Cold-rolled thickness tolerances and flatness acceptance (EN 10131 / ASTM A480)
Thickness tolerances are banded by width and thickness, and flatness is measured as steepness (mm/m). Measure at the specified points against the tolerance class — not just the middle.
Thickness tolerance and flatness are the two key dimensional acceptance criteria for cold-rolled stainless sheet:
1) Thickness tolerance: banded by width and thickness per the standard (EN 10131 / ASTM A480 / GB/T 708); there are also within-sheet thickness variation limits. Measure at specified distances from the edge and at multiple points along the length (head/middle/tail), not just the centre.
2) Flatness: measured as steepness (mm/m) or I-units, covering edge wave, centre buckle and crossbow; cut-to-length sheet also needs cross curvature.
3) Width and length tolerances: per the standard classes; slit strip focuses on width tolerance and burr.
Acceptance advice:
• State the tolerance class (normal/tighter) and flatness limit in the contract.
• Use calibrated micrometers/gauges and record measurement positions.
• For cut-to-length, slitting or stamping, agree tighter flatness and edge requirements.
• In disputes, re-measure at the standard positions rather than by feel.
Missing thickness or flatness targets directly reduces downstream yield — measurement records are worth more than verbal promises.
