ORB Weld Fittings Guide
ORB (SAE O-ring boss) ports seal with an O-ring in a chamfer at the top of a straight thread. This guide covers dash sizes, threads and O-rings, and lists our ORB female weld fittings with hole cuts.
Part of the Weld Fittings Product Guide.
How Each Thread Seals
ORB (SAE O-Ring Boss)
An ORB port (SAE J1926) is a straight UNF / UN female thread with a precise chamfer at the top. The male ORB fitting carries an O-ring. When it is tightened, the O-ring is squeezed into the chamfer and seals there.
- Seal: the O-ring in the port chamfer. The threads only hold the fitting in.
- No thread sealant.
- Same threads as AN by dash size, different seal. An ORB port has a chamfer and no cone. Use an ORB male fitting, with its O-ring, in an ORB port.
- ORB O-rings are the AS568 900-series. The last two digits match the dash size (see the O-ring column below).
How We Check the Threads
Our ORB ports are checked with 2B GO / NO-GO thread plug gauges per ASME B1.2. The GO plug must thread in by hand the full thread length; the NO-GO plug may start but must not enter more than 3 complete turns.
Our ORB Female Weld Fittings
CNC machined from 6061-T6 aluminum, 1018 steel or 304 stainless bar. SAE J1926 port profile, 2B threads. A pilot step helps locate the fitting in a tank hole cut larger than the pilot OD. Hole cut: between the pilot OD and the OD. Shop: Aluminum | Steel | Stainless
| SAE size | Thread | O-ring (AS568) | OD | Height | Pilot OD | Pilot height | Hole cut | Aluminum | Steel | Stainless |
|---|---|---|---|---|---|---|---|---|---|---|
| -3 | 3/8-24 2B | 903 | 0.928" | 0.472" | 0.803" | 0.142" | 0.803–0.928" | 21092 | 22030 | 23030 |
| -4 | 7/16-20 2B | 904 | 1.007" | 0.551" | 0.882" | 0.165" | 0.882–1.007" | 21093 | 22031 | 23031 |
| -5 | 1/2-20 2B | 905 | 1.086" | 0.551" | 0.961" | 0.165" | 0.961–1.086" | 21094 | 22032 | 23032 |
| -6 | 9/16-18 2B | 906 | 1.164" | 0.610" | 1.039" | 0.183" | 1.039–1.164" | 21095 | 22033 | 23033 |
| -8 | 3/4-16 2B | 908 | 1.361" | 0.689" | 1.236" | 0.192" | 1.236–1.361" | 21096 | 22034 | 23034 |
| -10 | 7/8-14 2B | 910 | 1.519" | 0.787" | 1.394" | 0.236" | 1.394–1.519" | 21097 | 22035 | 23035 |
| -12 | 1-1/16-12 2B | 912 | 1.794" | 0.906" | 1.670" | 0.272" | 1.670–1.794" | 21098 | 22036 | 23036 |
| -14 | 1-3/16-12 2B | 914 | 1.952" | 0.906" | 1.827" | 0.272" | 1.827–1.952" | 21099 | 22037 | 23037 |
| -16 | 1-5/16-12 2B | 916 | 2.109" | 0.906" | 1.984" | 0.272" | 1.984–2.109" | 21100 | 22038 | 23038 |
| -20 | 1-5/8-12 2B | 920 | 2.463" | 0.906" | 2.338" | 0.272" | 2.338–2.463" | 21106 | 22039 | 23039 |
| -24 | 1-7/8-12 2B | 924 | 2.739" | 0.906" | 2.614" | 0.272" | 2.614–2.739" | 21102 | 22040 | 23040 |
| -32 | 2-1/2-12 2B | 932 | 3.650" | 0.906" | 3.520" | 0.272" | 3.520–3.650" | 21105 | 22041 | 23041 |
Port threads per SAE J1926-1. O-rings per AS568 900-series.
FAQ
Which O-ring do I need?
An AS568 900-series O-ring. The last two digits match the dash size: -8 uses a 908. See the O-ring column.
What size hole do I cut in the tank?
Cut the hole between the pilot OD and the OD. See the Hole cut column.
References: SAE J1926-1 (straight thread O-ring port); AS568 (900-series boss O-rings); ASME B1.2 (gages for Unified threads). Dash, thread and O-ring sizes were cross-checked against Parker and O-Ring Handbook charts.