Thin Gauge Coil Tolerance and Flatness a Buyers Checklist

Thickness Varies Across the Width Not Just Along It

A coil can measure perfectly at both edges and still be out in the middle. In a progressive die that shows up as uneven bottoming and inconsistent part height. Ask for thickness across the width, not a single reading.

Coil Set and Crossbow

Strip remembers the radius it was wound at. At 1 mm it flattens under its own stiffness; at 0.1 mm it does not, and the leading end goes into the die with a curve in it. This is why thin gauge coil often needs a levelling pass that thicker material does not.

Edge Wave and Centre Buckle

Both come from uneven rolling: edge wave when the edges are longer than the centre, centre buckle when the reverse is true. At thin gauge, either will feed unevenly and can jam a high speed line. They are also much easier to see on the strip than to fix once you have it.

Burr Height Matters More as Gauge Drops

A burr that is a small fraction of a 1 mm strip is a large fraction of a 0.1 mm one. At the thin end it affects stacking, feeding and how the part seals. Specify the edge condition rather than assuming it.

Say What the Line Actually Requires

The useful information on an enquiry is the process, not just the tolerance. A high speed progressive die, a roll former and a hand fed press have very different tolerance for shape. Telling us which one it is lets the mill be chosen accordingly.