AI CAD prompt: Stepped shaft coupling prototype

Create a new owned Nora3D part document. Use millimeters, world XY as the base and +Z as height. Retain named native features and expose only the controls listed below.

1. Create **Main body**, radius 16, height 50, initially along +Z, with its base center at (0, 0, 0).
2. Create **Lower collar**, radius 19, height 7, initially along +Z, with its base center at (0, 0, 0).
3. Create **Upper collar**, radius 19, height 7, initially along +Z, with its base center at (0, 0, 43).
4. Unite **Main body**, **Lower collar**, **Upper collar** as **Coupling blank**. Require one connected result.
5. Create **Lower shaft**, radius 4, height 22, initially along +Z, with its base center at (0, 0, 0).
6. Create **Upper shaft**, radius 5, height 24, initially along +Z, with its base center at (0, 0, 28).
7. Create **Lower lock**, radius 1.6, height 23, initially along +Z, with its base center at (0, 0, 12).
8. Rotate the current **Lower lock** solid 90 degrees around world Y through [0, 0, 12]. Resolve the actual current entity ID before the operation.
9. Create **Upper lock**, radius 1.6, height 23, initially along +Z, with its base center at (0, 0, 38).
10. Rotate the current **Upper lock** solid 90 degrees around world Y through [0, 0, 38]. Resolve the actual current entity ID before the operation.
11. Create **Screw head relief 12**, a 5 × 8 × 8 box, centered at X=16, Y=0, with its bottom at Z=8.
12. Create **Screw head relief 38**, a 5 × 8 × 8 box, centered at X=16, Y=0, with its bottom at Z=34.
13. Create **Top washer**, radius 7, height 3, initially along +Z, with its base center at (0, 0, 47).
14. Subtract **Lower shaft**, **Upper shaft**, **Lower lock**, **Upper lock**, **Screw head relief 12**, **Screw head relief 38**, **Top washer** from **Coupling blank**, consuming the tools; name the result **Stepped coupling**.

## Public controls

| Control | Default | Range | Step | Meaning |
| --- | ---: | --- | ---: | --- |
| Lower shaft socket radius | 4 | 3–5 | 0.1 | Radius of the lower 22 mm deep shaft socket. |
| Upper shaft socket radius | 5 | 4–5.5 | 0.1 | Radius of the upper socket below the 3 mm washer recess. |
| Top washer recess radius | 7 | 6–8 | 0.1 | Washer recess above the fixed 10 mm upper shaft socket. |

All unlisted dimensions, topology and feature order remain fixed. Radius controls are radii, not diameters. These are independent numeric ranges; do not introduce unsupported formula bindings or assume a fit standard from an example value.