4.605 0.17638 0.18130 6 1 D5 5.350 5.500 0.201063 0.21654 7 1 D5 6.350 6.500 0.2500 0.25591 8 1.25 D5 7.188 7.348 0.28299 0.28929 10 1.5 D6 9.206 9.206 0.35535 0.36244 12 1.75 D6 10.863 11.063 0.42768 0.43555 14 2 D7 12.701 12.913 0.50004 0.50839 16 2 D7 14.701 14.913 0.57878 0.58713 20 2.5 D7 18.376 18.600 0.72346 0.73228 24 3 D8 22.051 22.316 0.86815 0.87858 30 3.5 D9 27.727 28.007 1.09161 1.10264 36 4 D9 33.402 33.702 1.31504 1.32685 The above recommended taps normally produce the class of thread indicated in average materials when used with reasonable care. However, if the tap specified does not give a satisfactory gage fit in the work, a choice of some other limit tap will be necessary. Table 18. Standard Chamfers for Thread Cutting Taps ANSI/ASME B94.9-2008 (R2018)
Chamfer length
Chamfer length
Type of tap
Min.
Max.
Type of tap
Min.
Max.
Bottom
1 P 2 P 3 P 7 P
2 P 3 P 5 P
Semibottom
Taper pipe taps
2 P
Straight threads taps
3 1 ⁄ 2 P
Plug Taper
10 P
P = pitch. The chamfered length is measured at the cutting edge and is the axial length from the point diameter to the theoretical intersection of the major diameter and the chamfer angle. Whenever chamfer length is specified in terms of threads, this length is measured in number of pitches as shown. The point diameter is approximately equal to the basic thread minor diameter.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online