The invention provides a clamping system (1) for a rotary tool (70), for example a milling cutter or drill. The clamping system (1) includes a base element (10), a collet (30) and a clamping nut (50), said clamping nut (50) friction-locking the rotary tool (70) within the base element (10) with the collet (30). In order to avoid a relative rotation of the base element (10) and the collet (30), the clamping system (1) has a form locking anti-twist protection which blocks a rotation of the collet (30) relative to the base element (10).

To stably hold a holder by a holding block while improving the workability of an operation of attaching the holder to the holding block. A clamp member includes a pressing portion that, in a state of being interposed between one inner side surface of a groove of a holding block and an upper surface of a holder, presses the holder toward the other inner side surface of the groove. The pressing portion includes a first protrusion that comes into contact with a first inclined surface of a first cutout of the holder, and a second protrusion that is separated from the first protrusion and comes into contact with a second inclined surface of a second cutout of the holder.