Mechanical assembly for the transmission of axial forces between at least two rotor parts of a turbomachine and method for producing a variable threading for such an assembly

A mechanical assembly including two rotor parts of a turbomachine, one of the two rotor parts being a compressor shaft, another of the two rotor parts being a turbine shaft, at least one of said two rotor parts having a portion with an outer threading, said assembly further including, for transmission of axial forces between said two rotor parts, a nut with an inner threading able to cooperate with said outer threading to axially block by tightening the other of the two rotor parts relative to the first of the two rotor parts and to allow transmission of axial forces between said two rotor parts, wherein a pitch of the outer threading and/or a pitch of the nut varies/vary along an axial dimension of the threading, a space between a thread of said outer threading and a thread of the nut gradually decreasing from a first thread to a rear thread in an expected direction for the axial force, wherein the thickness of the thread of the inner threading increases along the expected direction for the axial force such that a pitch variation from one thread to another along the axial dimension of the threading is constant, the thickness of the thread of the inner threading being measured along the axial dimension of the threading and the expected direction for the axial force.