You can set the tool used on a rotary surface milling feature to be a fixed B angle.
This example cast part has a 3D Surface feature, shown in red:
The shaft on the front of the part makes it difficult to machine with the default angle.
Using a 4-axis rotary strategy with the default angle, the head of the machine collides with the chuck, at the point marked with a pink arrow:
Using a fixed B-angle tool axis of 45 degrees, the tool tilts over and avoids any collisions:
