Mechanical Tube Dimensions and Specifications Table

　　Mechanical tubing refers to tubing used to bear mechanical loads, transmit power, or form mechanical structures—such as drive shafts, hydraulic cylinder barrels, machine tool frame support tubes, bearing sleeves, and ball screw bushings. Its key difference from pressure piping is that mechanical tubing prioritizes mechanical properties, dimensional accuracy, and surface quality, rather than necessarily designing wall thickness based on internal pressure.

　　Shengtian Group explains real-world mechanical tube dimensions, ASTM specifications, tolerance ranges, manufacturing methods, and practical selection advice used by global buyers and engineers.

　　Common Mechanical Tube Standards

　　ASTM A513 Mechanical Tubing covers electric-resistance-welded carbon and alloy steel mechanical tubing. This specification remains widely used in automotive, agricultural, and structural manufacturing.

　　ASTM A519 Seamless Mechanical Tube covers seamless carbon and alloy steel mechanical tubing.

　　SAE J524 and SAE J525 Tubing SAE standards are commonly used for hydraulic and transportation systems.

　　Mechanical Tube Size Chart

　　Dimensions – Mechanical and Structural Rounds

　　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.

　　Material specification

　　Grade 355 Tubes, also commonly known as Structural Hollow Sections, was launched in February. Previously Grade 300 Tube, launched in June 1997, was available. Engineers can now use an increase minimum yield stress of 355MPa yield and an Ultimate yield tensile stress of 450MPa for designs.

　　Grade 355 Tube will enhance the benefits of Structural Hollow Sections and then will allow Tubes to compete on an equal footing with other steel sections.  Furthermore it will assist Tubular steel in competing with other construction materials.

　　Chemical Composition – Maximum

　　Carbon Equivalent – 0.39

　　Carbon – 0.22

　　Mn – 1.6

　　Si – 0.25

　　Mechanical Properties – Minimum

　　Yield Strength – 355MPa

　　UTS – 460MPa

　　Elongation – 20%

　　Standard Lengths

　　Structural and Mechanical tube is stocked in standard lengths of 6 metres, exceptions are:

　　193.7mm round in thicknesses of 3.5 and 6.0 mm where the stocked lengths are 6.1.

　　219mm round in a thickness 3.5 mm where the stocked length is 6.1 metres.

　　219mm round in thicknesses of 4.5 and 6.0mm where the stocked lengths are 6.1 and 9.144 metres.

　　Selected sizes in the structural tube range are available in 9.144 metre lengths.

　　Other lengths may be supplied on request, but are subject to minimum order quantities.

　　Mechanical Properties:

　　Mechanical Tube is more than just steel tubing. In many industries, it directly affects machining accuracy, structural stability, and equipment lifespan. Choosing the right size, tolerance, and manufacturing method helps improve production efficiency, reduce material waste, and ensure more reliable long-term performance. As industrial standards continue to rise, high-precision mechanical tubing has become an essential part of modern manufacturing and engineering projects Email : pipe@stpipefitting.cn.