Abstract: A mechanism for mounting a sanding disk to the spindle of a portable right-angled grinder that will allow the connection to be released without extra tools. The mechanism consists essentially of a hollow spindle (18), of a tensioning anchor (22) that is accommodated inside the spindle (18) such that it can slide back and forth axially subject to an activating mechanism (54) but cannot rotate, and of two flanges that accommodate the sanding disk (28) between them, one of which, a mating flange that constitutes a support (20), is rigidly secured to the spindle, and the other of which, the tensioning flange (26), is loosely secured to the tensioning anchor (22). Between mutually facing demarcating surfaces (34 & 36) of the tensioning anchor (22) and the spindle (18) is a space (39) that communicates with another space (44) in the tensioning anchor (22). The spaces (39 & 44) are full of a plastic material (40) that can transmit force hydraulically.