JIS B 0202 · ISO 228-1
A BSPP parallel thread with a 30 degree female cone seat, usually on a swivel nut. Reads as BSPP on a thread gauge, so the seat is the only thing that tells it apart.
9 sizes55 degree flanksParallel thread30 degree flare cone or seat
A deep, narrow cone - noticeably more pointed than a 37 degree flare. Common on Japanese equipment, usually with a loose female swivel nut.
Where it seals: Metal to metal, a 30 degree female seat against a 30 degree male cone.
Mating two different cone angles is the classic way to make a joint that holds pressure on the bench and weeps in service: the two cones touch on a line instead of a face, and tightening harder cold-flows the softer of the two rather than sealing it.
Sized by BSPP trade size.
Where you will find it: Japanese hydraulic equipment and its export machinery: excavators, forklifts, machine tools.
Also searched as: JIS 30, BSPP 30 degree, Japanese flare, JIS B 0202.
All sizes
| Size | Thread | TPI / pitch | Basic major Ø | Measured across crests | Tube / trade size | Working pressure |
|---|---|---|---|---|---|---|
| -04 JIS 30 (G 1/4) | G 1/4 (19 TPI, 55 degree) | 19 TPI (1.337 mm pitch) | 13.16 mm / 0.518 in | 13.21 mm to 13.5 mm | 1/4 in BSPP trade size | Manufacturer-specific |
| -06 JIS 30 (G 3/8) | G 3/8 (19 TPI, 55 degree) | 19 TPI (1.337 mm pitch) | 16.66 mm / 0.656 in | 16.51 mm to 16.7 mm | 3/8 in BSPP trade size | Manufacturer-specific |
| -08 JIS 30 (G 1/2) | G 1/2 (14 TPI, 55 degree) | 14 TPI (1.814 mm pitch) | 20.95 mm / 0.825 in | 20.5 mm to 20.83 mm | 1/2 in BSPP trade size | Manufacturer-specific |
| -10 JIS 30 (G 5/8) | G 5/8 (14 TPI, 55 degree) | 14 TPI (1.814 mm pitch) | 22.91 mm / 0.902 in | 22.35 mm to 23.1 mm | 5/8 in BSPP trade size | Manufacturer-specific |
| -12 JIS 30 (G 3/4) | G 3/4 (14 TPI, 55 degree) | 14 TPI (1.814 mm pitch) | 26.44 mm / 1.041 in | 26.3 mm to 26.42 mm | 3/4 in BSPP trade size | Manufacturer-specific |
| -16 JIS 30 (G 1) | G 1 (11 TPI, 55 degree) | 11 TPI (2.309 mm pitch) | 33.25 mm / 1.309 in | 33.02 mm to 33.4 mm | 1 in BSPP trade size | Manufacturer-specific |
| -20 JIS 30 (G 1 1/4) | G 1 1/4 (11 TPI, 55 degree) | 11 TPI (2.309 mm pitch) | 41.91 mm / 1.65 in | 41.91 mm to 42.1 mm | 1 1/4 in BSPP trade size | Manufacturer-specific |
| -24 JIS 30 (G 1 1/2) | G 1 1/2 (11 TPI, 55 degree) | 11 TPI (2.309 mm pitch) | 47.8 mm / 1.882 in | 47.6 mm to 47.75 mm | 1 1/2 in BSPP trade size | Manufacturer-specific |
| -32 JIS 30 (G 2) | G 2 (11 TPI, 55 degree) | 11 TPI (2.309 mm pitch) | 59.61 mm / 2.347 in | 59.6 mm to 59.69 mm | 2 in BSPP trade size | Manufacturer-specific |
No working pressure is published for this standard. No two independent sources in the register give the same figure under conditions they both state, and a generic number would be a decoration rather than a rating. Read it from the manufacturer's catalogue.
On paper
Dimensions are as defined by JIS B 0202, ISO 228-1. FittingKey is an independent reference and is not affiliated with, endorsed by or approved by any standards body or fitting manufacturer.
Every value on this page was checked against 3 independent published sources:
| Column | Sources | What they gave |
|---|---|---|
| Dash and trade size | gates-idchart, mcgill-id | Two identification guides, agreeing on the nine sizes published here. One also carries a G 1/8, recorded as a gap. |
| Basic major diameter | iso-228-1, gates-idchart | Both guides state the thread is BSPP, so the basic diameters are ISO 228-1 Table 1 values read directly from the standard. |
| Measured male thread diameter | gates-idchart, mcgill-id | Two identification guides, within 0.8 mm at every size. |