In a FaceBook thread a member asked if there was a simple way to make square outside corners with a V bit running down a profile line. 

Every suggestion provided was to make inside and outside vectors and use the V-Carve toolpath. HIs profile pass had already been cut though. 

The fluting toolpath, using short vectors in each corner can move from the outside top down to the bottom of the V to sharpen the corners as shown here:

Vectors in the corners shown below.

A trick I figured out helping students when I taught. 

4D

I'll add that this works for any angle of corner, and even when two curves meet at corner.  You just have to know where to start the fluting vectors, and that can be found using the offset tool with your profile line.  Using a 90 degree V-bit the offset would be the same amount as the depth of the V cut. 

4D