Choosing the Right Hydraulic Fittings

If you work with hydraulic systems long enough, you’ve probably heard it before:

“These two fittings look the same… so they should work, right?”

As fluid power experts, we don’t just build bespoke hydraulic hose assemblies and kits for OEMs — we also supply hydraulic fittings and components as part of complete hydraulic solutions. For years, we’ve supported everyone from large manufacturers to local servicemen and repair shops across the West Midlands. And one of the most common questions we’re asked is this:

"Which fitting is ideal for my application and why is one fitting better than the other?"

It’s a fair question. Many fittings look similar, they often thread together, and on the surface it can feel like overthinking a small component. But in reality, one small fitting choice can make or break the performance, reliability, and lifespan of an entire hydraulic system. Our goal with this guide is to help you understand why that is — and how to choose correctly.

The Real Problem: Same Threads, Different Seals

One of the biggest misconceptions with hydraulic fittings is assuming that if the threads match, the fitting will seal properly. In practice, most fittings are designed to seal in very specific ways — and those sealing methods are not interchangeable.

When incompatible fittings are mixed, the result is often:

• Persistent leaks

• Rework and downtime

• Damaged ports or components

• Shortened system life

  
  

Let’s break down some of the most common fitting types and how they actually seal.

Common Hydraulic Fittings and How They Seal

1. DIN 24° Cone (Deutsches Institut für Normung)

DIN 24° cone hydraulic fittings are widely used on European OEM equipment and metric hydraulic systems. These fittings seal using a conical cutting ring that compresses and bites into the tube as the nut is tightened, creating a strong metal-to-metal seal.

Threads: Metric

Sealing method: 24° cone with cutting ring

Best suited for: European hydraulic systems, OEM machinery, high-pressure applications

Key benefit: Strong, repeatable seal when correctly assembled

Common issue: Incorrect torque can lead to leaks or tube damage

2. JIC 37° Flare (Joint Industry Council)

JIC hydraulic fittings use a 37° flare to create a metal-to-metal seal and are commonly found in industrial and mobile hydraulic applications. They are popular due to their durability and ease of servicing.

Threads: UNF (straight thread)

Sealing method: 37° metal-to-metal flare

Best suited for: Industrial hydraulics, mobile equipment, agricultural machinery

Key benefit: Reusable and easy to maintain

Common issue: A damaged flare will result in leakage

3. NPT (National Pipe Taper)

NPT hydraulic fittings seal through tapered threads combined with thread sealant. While still widely used, particularly in North American and legacy hydraulic systems, they are less resistant to vibration than modern sealing methods.

Threads: Tapered (60°)

Sealing method: Thread interference with sealant

Best suited for: Legacy systems, low-vibration hydraulic applications

Key benefit: Widely available and familiar

Common issue: Poor vibration resistance can cause loosening and leaks

4. BSPT (British Standard Pipe Taper)

BSPT hydraulic fittings rely on tapered threads to seal as they tighten into the port. They are commonly used in lower to medium pressure hydraulic systems.

Threads: Tapered

Sealing method: Thread interference

Best suited for: Low to medium pressure hydraulic systems

Key benefit: Simple installation

Common issue: Overtightening can crack ports or housings

5. BSPP (British Standard Pipe Parallel)

   
   

BSPP hydraulic fittings use parallel threads and require a bonded seal or washer to create a leak-free connection. The threads themselves do not provide the seal.

Threads: Parallel

Sealing method: Bonded seal or washer

Best suited for: UK and European hydraulic systems

Key benefit: Reusable when paired with the correct seal

Common issue: Attempting to seal on threads will result in leaks

6. ORFS Hydraulic Fittings (O-Ring Face Seal)

ORFS hydraulic fittings are designed for high-pressure and high-vibration environments. These fittings seal using an O-ring on a flat face, offering excellent leak resistance.

Threads: Straight thread

Sealing method: Elastomeric O-ring face seal

Best suited for: High-pressure hydraulic systems, vibration-prone applications

Key benefit: Superior leak prevention

Common issue: Damaged or missing O-rings will compromise sealing

Why Correct Hydraulic Fitting Selection Matters

Selecting the correct hydraulic fittings is critical to system performance, safety, and longevity. While many fittings will physically screw together, mixing different thread types or sealing methods often leads to leaks, premature wear, and costly downtime.

Understanding how each hydraulic fitting seals — and where it should be used — helps ensure reliable performance and reduces maintenance issues over time.

Our hydraulic stock management and inventory replenishment service is designed to keep critical parts available without tying up unnecessary capital. As a trusted hydraulic fittings and components supplier in the West Midlands, we support OEMs, service engineers, and repair shops with managed hydraulic inventory solutions, including on-site stockholding and bin fill support.

For teams looking to build in-house knowledge, we also offer BFPA-approved hydraulic fittings identification training to help engineers specify and select the correct fittings with confidence.

By combining local availability with expert product knowledge, we help reduce downtime, simplify procurement, and ensure consistent access to the right hydraulic fittings and components — exactly when they’re needed.