Abstract: The rotor of a turbomachine has a rotor blade stage formed by sectors which are each secured to a rotor drum by radially inwardly directed, axially spaced flanges on the blade platform of the sector cooperating with radially outwardly directed, axially spaced flanges on the drum. The cooperating downstream flanges of the drum and the blade platform have at least one pair of registering holes through which a cylindrical pin extends, the pin having a radial collar interposed between the two flanges and an annular groove positioned downstream from the collar. The assembly is held in position by scalloped segments which are inserted into an annular groove in the drum on the downstream side of the downstream flange, and which are shifted circumferentially to engage edges thereof in the grooves of the pins before being locked by tongues at opposite ends of the segments.