Mmmm, tricky one as ideally you want the angle of the teeth to increase as you move outwards. If you're cutting with a constant angle cutter would turning each surface to a slightly concave conical section sort the problem I wonder? That way the angle of the teeth is constant but they become wider as you go outwards. Sorry I don't have any 3D CAD here at home to check it out. Alternatively cutting them as a square (or trapezoidal) section with the width increasing radially outwards would do (2 passes for each cut offset by 1/2 the angle) might sort it, but engagement would be more clunky than with triangular teeth.