The part is not perfectly centered in the middle of the graphics window by
There is no guarantee that the model will be perfectly centered in the middle
of the graphics window. For the six orthographic views (Top, Bottom, Right,
Left, Front and Back) the chances are much greater that the model will be
perfectly centered (but still it is not guaranteed).
What is guaranteed is this statement from the documentation for Fit:
Use the Fit command to adjust the center and scale of a view so that all
objects in the view are displayed on the screen.
Notes and References
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