PURPOSE: To easily obtain desired spring reaction force and the rough constant load characteristic by providing an edge part so as to be folded toward the axial direction uniformly over the total circumference in internal peripheral and peripheral parts, in the case of a bored leaf spring used for tool clamping of machining center or the like.

CONSTITUTION: In a board disk-shaped leaf spring, an edge part 4 in the internal periphery and an edge part 5 in the periphery are provided by folding an internal peripheral part 2 of the leaf spring and its peripheral part 3 toward the axial direction uniformly over the total circumference. While a flexing amount is increased by using these leaf springs alternately piled together. The characteristic, in which a change of spring reaction force is generated small for the flexing amount in the vicinity of a point in use, is given. Thus, the desired spring reaction force and rough constant load characteristic are easily obtained.