Short answer
In a JIC 37° connection, the primary seal is provided by the mating of matching male and female conical metal surfaces; the thread mainly generates the clamping force. A thread that engages does not show that the conical surfaces match correctly.
Technical explanation
ISO 8434-2 relates to the 37° flared connection family. A JIC connection must not be confused with flared connections of different angles that look similar. Scratches, deformation or dirt on the seating surface can affect sealing. The assembly torque or turns method depends on the size and the manufacturer's design. For this reason, no single torque value is given for all JIC connections; the manufacturer's instructions for the product concerned govern.
Topic-specific checkpoints
| Item | Description |
|---|---|
| Sealing | Matching conical metal surfaces |
| Thread | Clamping and mechanical joining |
| Inspection | Angle, surface damage and cleanliness |
| Assembly | Size- and product-specific instructions |
How is it assessed in practice?
In a leak investigation, first verify that the system is safely depressurized. Then check the threads and the 37° seating surfaces separately. Do not try to compensate for conical surface damage by wrapping tape on the thread. In the order description, write JIC 37°, the size, the male/female gender and the hose side together. The fact that it can engage for a few turns with a connection of another angle is not proof of equivalence. In the case of recurring failure, also investigate whether the routing is placing a side load on the connection.
Original editorial recommendation; not a clause of a standard.
Frequently asked questions
Does wrapping tape on JIC threads solve a leak?
The primary sealing surface of a JIC connection is not the thread. Correct mating, surface condition and the manufacturer's assembly method must be checked first.
Source coverage
-
S019
4 Easy Steps to Identify Hydraulic Threads Parker Hannifin · accessed 2026-10-19 PDF page 1-2: thread identification
-
S072
ISO 8434-2:2007 ISO · accessed 2026-10-19 Abstract; 37-degree flared connectors; forthcoming revision noted