No cutting tool works well across all conditions. The window exists due to:
( V_c = 180 - 260 , m/min ) ( f_z = 0.08 - 0.15 , mm/tooth ) ( ap \leq 1.5 \times D ) (axial), ( ae \leq 0.5 \times D ) (radial) cutting tool windows
Here is an essay exploring this concept. No cutting tool works well across all conditions