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ISO 228 - Pipe Threads where Pressure Tight Joints are not made on the Threads

Requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes.

The ISO 228 "Pipe Threads where Pressure-tight Joints are not made on the Threads" consists of the following parts:

  • ISO 228-1:2000 Dimensions, tolerances and designation
  • ISO 228-2:1987 Verification by means of limit gauges
ISO 228 - Pipe Threads where Pressure Tight Joints are not made on the Threads
G Size
(in)
Major (Outside) Diameter (mm)
Minor (Nut) Diameter
(mm)
Core Hole Diameter
(mm)
Thread Count
(TPI)
Thread Pitch
(mm)
G 1/8 9.73 8.85 8.80 28 0.907
G 1/4 13.16 11.89 11.80 19 1.337
G 3/8 16.66 15.39 15.25 19 1.337
G 1/2 20.95 19.17 19.00 14 1.814
G 5/8 22.91 21.13 21.00 14 1.814
G 3/4 26.44 24.66 24.50 14 1.814
G 7/8 30.20 28.42 28.25 14 1.814
G 1 33.25 30.93 30.75 11 2.309
G 1 1/8 37.90 35.58 35.30 11 2.309
G 1 1/4 41.91 39.59 39.25 11 2.309
G 1 3/8 44.32 42.00 41.70 11 2.309
G 1 1/2 47.80 45.48 45.25 11 2.309
G 1 3/4 53.74 51.43 51.10 11 2.309
G 2 59.61 57.29 57.00 11 2.309
G 2 1/4 65.71 63.39 63.10 11 2.309
G 2 1/2 75.18 72.86 72.60 11 2.309
G 2 3/4 81.53 79.21 78.90 11 2.309
G 3 87.88 85.56 85.30 11 2.309
G 3 1/4 93.98 91.66 91.50 11 2.309
G 3 1/2 100.33 98.01 97.70 11 2.309
G 3 3/4 106.68 104.30 104.00 11 2.309
G 4 113.03 110.71 110.40 11 2.309

Example - Typical designation for Thread according ISO 228

  • ISO 228 G 3 1/4"
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6.20.11

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