Thread identification
SAE Code 61 Flange (SAE J518)
Code 61 is the standard-pressure SAE 4-bolt flange connection: an O-ring in the flange head compressed against a flat pad by split flange clamps. It's how larger hose connects to pumps and motors without wrestling giant threads.
Identify it
Four checks at the bench.
- 01
Four-bolt split-flange clamp pattern around a flange head
- 02
Measure flange head OD and match to the code 61 chart
- 03
Code 61 heads are shorter/smaller than code 62 at the same nominal size
- 04
Check port pad bolt spacing against the chart to confirm series
Don't confuse it with…
- Code 62 shares the concept with a thicker head and wider bolt pattern — the two never interchange
- Metric-bolt flange variants (ISO 6162 with M-bolts) look identical; check bolt threads
Reference
Size chart.
| Size | Thread |
|---|---|
| 1/2" (head OD 1.19") | to 5,000 psi |
| 3/4" (head OD 1.50") | to 4,500 psi |
| 1" (head OD 1.75") | to 4,000 psi |
| 1-1/4" (head OD 2.00") | to 3,000 psi |
| 1-1/2" (head OD 2.38") | to 3,000 psi |
| 2" (head OD 2.81") | to 3,000 psi |
A1 stocks it.
- Code 61 Flange Head — StraightA1-4S-C61
- Code 61 Flange Head — 90°A1-4S-C61-90
- R13 Interlock Code 61 FlangeA1-6S-C61
- 6-Spiral Code 61 Flange — 45°A1-6S-C61-45
Unsure even after the checks? Bring the fitting to the counter — gauging an unknown thread takes us about a minute. (817) 589-7101.
SAE Code 61 Flange (SAE J518) — FAQs
What's the difference between code 61 and code 62?
Pressure class and dimensions. Code 61 is the standard series (3,000–5,000 psi by size); code 62 is the 6,000 psi series with thicker heads and different bolt spacing. They do not mix.
Why did my flange connection leak after service?
Usually a pinched or reused O-ring, uneven bolt torque, or mixing 61/62 hardware. Torque split flanges in a cross pattern with a fresh ring.