When sheetmetal is bent it never follows a sharp or exact bend. The outside of the bend stretches and the inside compresses. The curvature along the bend is called the bend radius. All materials have a minimum bending radius below which the bend may weaken the metal. Thicker metal has a larger bend radius, and thinner metal has a smaller bend radius (unless it’s harder and more brittle, in which case you may need a larger bend radius to retain the metal’s strength and keep it from splitting). Also, if you bend with the grain of the metal a larger bend radius will result in a stronger component.