How To Identify And Select Hydraulic Threads: A Guide To BSPP, Metric & Other Types

In hydraulic systems, the importance of foreign thread connections cannot be overlooked. They are widely used in port connections, hydraulic hoses, and lubrication fittings. Correctly identifying and applying the right thread type not only ensures proper sealing performance but also builds customer trust and long-term partnerships.

With the global supply chain becoming increasingly integrated, hydraulic components with different international thread standards are now more common than ever. This article provides a systematic overview of the most common foreign hydraulic thread types, helping you identify and select the right thread with confidence.

1. British Threads (BSPP & BSPT)

British threads are mainly divided into two types:

• BSPP (British Standard Pipe Parallel), also known as “G” threads

• BSPT (British Standard Pipe Tapered), also known as “R” threads

Their nominal sizes are measured in inches, while thread density is measured in Threads Per Inch (TPI).

BSPP parallel threads typically use three sealing methods:

1. BS 5200 60° cone seat (similar to NPSM sealing)

2. External sealing elements (bonded seals, O-ring + washer, elastomer seals)

3. ISO 1179 O-ring seal, requiring the correct size O-ring (as specified in SAE J514)

BSPT tapered threads seal on the thread flanks, similar to NPT threads, and are mostly used in low-pressure or non-critical pipework applications.

2. Metric Threads (DIN Standard)

Metric threads are also divided into parallel and tapered types. They are measured by outside diameter and pitch (mm). In the hydraulic industry, the most common thread pitches are 1.0, 1.5, and 2.0 mm.

Metric parallel threads can seal in three ways:

1. 24° tube seat (e.g., Ermeto® fittings)

2. External sealing elements (bonded seals, O-ring + washer, elastomer seals)

3. ISO 6149 O-ring seal, which only works with the correct size O-ring

Metric tapered threads are commonly used in low-pressure and lubrication applications, sealing on the thread flanks similar to NPT threads.

3. Japanese Threads (JIS Standard)

JIS threads are almost identical to British threads in size, pitch, and thread count. The main difference is that JIS threads feature a 30° outward flare, similar to the 37° flare found in JIC fittings.

This type of thread is widely used in hydraulic systems that follow Japanese Industrial Standards (JIS).

4. Komatsu Threads

Komatsu threads are a hybrid design that combines metric pitch with the JIS 30° flare structure. They are used exclusively in Komatsu machinery.

When identifying this type of thread, it is recommended to also confirm the brand and equipment type, as they are unique to Komatsu applications.

Professional Tips for Identifying Hydraulic Threads

To correctly identify foreign hydraulic threads, you need to consider:

• Dimensional standards (inch vs. metric)

• Sealing method (cone seat, O-ring, external gasket)

• Equipment source and application scenario

Providing complete application details during procurement or repair will significantly improve accuracy in selecting the correct thread fittings.

Why Choose Blince Hydraulic

With over 30 years of expertise in hydraulic thread technology, Blince Hydraulic partners with world-class fitting suppliers to deliver high-reliability solutions and professional support.

If you need foreign thread fittings, adapters, or hydraulic components, please fill out our online inquiry form for fast response and expert consultation.