Welding table flatness — why 0.3 mm/m is the standard worth demanding

How flatness is defined

Flatness is given as the maximum deviation from an ideal plane per running metre. "0.3 mm/m" means: place a 1-metre straightedge on the top and no feeler gauge thicker than 0.3 mm will fit between the straightedge and the top. Check whether the supplier's figure is for a "new table at 20 °C" or "after burn-in and cool-down" — the second one is what you'll actually experience.

What the 0.3 vs 1.0 mm/m difference gives you

A 2×1 m frame welded on a top with 1 mm/m deviation can warp by 2–3 mm at the corner once removed. At 0.3 mm/m the same part stays within ±1 mm — the tolerance accepted by suppliers of CNC components, laser parts or furniture elements. Irrelevant for general fabrication, decisive for higher-precision work.

Flatness standards on our tables

In the ATRIBU range, the BASE, OPTIMA and MASTER series hold flatness to 0.3 mm/m — regardless of whether the top is 8, 12 or 15 mm thick. The plasma-nitrided versions — ARMOR (15 mm top) and TITAN (25 mm top) — reach 0.2 mm/m thanks to heat treatment and full-surface CNC machining. If you weld dimensionally critical structures — machine frames, sub-assemblies for CNC or laser components — pick ARMOR or TITAN.

How to check flatness in your own workshop

• A reinforced straightedge of at least DIN 874/1 accuracy class (minimum 1 m long).
• A set of feeler gauges 0.05–1.0 mm.
• Measure along three axes: lengthwise, crosswise and along both diagonals. Take the largest reading.
• Repeatable thermal condition — measure at room temperature after warming the top evenly through a normal work cycle.

Flatness vs. fixture fit

If your System 16 or 28 fixtures don't seat cleanly in the holes — flatness isn't necessarily to blame. More often it's an oversized hole tolerance, a worn bushing or dirt in the seat. Before you file a warranty claim, check the cleanliness of the holes and the geometry of the bolts themselves.