Mechanical Tube Size Chart

What is Mechanical Tubing?

Mechanical pipes & tubes are steel tubes specially used in industrial fields such as machinery manufacturing, equipment structure, transmission system, etc., with the characteristics of high precision, high strength, wear resistance and pressure resistance. It is different from ordinary construction steel tubes or decorative tubes, and must meet strict dimensional tolerances, material properties and process requirements.

Definition:

It refers to seamless or welded steel tubes used for mechanical structures, hydraulic systems, bearings, shafts and other components, which must meet specific mechanical properties and processing accuracy.

Core features:
High precision: small tolerances for outer diameter and wall thickness (such as ±0.05mm), strict requirements for roundness and straightness.
High strength: The material is mostly carbon steel (A519), alloy steel (such as 40Cr) or stainless steel (such as 304).
Process optimization: Improve surface finish (Ra≤0.8μm) and mechanical properties through processes such as cold drawing, cold rolling and heat treatment.

Main types of mechanical steel pipes:

1. Classification by use
Structural steel pipes: used for mechanical frames, transmission shafts, and supports.
Main standards: GB/T 8162, ASTM A53

Hydraulic/cylinder pipes: used for hydraulic cylinders, cylinder barrels, and precision piston rods
Main standards: GB/T 3639, DIN 2391

Bearing pipes: used for bearing rings and needle bearing jackets
Main standards: GB/T 18254 (special for bearing steel)

High-strength mechanical pipes: used for automotive parts and engineering mechanical arms
Main standards: ASTM A519, EN 10305

2. Classification by production process

Seamless steel pipes: formed by hot rolling or cold drawing, without welds, and strong pressure bearing capacity (such as hydraulic systems).
Welded steel pipes: high-frequency welding or submerged arc welding, low cost, suitable for general structures.

Seamless Mechanical Pipe and Tube Size & Dimensions Chart:

The following is a detailed size table of seamless mechanical steel pipes, covering common types such as structural, hydraulic, and precision machinery.

1. Structural seamless steel pipes
Applicable to general mechanical structures, shafts, brackets, etc., with a wide range of sizes and loose tolerance requirements.

Common dimensions and theoretical weight:

Outer diameter (mm)	Wall thickness (mm)	Theoretical weight (kg/m)	Applicable scenarios
21.3	2.0~4.0	0.95~1.58	Light structure
33.7	2.5~6.0	1.92~4.10	Shaft, support tube
48.3	3.0~8.0	3.36~7.95	Mechanical frame
60.3	3.8~10.0	4.91~12.39	Heavy equipment
88.9	4.0~12.0	8.38~22.77	Construction machinery
114.3	4.5~15.0	12.19~36.74	Large structural parts

Tolerance range (GB/T 8162):
Outer diameter: ±1%
Wall thickness: ±10%~12.5%

2. Seamless steel pipe for hydraulic and precision machinery (DIN 2391/GB/T 3639)
Applicable to hydraulic cylinders, cylinders, high-precision shafts, requiring high dimensional accuracy and high surface finish.

High-precision cold-drawn seamless steel pipe size table:

Outer diameter (mm)	Wall thickness (mm)	Outer diameter tolerance (mm)	Wall thickness tolerance (mm)	Roundness tolerance (mm)
6~30	0.5~3.0	±0.05~±0.10	±0.05~±0.10	≤0.03~0.10
30~60	1.0~5.0	±0.10~±0.20	±0.10~±0.20	≤0.10~0.20
60~120	2.0~10.0	±0.20~±0.30	±0.20~±0.30	≤0.20~0.30

Typical precision steel pipe examples:

Outer diameter (mm)	Common wall thickness (mm)	Theoretical weight (kg/m)
10	1.0, 1.5, 2.0	0.22, 0.31, 0.39
25	2.0, 3.0, 4.0	1.13, 1.63, 2.07
50	3.0, 5.0, 8.0	3.48, 5.55, 8.29
80	5.0, 8.0, 10.0	9.26, 14.20, 17.27

Applicable materials:
Carbon steel: 20#, 45#
Alloy steel: 40Cr, 42CrMo
Stainless steel: 304, 316

3. American standard seamless steel pipe for machinery (ASTM A519)
Applicable to high-strength mechanical structures, automotive parts, aerospace, with a wider range of sizes.

ASTM A519 Common Sizes:

Outer Diameter (inch/mm)	Wall Thickness (inch/mm)	Theoretical Weight (kg/m, Carbon Steel)
0.5" / 12.7 mm	0.065"~0.25" / 1.65~6.35 mm	0.45~1.53
1" / 25.4 mm	0.12"~0.5" / 3.05~12.7 mm	1.69~6.69
2" / 50.8 mm	0.15"~0.75" / 3.81~19.05 mm	4.47~17.06
4" / 101.6 mm	0.25"~1.0" / 6.35~25.4 mm	14.89~47.20

Material:
1020, 1045 (carbon steel)

4130, 4140 (alloy steel)

Read more: Mechanical Tubing vs. Structural Tubing or Cold Drawn Seamless Tube for Mechanical & Hydraulic