Viewing a thread - Can someone explain to me hydraulic fitting sizes....

WiReading through this whole thread shows the confusion that exists mainly due to different industries slang terms.

Not to beat the dead horse, but some of this will be reorganized repeats.

Lets start with sizing.

The "dash" sizing is what you are referring to and is what many fittings and hoses go by. It came from the US military after the Aeronautical and Navy agreed on a standard. The standard was and still is called "AN". You won't find AN fittings on your farm though, they are aluminum fittings, generally anodized and used with braided stainless or kevlar hose as well as forms of hard tubing. It is used extensively in aviation and is the choice for almost every motorsport due to its serviceability. Assembling AN hoses is a lengthier process than whipping up a hydraulic hose though.

The AN standard used a 37* Flare that created the seal. Dash sizing is easy to figure out, its simply in 1/16ths. I actually prefer the dash system anyways. Much easier to hear dash 4 or Dash 12 over the than it is to try and distinguish between 1/4 and 3/4. I assume this could partially be why the military chose it.

The fittings we all have on our equipment use the same threads, the same sizing and the same 37* flare as their AN counterparts but are built much heavier. (AN fittings and hose typically aren't rated much over 300psi whereas JIC is rated up to 5,000psi )

JIC stands for Joint Industry Council. Essentially, awhile back, everybody got together and agreed on that style fitting for use in many things, in an effort to make things more "standard".


Below are the most common Hydraulic Fitting styles you will find on a North American machine.

NPT: National Pipe Thread. Known by many names, but the key features are a tapered thread that relys on thread distortion to form the seal. On the newer "improved NPT" fittings the "thread sealer" is acting more as a lube than anything to encourage the threads to deform to each other without error. These fittings generally have a 30* internal taper as well right at the edge when using true Hydraulic fittings. Many people will use black pipe or galvanized pipe instead which can lead to poor results, or expensive repairs. Hydraulic pipe thread pieces are made out of steel. NPT's upside is that it is very simple, very cheap and very common. The downside is that it is not very serviceable. Often times the fittings are rigid making removal and installation difficult. In addition the fittings wear out quickly and loose their ability to seal. They take much more torque to achieve a good seal and take much more time to install due to the need to physically distort the threads.

37* JIC: Probably the most common right alongside NPT. As explained earlier, utilizes male/female 37* flares to create the seal. You will generally find that most hard steel lines have JIC threads, some older ones have NPT though. JIC's advantage's include easier installation due to them generally having a swivel at both ends and being able to run the fitting on the majority of the way by hand. JIC is not very expensive compared to other models but can be considerably higher than NPT. The downside to JIC is that it is very sensitive to overtightening, which many people fail to observe. Most are so used to cranking on NPT fittings that they feel the need to put their weight into a JIC fitting. Proper torques on these fittings are very very low. So low they make special wrenches so you don't over do it. Overtightening will slowly ruin the flare and the fitting becomes useless. There are inserts available that act as a sealing washer though.

45* SAE: This fitting is similar to the 37* in many ways. However it is rarely used in hydraulic systems. Generally it is reserved for Fuel, Oil, and Air systems on vehicles. Semis are full of these fittings. Most are Brass and running under lower pressures. Don't need to worry about it much for hydraulics as you will rarely run into one if ever.

STORB: Straight Thread O-Ring Boss. Sometimes just called O-ring boss, sometimes SAE O-ring, other times O-ring port fittings, and a number of other combonations. The main thing to remember are the key aspects, SAE straight threads, O ring seal on threads. These fittings rely on an O-ring seated in a boss above the threads to seal things up. They are generally used as adapters for going into hydraulic rams, motors, distribution blocks, etc etc. Its not too often that they are crimped directly onto the hose, but there are some cases where this is true. The advantages to STORB are that it is serviceable. O-ring kits are available with the proper o-rings. Another big advantage is that 90* fittings can be oriented in the direction that they are needed if the proper fitting is chosen. Installation is quick, but again these generally are installed to adapt a valve block to JIC or ORFS fitting on the hose.

ORFS: O-Ring Face Seal. These fittins are also called O-Ring Seal, when referring to the STORB fittings O-Ring Boss is generally used. Seal is on the face, Boss is on the threads. Easy to remember. These fittings also have straight threads, but utilize an o-ring mounted in the face of the male fittings to do the sealing. The Females are almost all swivel and have a flat face inside them that mates up to the o-ring to seal. These are becoming more and more popular. Construction equipment is almost exclusively using this style along with split flange. Advantages to this style are its durability. Generally rated for double what JIC can handle, these fittings seal very well. They are serviceable too. Kits are available with the proper O-rings. They install very nicely and are more forgiving if over tightened. Disadvantages to this style are prices and availability. I stock all of them in our shop, but most of the dealers and parts stores around here that do hoses do not stock a full line except for the Parker Store and NAPA. They are the most money out of any of the fittings, mostly due to supply and demand though. These are by far my favorite style of fitting to use if possible.

Code 61/62: These are generally called "Split Flange" fittings because they incorporate two flanges that clamp the fitting into place. Most often these are found on pumps and some large hydraulic rams. Think of the ORFS face and magnify it. These fittings essentially use the same concept just use two flanges to mount them instead of a threaded nut. Advantages are that they can be put in very tight spaces, easy to mount to pumps and such, serviceable, easy to install as well. They are relatively cheap but again, supply demand plays a role which keeps the price up.

