Controlling Warp in Thin Sheet
薄板变形与翘曲的控制
标签：薄板翘曲, 对称走锤, 木锤收形, 应力释放, 回火
0.5 mm 以下薄铜板打平极易整体翘曲。诀窍是严格左右对称走锤、正反两面锤击量相等，使双向应力抵消。发现边缘上翘，用木锤在平砧上由中心向边缘轻擀收平；若已严重失稳，整板重新退火后在玻璃板上压重物回火定型，再少量补打。
Sheet below 0.5 mm warps easily. The trick is strictly symmetric striking with equal blows on both faces so opposing stresses cancel. If edges curl up, use a wooden mallet on a flat stake to roll them flat from centre outward. If severely unstable, re-anneal the whole sheet, weight it on a glass plate to set, then planish only lightly. ---