PIPE COUPLINGS (STATE STANDARD 8955-75)
LOCK NUTS (STATE STANDARD 8961-75 )
Pipe 20 State Standard 3262-75.
Table 4.12
| Nominal bore, Dy, mm | Thread G, inch | External diameter, mm | Internal diameter, mm | Thickness of a wall pipe, s, mm | L1, mm | L2, mm | L, mm | ||
| Thin-walled | Normal | Thick-walled | |||||||
| 3/8 | 16.663 | 14.951 | 2.2 | 2.8 | 8.5 | ||||
| 1/2 | 20.956 | 18.532 | 2.5 | 2.8 | 3.2 | ||||
| 3/4 | 26.442 | 24.119 | 2.5 | 2.8 | 3.2 | 10.5 | |||
| 33.250 | 30.292 | 2.8 | 3.2 | 11.0 | |||||
| 41.912 | 38.954 | 2.8 | 3.2 | 13.0 | |||||
| 47.805 | 44.847 | 3.5 | 15.0 | ||||||
| 59.616 | 56.659 | 3.5 | 4.5 | 17.0 |
The example of the conventional denotation of a steel non-galvanized pipe with the nominal bore 20 mm:
Pipe fittings are used for joining pipe different lengths and to provide changes of direction, branch connection at different angles or to effect a change in size. The fittings are made for screwed, flanged or welded connection.
A drawings and structural sizes of the pipe fittings is pointed below.

Figure 4.27 – Conventional drawings of lock nut
Table 4.13
| Nominal bore, Dy, mm | Thread G, inch | External diameter, mm | Internal diameter, mm | H, mm | D, mm | S, mm | Chamfer с, mm |
| 3/8 | 16.663 | 14.951 | 31,2 | ||||
| 1/2 | 20.956 | 18.532 | 36,9 | 1,5 | |||
| 3/4 | 26.442 | 24.119 | 41,6 | 1,5 | |||
| 33.25 | 30.292 | 53,1 | |||||
| 41.912 | 38.954 | 63,5 | |||||
| 47.805 | 44.847 | 69,3 | |||||
| 59.616 | 56.659 | 86,5 |
The example of the conventional denotation of a lock-nut with the nominal bore 20 mm: Lock-nut 20 State Standard 8961-75.

Figure 4.28 – Conventional drawings of pipe coupling
Table 4.14
| Nominal bore, Dy, mm | Thread G, inch | L, mm | l , mm | D1, mm | D2, mm | B, mm | b1, mm | b2, mm | h, mm | Number of ribs | Chamfer с, mm |
| 3/8 | 3.5 | ||||||||||
| 1/2 | 1,5 | ||||||||||
| 3/4 | 10.5 | 32.5 | 2.5 | 2.5 | 1,5 | ||||||
| 39.5 | 2.5 | 2.5 | 4.5 | 2.5 | |||||||
| 2.5 | |||||||||||
| 68.5 | 3.5 | 3.5 |
Note. Sizes of external and internal diameters are resulted in table 4.12.
The example of the conventional denotation of a pipe coupling with the nominal bore 20 mm: Pipe Coupling 20 State Standard 8955-75.