Technical information / Threads and fittings / ISO 7-1
Thread standard
ISO 7-1 · R / Rp / Rc
Taper pipe thread (R / Rp / Rc)
The CSV uses semicolons as separators. The link carries the selected size.
| Size | nthreads/in | Ppitch | dgauge plane | d2 | d1 | agauge length | luseful length, min. | gfitting allowance | Rpdia. tol. | Pipenominal |
|---|---|---|---|---|---|---|---|---|---|---|
| R 1/16 | 28 | 0,907 | 7,723 | 7,142 | 6,561 | 4,0 ±0,9 | 6,5 | 2,5 | ±0,071 | DN3 |
| R 1/8 | 28 | 0,907 | 9,728 | 9,147 | 8,566 | 4,0 ±0,9 | 6,5 | 2,5 | ±0,071 | DN6 |
| R 1/4 | 19 | 1,337 | 13,157 | 12,301 | 11,445 | 6,0 ±1,3 | 9,7 | 3,7 | ±0,104 | DN8 |
| R 3/8 | 19 | 1,337 | 16,662 | 15,806 | 14,950 | 6,4 ±1,3 | 10,1 | 3,7 | ±0,104 | DN10 |
| R 1/2 | 14 | 1,814 | 20,955 | 19,793 | 18,632 | 8,2 ±1,8 | 13,2 | 5,0 | ±0,142 | DN15 |
| R 3/4 | 14 | 1,814 | 26,441 | 25,279 | 24,118 | 9,5 ±1,8 | 14,5 | 5,0 | ±0,142 | DN20 |
| R 1 | 11 | 2,309 | 33,249 | 31,770 | 30,292 | 10,4 ±2,3 | 16,8 | 6,4 | ±0,180 | DN25 |
| R 1 1/4 | 11 | 2,309 | 41,910 | 40,431 | 38,953 | 12,7 ±2,3 | 19,1 | 6,4 | ±0,180 | DN32 |
| R 1 1/2 | 11 | 2,309 | 47,803 | 46,324 | 44,846 | 12,7 ±2,3 | 19,1 | 6,4 | ±0,180 | DN40 |
| R 2 | 11 | 2,309 | 59,614 | 58,135 | 56,657 | 15,9 ±2,3 | 23,4 | 7,5 | ±0,180 | DN50 |
| R 2 1/2 | 11 | 2,309 | 75,184 | 73,705 | 72,227 | 17,5 ±3,5 | 26,7 | 9,2 | ±0,216 | DN65 |
| R 3 | 11 | 2,309 | 87,884 | 86,405 | 84,927 | 20,6 ±3,5 | 29,8 | 9,2 | ±0,216 | DN80 |
| R 4 | 11 | 2,309 | 113,030 | 111,551 | 110,073 | 25,4 ±3,5 | 35,8 | 10,4 | ±0,216 | DN100 |
| R 5 | 11 | 2,309 | 138,430 | 136,951 | 135,473 | 28,6 ±3,5 | 40,1 | 11,5 | ±0,216 | DN125 |
| R 6 | 11 | 2,309 | 163,830 | 162,351 | 160,873 | 28,6 ±3,5 | 40,1 | 11,5 | ±0,216 | DN150 |
Notes
- This table has been compiled by Emsal from the relevant standards. For the full text of the standard, refer to your national standards body.
- The thread seals: the external thread (R) is always tapered (1:16 on diameter); the internal thread can be parallel (Rp) or tapered (Rc). A suitable thread sealant (PTFE tape, liquid sealant) is used.
- Gauge plane: d, d2 and d1 are the diameters at this plane. On the external thread, the gauge plane is one gauge length (a) in from the small end.
- Useful thread length (l): the external thread must have at least this length of full thread; it equals the gauge length plus the fitting allowance (g). The internal thread depth in the valve body is chosen accordingly.
- The thread profile is the same as the G thread (55°, same pitches), but G and R threads do not form a tight joint with each other.
- Accuracy and currency are not guaranteed; use the current edition of the standard for design and purchasing decisions. How the library is compiled →
Dimension letters
| d | Major diameter (at gauge plane) | a | Gauge length |
| d2 | Pitch diameter | l | Useful thread length (min.) |
| d1 | Minor diameter | g | Fitting allowance |
| P | Pitch | T1/2 | Gauge length tolerance |
| n | Threads per inch | T2/2 | Gauge plane position tolerance (internal thread) |
Joint type and P&ID symbol
The R taper male thread screws into an Rp parallel (or Rc taper) female thread. As it is tightened, the taper thread seats on the thread; sealing is made on the thread with tape or compound.
female partmale part, pipegasket / sealing tapethread
- Wrap PTFE tape clockwise on the male thread or apply thread sealant.
- Screw in by hand and tighten with a spanner; the thread does not disappear fully, a few turns may remain visible.
- Do not overtighten: it can crack the female body.
The most common pipe thread for valves, fittings and pipework in Europe and Türkiye. Do not confuse with NPT: the thread angle (55° / 60°) and, in some sizes, the pitch differ.
P&ID: Threaded jointTwo short thin lines perpendicular to the pipeline. Symbol library →
Not to scale; proportions are indicative.
