Thread identification
Metric Parallel Port Threads (ISO 6149 / DIN 3852)
European and Asian components often use straight metric port threads sealing with an O-ring (ISO 6149) or a sealing washer (DIN 3852) at the shoulder — the metric equivalent of SAE ORB, and just as intolerant of taper-thread substitutes.
Identify it
Four checks at the bench.
- 01
Straight metric thread with a machined shoulder or O-ring groove above it
- 02
Measure pitch: 1.5 mm is most common (M10×1 through M48×2 exist)
- 03
Look for the ISO 6149 port identification groove on newer components
- 04
Confirm seal style: captive O-ring, ED elastomer ring, or bonded washer
Don't confuse it with…
- BSPP ports measure deceptively close at several sizes — Whitworth pitch vs metric pitch settles it
- Tapered metric (rare, but real) and NPT substitutions both wreck parallel ports
Reference
Size chart.
| Size | Thread |
|---|---|
| M10×1 | small pilots/gauges |
| M12×1.5 | common |
| M14×1.5 | common |
| M18×1.5 | common |
| M22×1.5 | common |
| M27×2 | larger ports |
A1 stocks it.
Unsure even after the checks? Bring the fitting to the counter — gauging an unknown thread takes us about a minute. (817) 589-7101.
Metric Parallel Port Threads (ISO 6149 / DIN 3852) — FAQs
What does the groove on my port fitting mean?
A machined identification groove on the hex marks an ISO 6149 metric port fitting — O-ring sealed, straight metric thread.
My import valve port strips NPT fittings — what is it?
It's almost certainly a straight metric or BSPP port; forcing taper threads into it damages the casting. Measure and use the correct port adapter.