JIC Fittings & The SAE J514 Standard
Figure 1: JIC hydraulic fittings find their use in many different areas, including agricultural equipment.
While searching for hydraulic fittings you will often see the names AN fittings, JIC fittings, SAE/ISO fittings, and flared fittings used interchangeably. As we can see in our article about AN and JIC fittings all these fittings have the same basic design. This article covers JIC pipe fittings, now more commonly known as SAE/ISO 37° flare fittings.
Table of contents
- JIC fittings
- Design of JIC 37° flare fittings
- 37° flare fitting installation
- Pros and Cons of using JIC Fittings
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Before WWII, the American Air Force developed a fitting, now known as the 'AN' fitting, which had a 37° flare angle. The threads on this fitting were precision 3A/3B thread type. Most branches of the U.S. military, as well as general aviation and commercial aviation, used 'AN' fittings from the 1930s to the 1960s. The fittings were even used by the US Military in several land and sea applications, giving rise to confusion between these and their industrial counterparts, the SAE 37° industrial standard fittings.
Many types of 37° flare fittings have been introduced into the industrial market following the end of World War II, creating a nightmare for users. An organization of manufacturers, the Joint Industry Conference (JIC), decided to standardize on the AN' design, except with a 2A/2B thread class to make manufacture easier. Around the world, these fittings came to be known as 'JIC' fittings. They wanted the fitting standard to have the reputation of SAE. SAE International is a global association of more than 100,000 engineers and related technical experts in the aerospace, automotive and commercial-vehicle industries. SAE was persuaded to take on the task, and they assisted in the development of the standard. As a result, the SAE standard 37° flare fitting became part of SAE J514 in 1950. In 1986 these fittings became an ISO standard, ISO 8434, which was replaced by ISO 8434-2 in 1996.
Design of JIC 37° flare fittings
37 degree flare fittings can be used with either inch or metric tubes. The male JIC fitting mates up to a 37° flared tube or female flare fitting. A small metal-to-metal sealing surface between the nose of the fitting and the flared tube or internal flare of the female fitting makes a seal when connected. The relatively small seal area makes for a compact design, while JIC fittings have the benefit of a low assembly torque, and high temperature and high pressure capability.
Figure 2: An example of connecting a male and a female JIC fitting. The male 37° flare matches up with the female flare to provide a tight metal to metal seal.
37° flare fitting installation
Trouble-free operation of JIC fittings depends on proper installation. Not only will it prevent leakage of valuable hydraulic oil or gas, improper installation could also lead to damage to the threads and fittings, leading to additional costs.
There are three steps to installing JIC fittings in such a way that the end result is a leak free, well functioning connection.
- Cutting, deburring, and cleaning of the tube
- Flare inspection
Cutting, deburring, and cleaning of the tube
Read our article about tube cutters to learn the correct procedures for tube cutting, or watch the below youtube video:
When installing new tubing on your system the use of a hydraulic flaring tool is more than useful. These tools require little force from the operator and produce uniform flares on tubing, ensuring leak free connections when used with 37° flare fittings.
For JIC fittings the recommended installation method is the Flats From Wrench Resistance. This method is a relatively simple way of ensuring there is sufficient torque on the connection, without damaging the fitting or the thread. For this example, we will connect a flared tube with a female connection to a male bulkhead mounted fitting. Follow the steps below to tighten the JIC hose fittings correctly:
- Align the tube and male and female connectors and tighten with a wrench until you feel a slight resistance (about 30 in.lb or 3.39 Newton Meter). This point is the Wrench Resistance position.
- Mark this position on both the male and the female connection.
- From this position tighten the nut further according to the amount of flats given in the below JIC fittings chart. A flat is one side of a hexagonal tube nut and equates to 1/6 of a turn.
- Once the nut has been tightened with the required amount of flats mark the both the female and male connections again. This will give a secondary reference point to check tightness of the connection over time and give a marker for reconnecting after maintenance.
Using the flats method allows installation without the effects of plating, lubrication and surface finishes that influence torque required for tightening.
Table 1: Sizing chart
|Tube Outer Diameter (mm)||Tube Outer Diameter (inch)||SAE Dash Size||Thread Size/ threads per inch||Tube connection FFWR||Swivel nut or hose connections FFWR|
|5/8||14, 15, 16||-10||⅞-14||1 1/2||1 1/2|
|3/4||18||-12||1 1/16-12||1 1/2||1 1/4|
|7/8||22||-14||1 3/16-12||1 1/2||1 1/4|
|1||25||-16||1 5/16-12||1 1/2||1|
|1 1/4||28, 30, 32||-20||1 ⅝-12||1||1|
|1 1/2||35, 38||-24||1 7/8-12||1||1|
|2||42, 50||-32||2 1/2-12||1||1|
Pros and cons of using JIC fittings
When compared to pipe fittings, flared fittings have significantly superior design and performance characteristics and can be used with thin to medium wall tubing. Pipe fittings have long been replaced with flared fittings in most hydraulic design applications, particularly in military and aerospace equipment and are a very common connection type in low to medium pressure applications. There are several advantages to using flared fittings:
Advantages of using JIC fittings
- They are widely available.
- Various sizes, shapes, combinations, and materials are available.
- The sizes are consistent with SAE standard J514, making them interchangeable with fittings from different producers, as long as these adhere to the same standard.
- They are often used in high-temperature applications because they do not have an O-ring.
Disadvantages of using JIC fittings
- In some instances (high vibration applications) they have a lower pressure rating than required.
- Because these seals are metal-to-metal, they are limited to hydraulic, liquid, and non-critical applications.
- Assembly of the 37° flare fittings can cause some nose collapse, which is exacerbated by over-assembly. As a result of this nose collapse, the flow diameter is reduced.