Use of a stepped shrink-fit ring to assemble a steering assist motor in a steering case

An assembly method for fastening a first part to a second part, the method comprising:

• interposing a cylindrical assembly ring between the first part and the second apart, the cylindrical assembly ring having a central axis, a radially inner face and a radially outer face, the assembly ring having a first ring segment axially stepped relative to a second ring segment along the central axis, the first ring segment having dimensions different from the second ring segment in a section normal to the central axis;
• press-fitting the radially inner face of the assembly ring on the first part to form a first clamping contact between the first part and the assembly ring, which secures the first part and the assembly ring, the first clamping contact occupying a first interference area on the radially inner surface of the assembly ring;
• and
• press-fitting the radially outer face of the assembly ring on the second part to form a second clamping contact between the second part and the assembly ring, which secures the second part and the assembly ring, the second clamping contact occupying a second interference area on the radially outer surface of the assembly ring, and the first interference area and the second interference area being confined to the respective first ring segment and second ring segment such that the first interference area does not overlap with the second interference area.