Hydraulic Fitting Thread Chart | Hydraulics Direct (2024)

• Abbreviations
• Introduction
  • Fluid port and connector identification tools
• American Connections
  • National Pipe Tapered Fuel (NPTF)
  • National Pipe straight mechanical (NSPM)
  • JIC 37° Flare (SAE J514)
  • SAE 45° Flare (SAE J512)
  • SAE Straight Thread O-ring (O-Ring Boss)
  • Flareless compression (SAE J514)
  • O-Ring Face Seal (SAE J1453)
  • SAE Inverted Flare (SAE J512)
  • Four-Bolt Flange (SAE J518 and ISO 6162)
  • O-Ring Pilot Threads
• International Connections
  • British Standard Pipe
  • British Standard Pipe Parallel (BSPP)
  • British Standard Pipe Tapered (BSPT))
  • Flat Face Port with British Standard Pipe Parallel Threads (ISO 1179-1)
  • Flat Face Port with Metric Threads (ISO 9974-1)
  • ISO 6149 Metric Port and Stud Ends
  • Metric 600o Cone
  • Metric tube compression (DIN 2353 240 Cone)
  • Japanese Industrial Standard JIS 300 Flare
  • Komatsu 30° Flare (JIS Metric)

Calipers:
Used for measuring inner and outer diameters of threads

Thread Pitch Gauge:
Used to measure the amount of threads per inch, as well as the thread to thread spacing in metric applications.

Accurate measurement of threads

Before you start measuring the threads of your fluid pipe or tube, ensure that they are in good conditions. Distorted or worn out threads can give you inaccurate measurements. After confirming that your threads are in good conditions, measure their diameter and record. An I.D./O.D. caliper is a suitable tool for this. Match the dimensions provided in this guide with your recorded measurements.

It is important to note that your measurements may not accurately match with the values provided in this guide. The slight differences are mainly caused by manufacturing tolerances.

After measuring the diameter of your threads, determine their spacing in threads per inch. In the case of metric connections, measure the thread-to-thread distances. To get an accurate value, ensure that the thread pitch gauge is fitting well on the threads. Record the values and compare your measurements with the figures provided in this guide.

Accurate measurement of four-bolt flanges

Begin by using a caliper to measure the port hole diameter the bolt. Once you make a note of that, measure the distance from center to center of the bolt holes, noting the longest spacing.

Dash numbers

The sizes of tubes and fluid pipes are generally identified by abbreviations known as dash numbers, and are commonly used when ordering parts. When using a dash number to identify a fluid pipe or a tube, the numerator part of the fraction is just used. The denominator (which is always 16) is generally ignored. For example, 8/16" or 1/2" equates to size -8 . Note: dash numbers are nominal.

Trustpilot

Note: Both the NPTF and BSPT connectors appear similar, however the two are not interchangeable.

Note: A NPSM female can seal together with a chamfered NPTF male.

Widely found in hydraulic systems, both the JIC male and JIC female of this connection have a 37º flare seat as well as straight threads. The flare seats of the male and female seal together when the straight threads are joined. The straight threads of the each half hold the connection together mechanically.

Note: While most SAE J514 threads look identical to SAE 45º flare threads, their seating angles do not match.

These connectors are widely found in low pressure applications like refrigerant and fuel lines, as well as automotive piping applications. Both halves have a 45° flare seat, and the threads of the each connector engage together to form a tight mechanical connection, with the seal forming on the 45° flare seat.

Note: SAE 45° Flare connectors are identical to JIC 37° Flare connectors, except for the angles of the seats.

The male half of this connection has a 240 seat with a straight thread. The female has a compression sleeve with a straight thread. Along with the sleeve, a female nut and tube partly form the female connection. With the male half, the seal forms between the 24O seat and the compression sleeve. With the female half, the seal forms between the tubing and compression sleeve. The threads mesh together to form a mechanically strong bond.

Widely used in automotive systems, the inverted flare connection features a machined male connector with a 420 seat, and a flared male tubing with a 450 seat. The female side has a 420 seat that provides a sealing surface. The threads connect together to make a mechanically strong bond.

These are available in two pressure groups: standard (code 61) and high pressure (code 62).

This connection is widely found in automotive and commercial air conditioning applications. Both male and female halves have a pilot (could be long or short), and the seal is made when the O-ring is compressed. Threads tightly mesh together to form a strong mechanical bond.

The male end has a 300 seat, which tapered nose of the female swivel makes the seal with.

Note: Although the male end is comparable to the American National Pipe Straight Mechanical (NPSM) male, they not interchangeable, due to their different thread pitches.

The tapered male connects with a tapered female, with the seal forming in the threads.

Note: Although the BSPT male end is comparable to the National Pipe Tapered Fuel (NPTF), they are not interchangeable, due to their different size and thread form.

The parallel threads make a seal using a number of different rings or washers. The seal forms between the male end, and the smooth flat surface on the female end.

The parallel threads make a seal using a number of different rings or washers. The seal forms between the male end, and the smooth flat surface on the female end.

ISO 261 Metric threads

The male half has an O-ring and a straight thread, while the female half has a machined surface, a chamfer, and a straight thread. The O-ring on the male half compresses on the chamfer of the female port, to make the seal. (The ISO 6149 is the same as the SAE J1926-1O-ring Boss, except the ISO 6149 has metric threads.) The straight threads mesh to form a strong mechanical bond.

The male connector has a 60° recessed cone and a straight thread; the female has a straight thread as well, and a globeseal seat. The seal forms between the recessed cone on the male and the tapered nose of the female. The threads of both halves mesh to form a strong mechanical bond. This connection is common in hydraulic systems.

The male connector has a 240 Cone with a straight thread, while the three female connectors have straight threads with a sealing surface. The seal forms between the cone on the male and the sealing areas on the females.

Fittings are available in two categories: DIN 2353 L (light) and DIN 2353 S (heavy) classes. Each has its own tube sizes and thread dimensions as shown in the following table:

The male half has a 30° seat with a straight thread, while the female has a 300 seat with a straight thread as well. This connection and the 37° Flare are alike, however it's 30° seat and BSPP-like thread dimensions make it different from the American 37° Flare.

This connection has parallel metric threads with a 30° seat, and is common on Komatsu equipment. While the JIS metric connection and the JIS 300 flare are alike, the latter has BSPP-like thread dimensions.