veroniquehasson (asker) Dec 20, 2016:

Marge de variation ? In engineering and machining, an allowance is a planned deviation between an exact dimension and a nominal or theoretical dimension, or between an intermediate-stage dimension and an intended final dimension. The unifying abstract concept is that a certain amount of difference allows for some known factor of compensation or interference.
An allowance, which is a planned deviation from an ideal, is contrasted with a tolerance, which accounts for expected but unplanned deviations.

Schtroumpf Dec 19, 2016:

Bonsoir Je ne connais pas le terme approprié en français mais en allemand, on l'appellerait sans doute Biegezugabe. Par analogie avec "machining allowance / surépaisseur d'usinage", c'est peut-être une "surlongueur de pliage" ici ??