The present disclosure provides a tool for fixing an outer collar to a unit having at least one inner hub and a plurality of vanes. The tool includes a connecting interface with a lifting system and an attachment interface for the outer collar. The attachment interface includes a support surface configured to be supported on one face of a flange of the outer collar, a centering surface configured to be inserted into a hole of the flange, and at least one attachment element configured to attach the outer collar. The tool further includes a surface for centering the tool with respect to the unit, a surface for supporting the tool on the unit, and an actuator for adjusting the support surface with respect to the attachment interface.