1、AMERICAN PIPE THREADS 1847 American National Standard pipe threads described in the following paragraphs provide taper and straight pipe threads for use in various combinations and with certain modifica- tions to meet these specific needs. American National Standard Taper Pipe Threads.The basic dime
2、nsions of the ANSI Standard taper pipe thread are given in Table 4. Form of Thread: The angle between the sides of the thread is 60 degrees when measured in an axial plane, and the line bisecting this angle is perpendicular to the axis. The depth of the truncated thread is based on factors entering
3、into the manufacture of cutting tools and the making of tight joints and is given by the formulas in Table 4 or the data in Table 1 obtained from these formulas. Although the standard shows flat surfaces at the crest and root of the thread, some rounding may occur in commercial practice, and it is i
4、ntended that the pipe threads of product shall be acceptable when crest and root of the tools or chasers lie within the limits shown in Table 1. Table 1. Limits on Crest and Root of American National Standard External and Internal Taper Pipe Threads, NPT ANSI/ASME B1.20.1-1983 (R1992) All dimensions
5、 are in inches and are given to four or five decimal places only to avoid errors in computations, not to indicate required precision. Pitch Diameter Formulas: In the following formulas, which apply to the ANSI Standard taper pipe thread, E 0= pitch diameter at end of pipe; E 1= pitch diameter at the
6、 large end of the internal thread and at the gaging notch; D = outside diameter of pipe; L 1= length of hand-tight or normal engagement between external and internal threads; L 2= basic length of effective external taper thread; and p = pitch = 1 number of threads per inch. Thread Length: The formul
7、a for L 2determines the length of the effective thread and includes approximately two usable threads that are slightly imperfect at the crest. The nor- INTERNAL THREAD EXTERNAL THREAD Threads per Inch Height of Sharp V Thread, H Height of Pipe Thread, h Truncation, f Width of Flat, F, Equivalent toT
8、runcation Max. Min. Min. Max. Min. Max. 27 0.03208 0.02963 0.02496 0.0012 0.0036 0.0014 0.0041 18 0.04811 0.04444 0.03833 0.0018 0.0049 0.0021 0.0057 14 0.06186 0.05714 0.05071 0.0024 0.0056 0.0027 0.0064 11 1 2 0.07531 0.06957 0.06261 0.0029 0.0063 0.0033 0.0073 8 0.10825 0.10000 0.09275 0.0041 0.0
9、078 0.0048 0.0090 Max.h H Crest Root Root Crest Crest MaximumTruncation MinimumTruncation MinimumTruncation MaximumTruncation MaximumTruncation MaximumTruncation MinimumTruncation MinimumTruncation E 0 D 0.05D 1.1 + () p = E 1 E 0 0.0625L 1 + =1848 AMERICAN PIPE THREADS mal length of engagement, L 1
10、 , between external and internal taper threads, when assem- bled by hand, is controlled by the use of the gages. Taper: The taper of the thread is 1 in 16, or 0.75 inch per foot, measured on the diameter and along the axis. The corresponding half-angle of taper or angle with the center line is 1 deg
11、ree, 47 minutes. Tolerances on Thread Elements.The maximum allowable variation in the commer- cial product (manufacturing tolerance) is one turn large or small from the basic dimen- sions. The permissible variations in thread elements on steel products and all pipe made of steel, wrought iron, or br
12、ass, exclusive of butt-weld pipe, are given in Table 2. This table is a guide for establishing the limits of the thread elements of taps, dies, and thread chasers. These limits may be required on product threads. On pipe fittings and valves (not steel) for steam pressures 300 pounds and below, it is
