The present invention is generally directed to an assembly for a drug delivery device comprising a first threaded member (50, 50'), a second threaded member (40, 60') with a longitudinal axis and a thread (61), having at least two consecutive portions (62, 63, 64) with different leads. The first threaded member (50, 50') and the second threaded member (40, 60') are adapted and arranged to rotate with respect to one another about the longitudinal axis of the second threaded member (40, 60') during dose setting operation of the assembly, the first threaded member (50, 50') thereby being axially displaced along the second threaded member (40, 60') from a start position to an end position with respect to the second threaded member (40, 60') due to the mechanical cooperation of the first threaded member (50, 50') with the thread (61). According to the invention, a fast portion (62, 64) of the thread (61), having a greater lead than a slow portion (63) of the thread (61), comprises a multi-start thread and the slow portion (63) comprises less starts than the fast portion (62, 64). The invention is further directed to a drug delivery device for setting and dispensing a number of user variable doses of a medicament comprising such an assembly.La presente invención está dirigida generalmente a un ensamble para un dispositivo de administración de fármacos que comprende un primer miembro roscado (50, 50'), un segundo miembro roscado (40, 60') con un eje longitudinal y una rosca (61), que tiene al menos dos partes consecutivas (62, 63, 64) con avances diferentes. El primer miembro roscado (50, 50' ) y el segundo miembro roscado (40, 60') están adaptados y dispuestos para rotar relativamente entre sí alrededor del eje longitudinal del segundo miembro roscado (40, 60') durante la operación de ajuste de dosis del ensamble, el primer miembro roscado (50, 50') es desplazado de ese modo axialmente a lo largo del segundo miembro roscado (40, 60') desde una posición inicial a una posic
