The invention concerns a procedure and a device for the substitution of a blade of racla in a system of racle to room associated to a seam applicator for blots some rotating for the press. The invention serves to the shortening of the times of preparation of the machine, in particular in a paint job device. According to the invention this comes obtained for the fact that during the operation of the machine with disengagement of the pressure a usurata blade of racla (2, 3) comes separated from the case (5) of the system of racle to room and a new blade of racla (2, 3) comes inserted in the case (5) for means of fast closings (11). On the case (5) to the respective blade of racla (2, 3) a blade of racla is associated of closing to estate (4), which, for the interval of time of