13、 intended that plug and ring gage practice as set up in the Standard ANSI B1.20.1 will pro- vide for a satisfactory check of accumulated variations of taper, lead, and angle in such product. Therefore, no tolerances on thread elements have been established for this class. For service conditions wher
14、e a more exact check is required, procedures have been developed by industry to supplement the regulation plug and ring method of gaging. Table 2. Tolerances on Taper, Lead, and Angle of Pipe Threads of Steel Products and All Pipe of Steel, Wrought Iron, or Brass ANSI B1.20-1983 (R1992) (Exclusive o
15、f Butt-Weld Pipe) For tolerances on height of thread, see Table 1. The limits specified in this table are intended to serve as a guide for establishing limits of the thread elements of taps, dies, and thread chasers. These limits may be required on product threads. Table 3. Internal Threads in Pipe
16、Couplings, NPSC for Pressuretight Joints with Lubricant or Sealer ANSI/ASME B1.20.1-1983 (R1992) Nominal Pipe Size Threads per Inch Taper on Pitch Line ( 3 4in./ft) Lead in Length of Effective Threads 60 Degree Angle of Threads, Degrees Max. Min. 1 16 , 1 8 27 + 1 8 1 16 0.003 2 1 2 1 4 , 3 8 18 + 1
17、 8 1 16 0.003 2 1 2 , 3 4 14 + 1 8 1 16 0.003 a a The tolerance on lead shall be 0.003 in. per inch on any size threaded to an effective thread length greater than 1 in. 2 1, 1 1 4 , 1 1 2 , 2 11 1 2 + 1 8 1 16 0.003 a 1 1 2 2 1 2and larger 8 + 1 8 1 16 0.003 a 1 1 2 Nom.Pipe- Size Thds.per Inch Min
18、or aDia. a As the ANSI Standard Pipe Thread form is maintained, the major and minor diameters of the inter- nal thread vary with the pitch diameter. All dimensions are given in inches. Pitch Diameter b b The actual pitch diameter of the straight tapped hole will be slightly smaller than the value gi
19、ven when gaged with a taper plug gage as called for in ANSI/ASME B1.20.1. Nom. Pipe Thds. per Inch Minor aDia. Pitch Diameter b Min. Min. Max. Min. Min. Max. 1 8 27 0.340 0.3701 0.3771 1 1 2 11 1 2 1.745 1.8142 1.8305 1 4 18 0.442 0.4864 0.4968 2 11 1 2 2.219 2.2881 2.3044 3 8 18 0.577 0.6218 0.6322
20、 2 1 2 8 2.650 2.7504 2.7739 1 2 14 0.715 0.7717 0.7851 3 8 3.277 3.3768 3.4002 3 4 14 0.925 0.9822 0.9956 3 1 2 8 3.777 3.8771 3.9005 1 11 1 2 1.161 1.2305 1.2468 4 8 4.275 4.3754 4.3988 1 1 4 11 1 2 1.506 1.5752 1.5915 L 2 0.80D 6.8 + () p =AMERICAN PIPE THREADS 1849 Table 4. Basic Dimensions, Ame
21、rican National Standard Taper Pipe Threads, NPT ANSI/ASME B1.20.1-1983 (R1992) For all dimensions, see corresponding reference letter in table. Angle between sides of thread is 60 degrees. Taper of thread, on diameter, is 3 4inch per foot. Angle of taper with center line is 147. The basic maximum th
22、read height, h, of the truncated thread is 0.8 pitch of thread. The crest and root are truncated a minimum of 0.033 pitch for all pitches. For maximum depth of truncation, see Ta b l e 1. Nominal Pipe Size Outside Dia. of Pipe, D Threads per Inch, n Pitch of Thread, p Pitch Diameter at Beginning of
23、External Thread, E 0 Handtight Engagement Dia., a E 1 a Also pitch diameter at gaging notch (handtight plane). Effective Thread, Dia., E 2 Length, bL 1 b Also length of thin ring gage and length from gaging notch to small end of plug gage. Length, c L 2 c Also length of plug gage. In. In. 1 16 0.312
24、5 27 0.03704 0.27118 0.160 0.28118 0.2611 0.28750 1 8 0.405 27 0.03704 0.36351 0.1615 0.37360 0.2639 0.38000 1 4 0.540 18 0.05556 0.47739 0.2278 0.49163 0.4018 0.50250 3 8 0.675 18 0.05556 0.61201 0.240 0.62701 0.4078 0.63750 1 2 0.840 14 0.07143 0.75843 0.320 0.77843 0.5337 0.79179 3 4 1.050 14 0.0
