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
| 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 |
- TPI stands for Threads Per Inch and is a count of the mumber of threads per inch. TPI is used for American fasteners.
- Thread pitch is the distance between the threads and is used for metric fasteners.
- G-threads have a parallel shape in accordance with the DIN-EN-ISO 228-1 standard with flank angle 55o.
- G/R/Rp - Whitworth Pipe Threads (BSPP/BSPT)
- ISO 7-1 Pressure Tight Thread Joints
Example - Typical designation for Thread according ISO 228
- ISO 228 G 3 1/4"
