PURPOSE: To contrive an improvement in working efficiency, by a method wherein a clamping tool is prevented from being lost by mounting the clamping tool necessary for detachment of an edged tool on a power-driven tool and a time to be used for fitting the edged tool is made efficient further.

CONSTITUTION: A washer 12 and annular plate 13 are interposed between a seating face of a hexagonal socket head cap screw 14 and the washer to be clamped and clamped down by a hexagonal bar wrench 15 which is miniaturized and made to lighten. The hexagonal bar wrench 15 is mounted on a power- driven tool by a clip provided on a base after clamping.