25、7143 0.96768 0.339 0.98887 0.5457 1.00179 11 . 3 1 5 11 1 2 0.08696 1.21363 0.400 1.23863 0.6828 1.25630 1 1 4 1.660 11 1 2 0.08696 1.55713 0.420 1.58338 0.7068 1.60130 1 1 2 1.900 11 1 2 0.08696 1.79609 0.420 1.82234 0.7235 1.84130 22 . 3 7 5 11 1 2 0.08696 2.26902 0.436 2.29627 0.7565 2.31630 2 1
26、2 2.875 8 0.12500 2.71953 0.682 2.76216 1.1375 2.79062 3 3.500 8 0.12500 3.34062 0.766 3.38850 1.2000 3.41562 3 1 2 4.000 8 0.12500 3.83750 0.821 3.88881 1.2500 3.91562 4 4.500 8 0.12500 4.33438 0.844 4.38712 1.3000 4.41562 5 5.563 8 0.12500 5.39073 0.937 5.44929 1.4063 5.47862 6 6.625 8 0.12500 6.4
27、4609 0.958 6.50597 1.5125 6.54062 8 8.625 8 0.12500 8.43359 1.063 8.50003 1.7125 8.54062 10 10.750 8 0.12500 10.54531 1.210 10.62094 1.9250 10.66562 12 12.750 8 0.12500 12.53281 1.360 12.61781 2.1250 12.66562 14 OD 14.000 8 0.12500 13.77500 1.562 13.87262 2.2500 13.91562 16 OD 16.000 8 0.12500 15.76
28、250 1.812 15.87575 2.4500 15.91562 18 OD 18.000 8 0.12500 17.75000 2.000 17.87500 2.6500 17.91562 20 OD 20.000 8 0.12500 19.73750 2.125 19.87031 2.8500 19.91562 24 OD 24.000 8 0.12500 23.71250 2.375 23.86094 3.2500 23.91562 L 4 V Imperfect Threads due to Chamfer on die Taper of Thread 1 in 16 Measur
29、ed on Diameter L 3 L 1 L 5 E 3 L 2 2p E 0 E 1 E 5 E 2 D1850 AMERICAN PIPE THREADS All dimensions given in inches. Increase in diameter per thread is equal to 0.0625/n. The basic dimensions of the ANSI Standard Taper Pipe Thread are given in inches to four or five decimal places. While this implies a
30、 greater degree of precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are so expressed for the purpose of eliminating errors in computations. Engagement Between External and Internal Taper Threads.The normal length of engagement between external and internal
31、 taper threads when screwed together handtight is shown as L 1in Table 4. This length is controlled by the construction and use of the pipe thread gages. It is recognized that in special applications, such as flanges for high-pressure work, longer thread engagement is used, in which case the pitch d
32、iameter E 1(Table 4) is maintained and the pitch diameter E 0at the end of the pipe is proportionately smaller. Railing Joint Taper Pipe Threads, NPTR.Railing joints require a rigid mechanical thread joint with external and internal taper threads. The external thread is basically the same as the ANS
33、I Standard Taper Pipe Thread, except that sizes 1 2through 2 inches are shortened by 3 threads and sizes 2 1 2through 4 inches are shortened by 4 threads to permit the use of the larger end of the pipe thread. A recess in the fitting covers the last scratch or imperfect threads on the pipe. Table 5.
34、 Basic Dimensions, American National Standard Taper Pipe Threads, NPT ANSI/ASME B1.20.1-1983 (R1992) Nominal Pipe Size Wrench Makeup Length for Internal Thread Va n i s h Thread, (3.47 thds.), V Overall Length External Thread, L 4 Nominal Perfect External Threads a Height of Thread, h Basic Minor Di
35、a. at Small End of Pipe, b K 0 Length, c L 3 Dia., E 3 Length, L 5 Dia., E 5 1 16 0.1111 0.26424 0.1285 0.3896 0.1870 0.28287 0.02963 0.2416 1 8 0.1111 0.35656 0.1285 0.3924 0.1898 0.37537 0.02963 0.3339 1 4 0.1667 0.46697 0.1928 0.5946 0.2907 0.49556 0.04444 0.4329 3 8 0.1667 0.60160 0.1928 0.6006
36、0.2967 0.63056 0.04444 0.5676 1 2 0.2143 0.74504 0.2478 0.7815 0.3909 0.78286 0.05714 0.7013 3 4 0.2143 0.95429 0.2478 0.7935 0.4029 0.99286 0.05714 0.9105 1 0.2609 1.19733 0.3017 0.9845 0.5089 1.24543 0.06957 1.1441 1 1 4 0.2609 1.54083 0.3017 1.0085 0.5329 1.59043 0.06957 1.4876 1 1 2 0.2609 1.779
37、78 0.3017 1.0252 0.5496 1.83043 0.06957 1.7265 2 0.2609 2.25272 0.3017 1.0582 0.5826 2.30543 0.06957 2.1995 2 1 2 0.2500 d 2.70391 0.4337 1.5712 0.8875 2.77500 0.100000 2.6195 3 0.2500 d 3.32500 0.4337 1.6337 0.9500 3.40000 0.100000 3.2406 3 1 2 0.2500 3.82188 0.4337 1.6837 1.0000 3.90000 0.100000 3
