Precision Carbon steel square tube 30x30x2mm Cold Rolled Tight Tolerance 0.1mm Hollow Section

The word precision in hollow section usually means one of two things: a tight outside dimension, or a tight wall. This 30 x 30 x 2 mm tube is controlled on both, with outside dimension held to 0.1 mm and wall to 0.08 mm, achieved by cold rolling the strip to a slit width tolerance of 0.05 mm and then sizing the finished tube through a set of Turks heads with a mandrel inside.

That level of control costs money, and it is only worth it where the tube feeds an automated process. If the part is welded into a frame and ground afterwards, a standard EN 10239 tolerance is fine. If the part goes into a CNC fixture, is gripped by a robot, or has to slide inside another component with a 0.2 mm clearance, the difference between 0.1 mm and 0.3 mm on the outside dimension is the difference between a running line and a stopped one.

• 0.1 mm Outside Tolerance: Outside dimension held to plus or minus 0.1 mm on both axes, verified on a coordinate measuring machine and reported per lot.
• 0.08 mm Wall Control: Wall thickness measured at four points per length, which keeps weight per metre and crush strength consistent from bundle to bundle.
• Cold Rolled Surface: Smooth, bright, oxide free finish that takes plating and powder coating without a mechanical preparation step.
• Straightness and Twist: Held to 0.5 mm per metre with twist under 0.5 degree in 6 m, which matters on automated feed and cut lines.
• Square Cut Ends: Ends cut on a precision saw with squareness within 0.2 mm, so the part can locate against a datum without facing.
• Batch Consistency: One heat number per production run where the order allows, so hardness and forming behaviour do not shift mid project.

Automated fabrication is where this grade pays for itself: machine guards and covers, sensor brackets, robot end effector frames, linear motion carriages, packaging machine parts, display hardware and instrument housings. It is also used in furniture where a visible joint has to close to a fine gap, and in electrical enclosures that must meet an ingress rating. In each case the tube is an input to a controlled process, and the tolerance is part of the design rather than an aspiration.

Precision tube is packed to protect the surface as well as the dimensions: bundle limit 1.5 tons, plastic end caps on every length, interleaved paper between layers, three steel straps over soft packing, waterproof paper and PVC sleeve. Bundles are marked with heat number and dimensional report reference. Mill test reports and a CMM dimensional report are supplied with each lot, and we recommend a trial length before a production order on any new drawing.

One honest warning: if the drawing shows a 0.1 mm tolerance and also calls for hot dip galvanizing after fabrication, the zinc build up alone is 60 to 120 microns and will destroy the tolerance. Specify pre galvanized or plated material, or open the tolerance to 0.3 mm, otherwise the part will not fit after coating.