Hose Coupling Screw Threads Machinery's Handbook, 31st Edition
2105
Tolerances for the internal threads are: Minor diameter tolerance = 2 × pitch-diameter tolerance The minimum minor diameter of the internal thread is such as to result in a basic flat, p /8, at the crest when the pitch diameter of the thread is at its minimum value. Major diameter tolerance = pitch-diameter tolerance - 2 h /9 Table 2. Limits of Size and Tolerances for NH External Threads (Nipples) NFPA 1963, 1993 Edition
External Thread (Nipple)
Threads per Inch (tpi)
Minor a Dia.
Major Diameter
Pitch Diameter
Nom. Size
Max. 1.3750 1.3750 1.9900 3.0686 3.6239 4.2439 5.0109 5.7609 6.2600 7.0250
Min.
Toler. 0.0222 0.0222 0.0222 0.0320 0.0360 0.0360 0.0500 0.0500 0.0500 0.0500
Max. 1.2938 1.2938 1.9178 2.9820 3.5156 4.1356 4.8485 5.5985 6.0976 6.8626
Min.
Toler. 0.0111 0.0111 0.0111 0.0160 0.0180 0.0180 0.0250 0.0250 0.0250 0.0250
Max. 1.2126 1.2126 1.8457 2.8954 3.4073 4.0273 4.6861 5.4361 5.9352
8 8 9 6 6 4 4 4 4
1.3528 1.3528 1.9678 3.0366 3.5879 4.2079 4.9609 5.7109 6.2100 6.9750
1.2827 1.2827 1.9067 2.9660 3.4976 4.1176 4.8235 5.5735 6.0726 6.8376
3 ∕ 4
1
1 1 ∕ 2 2 1 ∕ 2
7.5
3
3 1 ∕ 2
4
4 1 ∕ 2
5 6
6.7002 a Dimensions given for the maximum minor diameter of the nipple are figured to the intersection of the worn tool arc with a center line through crest and root. The minimum minor diameter of the nipple shall be that corresponding to a flat at the minor diameter of the minimum nipple equal to p /24 and may be determined by subtracting 11 h /9 (or 0.7939 p ) from the minimum pitch diameter of the nipple. All dimensions are in inches. Table 3. Limits of Size and Tolerances for NH Internal Threads (Couplings) NFPA 1963, 1993 Edition
Internal Thread (Coupling)
Threads per Inch (tpi)
Major a Dia.
Minor Diameter
Pitch Diameter
Nom. Size
Min.
Max. 1.2468 1.2468 1.8799 2.9424 3.4583 4.0833 4.7611 5.5111 6.0102 6.7752
Toler. 0.0222 0.0222 0.0222 0.0320 0.0360 0.0360 0.0500 0.0500 0.0500 0.0500
Min.
Max. 1.3169 1.3169 1.9409 3.0130 3.5486 4.1736 4.8985 5.6485 6.1476 6.9126
Toler. 0.0111 0.0111 0.0111 0.0160 0.0180 0.0180 0.0250 0.0250 0.0250 0.0250
Min.
8 8 9 6 6 4 4 4 4
1.2246 1.2246 1.8577 2.9104 3.4223 4.0473 4.7111 5.4611 5.9602 6.7252
1.3058 1.3058 1.9298 2.9970 3.5306 4.1556 4.8735 5.6235 6.1226 6.8876
1.3870 1.3870 2.0020 3.0836 3.6389 4.2639 5.0359 5.7859 6.2850
3 ∕ 4
1
1 1 ∕ 2 2 1 ∕ 2
7.5
3
3 1 ∕ 2
4
4 1 ∕ 2
5 6
7.0500 a Dimensions for the minimum major diameter of the coupling correspond to the basic flat ( p /8), and the profile at the major diameter produced by a worn tool must not fall below the basic outline. The maximum major diameter of the coupling shall be that corresponding to a flat at the major diameter of the maximum coupling equal to p /24 and may be determined by adding 11 h /9 (or 0.7939 p ) to the maximum pitch diameter of the coupling. All dimensions are in inches. Gages and Gaging: Full information on gage dimensions and the use of gages in check ing the NH thread are given in NFPA Standard No. 1963, 1993 Edition, published by the National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. The information and data taken from this standard are reproduced with the permission of the NFPA.
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