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SAE J1453 · ISO 8434-3 · ASME B1.1
ORFS Fitting Size Chart
Dash sizes -4 to -24 for ORFS (O-ring face seal, SAE J1453 / ISO 8434-3) connections: tube OD, UN/UNF thread, typical reading range and face O-ring numbers.
Quick answer
On ORFS connections, the seal is made by an O-ring sitting in a groove on the flat face of the male part; the thread only holds the joint. The threads differ from the JIC thread of the same dash size: -4 = 9/16-18 UNF (14.29 mm), -6 = 11/16-16 UN (17.46 mm), -8 = 13/16-16 UN (20.64 mm), -12 = 1-3/16-12 UN (30.16 mm), -16 = 1-7/16-12 UN (36.51 mm). The dash number gives the tube OD in sixteenths of an inch.
SAE J1453 · ISO 8434-3 · ASME B1.1
Size chart
ORFS (O-ring face seal) fitting dimensions, SAE J1453 / ISO 8434-3
| Dash size | Tube / pipe ODin | Tube / pipe ODmm | Thread | Threads/in (TPI) | Pitchmm | Nominal ODmm | Male thread, typical reading rangemm | Face O-ring (AS568) |
|---|---|---|---|---|---|---|---|---|
| -4 | 1/4 | 6.35 | 9/16-18 UNF | 18 | 1.411 | 14.29 | 13.92–14.29 | -011 |
| -6 | 3/8 | 9.53 | 11/16-16 UN | 16 | 1.588 | 17.46 | 17.19–17.46 | -012 |
| -8 | 1/2 | 12.7 | 13/16-16 UN | 16 | 1.588 | 20.64 | 20.36–20.64 | -014 |
| -10 | 5/8 | 15.88 | 1-14 UNS | 14 | 1.814 | 25.4 | 24.97–25.4 | -016 |
| -12 | 3/4 | 19.05 | 1-3/16-12 UN | 12 | 2.117 | 30.16 | 29.83–30.16 | -018 |
| -16 | 1 | 25.4 | 1-7/16-12 UN | 12 | 2.117 | 36.51 | 36.18–36.51 | -021 |
| -20 | 1-1/4 | 31.75 | 1-11/16-12 UN | 12 | 2.117 | 42.86 | 42.53–42.86 | -025 |
| -24 | 1-1/2 | 38.1 | 2-12 UN | 12 | 2.117 | 50.8 | 50.46–50.8 | -029 |
Chart notes
- Sealing is by an O-ring in the groove on the male part's face, compressed against the flat face of the female part; the thread only holds the joint.
- ORFS threads differ from the JIC thread of the same dash size (e.g. -8: ORFS 13/16-16, JIC 3/4-16). The same thread can correspond to a different dash size in another system: 1-3/16-12 is both JIC -14 and ORFS -12, and 9/16-18 is both JIC -6 and ORFS -4. The thread alone does not determine the fitting type; check for the flat face or the 37° cone.
- ORFS sizes -14 (1-5/16-12) and -32 (2-1/2-12) are not included in this chart; confirm them separately if needed.
- Face O-rings are AS568 -011 … -029 (1/16" cross-section).
Reference standards
- SAE J1453
- O-ring face seal fittings
- ISO 8434-3
- O-ring face seal fittings (ORFS)
- ASME B1.1
- Unified inch screw threads (UN, UNF)
Values are nominal; for critical applications, verify against the current standard and the manufacturer's catalog.
Description
Description
On ORFS (O-ring face seal; SAE J1453 / ISO 8434-3) connections, the seal is made by an O-ring in a groove on the flat face of the male part being compressed against the flat face of the female part; the thread only holds the joint. For each dash size from -4 to -24, the chart gives the tube OD, UN/UNF thread, pitch, nominal and typical measured major diameter, and the face O-ring number.
How to read the chart
The dash number gives the tube OD in sixteenths of an inch: -8 = 1/2" (12.7 mm) tube. Each dash size has a matching thread: 9/16-18 UNF for -4, 13/16-16 UN for -8, 1-14 UNS for -10, 1-7/16-12 UN for -16. The typical reading range is the value to expect with a caliper on a male thread; 20.36–20.64 mm for -8. Face O-rings are given by AS568 number and have a 1/16" cross-section: -011 for -4, -014 for -8, -021 for -16.
Telling ORFS from JIC
ORFS threads differ from the JIC thread of the same dash size, but the same thread can correspond to a different dash size in the two systems: 9/16-18 UNF is both ORFS -4 and JIC -6, and 1-3/16-12 UN is both ORFS -12 and JIC -14. So don't decide by the thread alone. If the male end has a flat face with an O-ring groove, it is ORFS; if it ends in a 37° cone, it is JIC. On the female side, ORFS has a flat sealing face, while JIC has a 37° conical seat.
Measuring tips
ORFS threads are parallel; you can measure the diameter at any full thread. Watch out for nearby metric threads: 9/16-18 UNF (14.288 mm) and M14×1.5, 11/16-16 UN (17.463 mm) and M18×1.5, 13/16-16 UN (20.638 mm) and M20×1.5, and 1-7/16-12 UN (36.513 mm) and M36×2 measure close to each other with a caliper. The difference between 16 TPI (1.588 mm) and a 1.5 mm pitch, and between 12 TPI (2.117 mm) and a 2.0 mm pitch, is 5.8%; use a pitch gauge to tell them apart.
Where is ORFS preferred?
An elastomer O-ring face seal is known as a solution that holds its seal better than metal-to-metal cone connections on high-pressure, high-vibration lines. That is why it is common on construction machinery, in mobile hydraulics and on lines subject to pressure shocks.
On stainless steel ORFS assembly
Seat the O-ring fully in its groove and lightly lubricate it with an oil compatible with the fluid so that it doesn't fall out during assembly. Replace the O-ring whenever a joint is taken apart. A scratch on the face is a direct leak path; store parts with caps on. The O-ring material is chosen to suit the fluid and temperature; NBR 90 is the common default. ORFS sizes -14 and -32 appear in some catalogs but are not included in this chart; if you need them, ask us after confirming the size.
FAQ
Frequently asked questions
If your question isn't answered here, message us on WhatsApp with dimensions or a photo, and our technical team will answer directly.
What is the difference between ORFS and JIC?
JIC seals by metal-to-metal contact of the 37° cones, ORFS by an O-ring on the flat face of the male part. The threads differ for the same dash size (at -8, JIC is 3/4-16 and ORFS is 13/16-16). A thread can belong to both: 9/16-18 UNF is both JIC -6 and ORFS -4; the face of the fitting tells them apart.
What are the ORFS O-ring sizes?
Face O-rings are given by AS568 number and have a 1/16" cross-section: -011 for -4, -012 for -6, -014 for -8, -016 for -10, -018 for -12, -021 for -16, -025 for -20 and -029 for -24. The material is chosen to suit the fluid and temperature; NBR 90 is the common default.
Where is ORFS preferred?
An elastomer O-ring face seal is known as a solution that holds its seal better than metal-to-metal cone connections on high-pressure, high-vibration lines. That is why it is common on construction machinery, in mobile hydraulics and on lines subject to pressure shocks.
Can the O-ring on an ORFS fitting be reused?
It is not recommended. When a joint is taken apart, the O-ring should be replaced, seated fully in its groove and lightly lubricated with an oil compatible with the fluid. Scratches and dents on the face also cause leaks; store disassembled parts with caps on.
From chart to quote
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