A method is disclosed for forming a hem flange in an aluminum alloy sheet during the forming of the sheet into a panel that is intended to be attached to a second panel by hemming. The hem flange is formed by fluid pressure over a small radius tool portion to bend the flange from the sheet material and stretch the flange material below the bend to form a thinned hemline valley in the material. The original bend and thinned valley cooperate during the folding of the flange around the second panel to form a flat pinched hem without cracking or fracturing the flange material.
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