How it connects
Metal-to-metal cone seal: the 45° male nose seats inside the flared tube end (or a female 45° swivel seat), clamped by a flare nut on the 7/16-20 UNF thread. The threads do not seal.
Male and female halves
This is the male half, with an external thread and a 45° cone nose. The female half is the flare nut or swivel nut with internal 7/16-20 thread, holding the flared tube.
Usually connects to
- Matching-size SAE 45° female flare nut over flared copper, aluminum, steel or soft tube, including 1/4 and 3/8 in
- Matching female flare swivel on a gas-appliance connector, hose or adapter
- Matching 1/4 in refrigerant charging/manifold/test hose, sometimes with valve-core depressor
Common sizes
- Named by tube OD, commonly 1/8–3/4 in (-2 through -12), with the series extending to about 1 in.
- Listed pairs: 1/8 → 5/16-24, 3/16 → 3/8-24, 1/4 → 7/16-20, 5/16 → 1/2-20, 1/2 → 3/4-16, 5/8 → 7/8-14 and 3/4 → 1-1/16-14.
- The descriptions give both 5/8-18 and 9/16-24 for 3/8 in tube; confirm the fitting rather than assuming these threads interchange.
Where it is used
HVAC/refrigerant lines and service/manifold portsLP/natural-gas appliancesAutomotive/truck air, fuel and low-pressure linesHydraulic/lubrication linesWater-supply/ice-maker plumbing
Variations
- Flare-to-MIP/NPT or FIP adapter
- Double-male flare union
- Elbow or tee
- Schrader service/access port with valve core, commonly 1/4 SAE
- 5/16 in SAE R410A service port, 1/2-20
- Flare cap/nut
How to recognise it
Usually a brass fitting. It has a short straight thread of about 11.1 mm (0.437 in) major diameter at 20 TPI, ending in a smooth 45° conical nose with a bore for 1/4 in tube. Often paired with a hex and an NPT or second flare end.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| JIC 37° flare | JIC uses the same 7/16-20 thread for -4, but its cone is 37° (steeper-looking, narrower). Check the seat angle with a gauge; 45° is common in brass, 37° in steel hydraulic fittings. Same 7/16-20 thread, but the cone is 37° instead of 45°. JIC fittings are usually steel hydraulic parts, while refrigerant flare fittings are usually brass. They don't seal reliably when mixed. |
| Inverted flare (SAE 45° inverted) | With an inverted flare the male thread is on the tube nut and the seat is inside the fitting body. A standard male flare fitting has an exposed cone nose past the threads. |
| NPT pipe thread | NPT threads are tapered and coarser (18 TPI, about 0.54 in OD). The 7/16-20 flare thread is straight, ends in a smooth cone nose and does not seal on the threads. The flare thread is straight, about 0.4375 in OD at 20 TPI, and ends in a cone. |
| SAE O-ring boss (ORB) -4 | Also 7/16-20, but it has an O-ring groove under a flat face and no cone. |
Also called
-4 SAE 45° flare45° flare male, 7/16-20 UNF1/4 inch SAE male flare; 1/4" flare male (refrigeration)1/4 MFL3/8 in male flare-6 SAE 45° flare; SAE 45° flare male3/8 MFL45° flare 3/8 tube
Good to know
Confirm the flare angle. Brass flare-to-MIP adapters commonly use 45° SAE, but 37° JIC can share the same thread and is a different seat.
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