38、.7375 4 0.2500 4.31875 0.4337 1.7337 1.0500 4.40000 0.100000 4.2344 5 0.2500 5.37511 0.4337 1.8400 1.1563 5.46300 0.100000 5.2907 6 0.2500 6.43047 0.4337 1.9462 1.2625 6.52500 0.100000 6.3461 8 0.2500 8.41797 0.4337 2.1462 1.4625 8.52500 0.100000 8.3336 10 0.2500 10.52969 0.4337 2.3587 1.6750 10.650
39、00 0.100000 10.4453 12 0.2500 12.51719 0.4337 2.5587 1.8750 12.65000 0.100000 12.4328 14 OD 0.2500 13.75938 0.4337 2.6837 2.0000 13.90000 0.100000 13.6750 16 OD 0.2500 15.74688 0.4337 2.8837 2.2000 15.90000 0.100000 15.6625 18 OD 0.2500 17.73438 0.4337 3.0837 2.4000 17.90000 0.100000 17.6500 20 OD 0
40、.2500 19.72188 0.4337 3.2837 2.6000 19.90000 0.100000 19.6375 24 OD 0.2500 23.69688 0.4337 3.6837 3.0000 23.90000 0.100000 23.6125 a The length L 5from the end of the pipe determines the plane beyond which the thread form is imper- fect at the crest. The next two threads are perfect at the root. At
41、this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe. L 5= L 2 2p. b Given as information for use in selecting tap drills. c Three threads for 2-inch size and smaller; two threads for larger sizes. d Military Specification MILP7105 g
42、ives the wrench makeup as three threads for 3 in. and smaller. The E 3dimensions are then as follows: Size 2 1 2in., 2.69609 and size 3 in., 3.31719. AMERICAN PIPE THREADS 1851 Straight Pipe Threads in Pipe Couplings, NPSC.Threads in pipe couplings made in accordance with the ANSI B1.20.1 specificat
43、ions are straight (parallel) threads of the same thread form as the ANSI Standard Taper Pipe Thread. They are used to form pressuretight joints when assembled with an ANSI Standard external taper pipe thread and made up with lubricant or sealant. These joints are recommended for comparatively low pr
44、essures only. Straight Pipe Threads for Mechanical Joints, NPSM, NPSL, and NPSH.While external and internal taper pipe threads are recommended for pipe joints in practically every service, there are mechanical joints where straight pipe threads are used to advan- tage. Three types covered by ANSI B1
45、.20.1 are: Free-Fitting Mechanical Joints for Fixtures (External and Internal), NPSM: Standard iron, steel, and brass pipe are often used for special applications where there are no internal pressures. Where straight thread joints are required for mechanical assemblies, straight pipe threads are oft
46、en found more suitable or convenient. Dimensions of these threads are given in Table 6. Table 6. American National Standard Straight Pipe Threads for Mechanical Joints, NPSM and NPSL ANSI/ASME B1.20.1-1983 (R1992) Nominal Pipe Size Threads per Inch External Thread Internal Thread Allowance Major Dia
47、meter Pitch Diameter Minor Diameter Pitch Diameter Max. a Min. Max. Min. Min. a Max. Min. b Max. Free-fitting Mechanical Joints for FixturesNPSM 1 8 27 0.0011 0.397 0.390 0.3725 0.3689 0.358 0.364 0.3736 0.3783 1 4 18 0.0013 0.526 0.517 0.4903 0.4859 0.468 0.481 0.4916 0.4974 3 8 18 0.0014 0.662 0.6
48、53 0.6256 0.6211 0.603 0.612 0.6270 0.6329 1 2 14 0.0015 0.823 0.813 0.7769 0.7718 0.747 0.759 0.7784 0.7851 3 4 14 0.0016 1.034 1.024 0.9873 0.9820 0.958 0.970 0.9889 0.9958 1 11 1 2 0.0017 1.293 1.281 1.2369 1.2311 1.201 1.211 1.2386 1.2462 1 1 4 11 1 2 0.0018 1.638 1.626 1.5816 1.5756 1.546 1.555
49、 1.5834 1.5912 1 1 2 11 1 2 0.0018 1.877 1.865 1.8205 1.8144 1.785 1.794 1.8223 1.8302 2 11 1 2 0.0019 2.351 2.339 2.2944 2.2882 2.259 2.268 2.2963 2.3044 2 1 2 8 0.0022 2.841 2.826 2.7600 2.7526 2.708 2.727 2.7622 2.7720 3 8 0.0023 3.467 3.452 3.3862 3.3786 3.334 3.353 3.3885 3.3984 3 1 2 8 0.0023 3.968 3.953 3.8865 3.8788 3.835 3.848 3.8888 3.8988 4 8 0.0023 4.466 4.451 4.384