Inverted Male Flare: This is one you will only find in power steering and hydraulic brake systems generally. It uses a pipe with an internal flare and a nut that presses on the out edges of the flare to seat it into the port it is going into.



Hopefully that clears up the styles of fittings somewhat. If you need charts on how to measure them to make sure you get the right one there are plenty all over the internet to download, otherwise let me know and Ill post one.


As important as the fittings is the hose. There are many to choose from but making sure you have the proper hose is key. For most farmers purposes 2 wire does most of it. Higher pressure components though will used 4 wire hose and such. Then there are other special hoses too that are sometimes used. Its important to note that as you change hose types, different fittings become incompatible. So if you are mad at the hose guy because he has the fitting you need but he says it wont work with the hose you need, that is why.

Same applies for crimping ends onto old hoses. Most places won't do it, and its in your best insterest not to. If you have to get going and the proper stuff is not available you can try it, but its just temporary. The major issue is incompatibility between hoses and ends. If you have eaton hose, you use eaton ends, etc. The crimp dimensions are very precise, over crimping or under crimping can case more headaches than it is worth. In addition, the hose has already been compromised by a hole in it somewhere which has exposed the internal steel to the elements and started deteriorating it. Its always cheapest to make a new hose in the long run.

Clean hoses count too. Best to use a scallop blade or hydraulic hose saw for cutting the hose as it will leave less debris behind. The only way to truely get the hose cleaned out though is to use a foam gun which shoots a foam pellet through the hose to scrape everything out of it. Not many shops have these. They run $1,000+. The CAT shops do have them though.

Don't forget to orientate your ends correctly too. Know a lot of guys who just crimp two 90's on and say its fine because the hose is long enough they can "twist/flex" it enough to get it one. In reality what you are doing is putting the hose in a pre-loaded state versus relaxed, which leads to premature failure.

Good name brands of Hoses and Fittings are Eaton Weatherhead, Parker, and Gates.

If you can make all your own hoses, its nice. Maybe do them for the neighborhood? Usually what we end up doing. I stock every Eaton Weatherhead fitting style in their "U" series and 100+' of H245 Hose in the following sizes, 04,06,08,10,12 & 16. It ends up being around 300 or so fittings. Also stock 50-100' of 6 different sizes of Kevlar wrap as well as the Oetiker Clamps for clamping it on cleanly. Overall, this inventory ended up costing between 15,000-20,000. Our supplier has a good deal that as long as you buy from them, you get to keep a crimper, the needed dies and as many storage cabinets as needed for a small refundable deposit. I acquired them over the past couple years. Many of them are not on any of our machines, but maybe someday will be. There is nothing I hate more than to have someone come here for a hose and I have to say that we dont have the right ends. In addition, the amount of time and money that setup saves us year round is immense. Its very nice for customizing/building equipment as well.

In the world of hydraulic and pneumatic systems, compatibility between fittings is crucial for ensuring reliable and efficient operations. One such compatibility often observed is the ability of an SAE inverted male 45-degree flare to mate with an SAE inverted female 42-degree flare. This seemingly counterintuitive match has its roots in engineering design principles and practical application.

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The Science Behind the Compatibility

1. Sealing Surface Contact
   The fundamental principle that enables this compatibility lies in the sealing mechanism of these flares. Both rely on the metal-to-metal contact between the male flare (outer cone) and the female flare (inner cone). Despite the 3-degree difference in the angles, there is still sufficient contact surface to create a reliable seal.
2. Material Flexibility and Deformation
   Many fittings are designed with slight flexibility in their materials to enhance sealing. When tightened, the surfaces deform slightly, allowing the 45-degree male flare and the 42-degree female flare to adapt to each other, effectively sealing any potential gaps.
3. Precision Engineering and Tolerances
   Hydraulic fitting manufacturers adhere to strict machining tolerances. These tolerances account for minor mismatches, ensuring that fittings like the SAE 45-degree and 42-degree flares can function together without compromising performance.
4. Historical Design Practices
   Over time, industry standards have evolved to allow some degree of interchangeability among fittings. This was done to ensure broader usability, reduce inventory complexity, and accommodate various application needs without requiring exact matches.

Practical Considerations

While these fittings can work together effectively, it’s essential to remember:

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• Pressure Ratings: Ensure the combined fittings can withstand the operating pressure of your system. Over-tightening or using the fittings beyond their rated pressure can lead to failure.
• Temperature Limits: Check the temperature compatibility of the materials used in the fittings.
• Application-Specific Needs: For critical systems, consult the manufacturer’s guidelines or a professional engineer to verify compatibility and safety.

Benefits of SAE Inverted Flare Compatibility

1. Flexibility: Allows users to connect different systems without needing entirely new fittings.
2. Cost Efficiency: Reduces the need for multiple spare parts in inventory.
3. Ease of Use: Provides more options for retrofitting or upgrading existing systems.

Conclusion

The compatibility between SAE inverted male 45-degree and female 42-degree flares demonstrates the ingenuity of hydraulic fitting design. By leveraging principles like surface contact, material deformation, and precision tolerances, these fittings provide users with versatile and reliable connections. However, it’s always advisable to evaluate the specific application requirements to ensure safety and optimal performance.

Whether you’re upgrading an existing system or designing a new one, understanding these principles can help you make informed decisions and achieve efficient results in your hydraulic systems.

Contact us to discuss your requirements of BSP FEMALE One Piece Hose Fittings. Our experienced sales team can help you identify the options that best suit your needs.