Hydraulic Piping Joint Thread Query Chart

The sealing and connection stability in the hydraulic system are inseparable from the appropriate thread selection. This article will systematically introduce the three commonly used thread types of hydraulic piping joints: metric thread, American unified thread and Whitworth thread, and provide a detailed thread query comparison table. It should be noted that when using, it is necessary to check whether the hydraulic tube is worn or deformed, and to check regularly for leakage during use. Like some hydraulic tube joints used for precision tube connection, the integrity of the hydraulic tube is extremely high. When the pipe flange connection is used with the hydraulic piping joint, more attention should be paid to the sealing.

Metric thread

Metric thread is an internationally used thread standard, also known as metric thread. The characteristic is that the pitch is expressed in millimeters (mm) and the thread tooth angle is 60°.

1. Standard system: ISO 724:1993

2. Tooth profile parameters: 60° equilateral triangle, pitch measured in millimeters

3. Marking method: M [nominal diameter] × [pitch] (pitch omitted for coarse pitch) - tolerance zone - direction of rotation - screw length

4. Example: fine thread, pitch tolerance 6g, left-handed, long screw length, M20 × 1.5-6g-LH-L

American thread

Also known as unified thread. In 1864, American Willian Sellers developed the American National Thread (N) with reference to the British Whitworth thread standard system. The two hydraulic tube joint threads are very similar in diameter and pitch series and tolerance. American threads include coarse thread series UNC, fine thread series UNF, extra fine thread series UNEF, and fixed pitch series UN.

1. Standard system: ANSI B1.1

2. Tooth profile parameters: 60° isosceles triangle, pitch is expressed in threads per inch (TPI)

3. Marking method: thread diameter-threads per inch series code-precision grade

4. Example:

Coarse thread series 3/8-16 UNC-2A

Fine thread series 3/8-24 UNF-2A

Extra fine thread series 3/8-32 UNEF-2A

Fixed pitch series 3/8-20 UN-2A

Whitworth thread

Whitworth thread is widely used in British hydraulic systems. The hydraulic tube joint thread generally adopts 55° British non-sealed pipe thread (G), which can achieve a certain degree of self-sealing effect.

1. Standard system: BS 2779

2. Thread profile parameters: 55° dome thread, specially used for pipe sealing

3. Marking method: G[size code][tolerance grade]-rotation direction

4. Example:

Right-handed, non-sealed cylindrical internal thread with size code 2: G2

Grade A, right-handed, non-sealed cylindrical external thread with size code 3: G3A

Grade B, left-handed, non-sealed cylindrical external thread with size code 4: G4 B-LH

Thread pair consisting of right-handed, non-sealed cylindrical internal thread with size code 2 and grade A cylindrical external thread: G2A

Key parameter comparison

Thread specification lookup table (external threads)

Read more: Joint Models of American Seamless Hydraulic Piping or Difference between seamless pipe and seam pipe