The following is my understanding working from the drawing above and accepting that the Designer is correct:
It is obvious that the Sheet Metal ‘C’ shape cut out is oversize compared to the Shaft/Tube and the final Diameters of the Auger.
This is because the ‘C’ shaped Sheet Metal parts are stretched to a specific length of 228.6mm.
The action of stretching will both reduce the effective Outside and Inside Diameters of the ‘C’ shape and wrap it a full 360º around the Shaft.
Use a thin card/plastic cut out ‘C’ profile to verify the above.
This stretching effect can be done with the Cut Metal ‘C’ shapes, but not directly achievable in Software. S3D and Solid Works use a similar MO to produce the Auger.
Create the Body of the ‘C’ shape [shown Yellow below] Components:
In the above ScreenShot the translucent cylinder represents the Diameter and Length, 228.6mm x 228.6mm, of a stretched ‘C’ shape Component.
Note: S3D will not display Dimensions from more than one Plane, therefore the vertical Line on the Cylinder does not present the measurement 228.6mm.
It is not possible to obtain the desired visual result direct from the above ‘C’ shape.
Sketch a New ‘C’ shape with an Inside Diameter to match that of the Shaft, 60.3mm, and an Outside Diameter of 228.6mm. Alternatively Transform > Scale.
In the following 2.5mm thickness was used and this is slightly less than the 3/32" specified.
In Tools > Rotate the Angle used was 360º and the Height 228.6mm: