An accessory for a power tool includes a mounting interface for detachably mounting the accessory to a clamping device of the power tool. The mounting interface is configured to permit the accessory to be used with a wide variety of clamping devices, regardless of manufacturer. The accessory includes a mounting portion having a spindle slot configured to accommodate a drive spindle of the tool and pin openings that are arranged around the spindle slot. The pin openings are configured to receive pins which are arranged around a spindle of an oscillating power tool. When viewed in a cross section that is perpendicular to the first clamping face, at least a portion of opposed surfaces of at least one pin opening are non-parallel.