There are two ways to model this correctly.
First would be to individually cut-revolve the cutter dia at the point of the 90° turn, and then cut-sweep the cutter bottom profile individually to the centerline of the cut revolve.
A better method would be to do this in two individual cut sweeps.
Since the bottom profile of the cutter is a semi-circle, you need to cut-sweeep two quarter-circle profiles.
The left side quarter (refereing to the inside on the bend half) is swept along a right angle guide line which is on the top surface and pierces the OD of the arc.
The right side quarter (outer half around the bend) is swept along a right angle guide line with an inclusive sketch fillet radius equal to the ball mill radius which is also on the top surface and pierces the OD of the arc.
Both these methods will produce the correct cutter profile after the cut.
If you want to send you a simple model of this, or need further clarification, let me know.
Good Luck.......
Remember...
"If you don't use your head,
your going to have to use your feet."