The course of the mechanisms which lead to failure in deformation by bending and the effects of sheet thickness and material properties were investigated. During bending the material breaks down from the stretched outer surface inwards, whereby on the outer surface, through the combined influence of two separate zones of shear, ductile notches form from the base of which shear cracks start. The smallest possible bending radius must be increased more than proportionally to sheet thickness. Over-all, the bendability is similar in its dependence on sheet thickness and strength to reduction in area. Reduction in thickness, necking elongation and crack opening are suitable reference properties for bendability; proportional elongation and hardening exponent are not very suitable.