The cutting forces during milling vary as the tool are not in engagement at all times and the thickness of the chip varies
Apart from the fact that the inserts are not in continuous engagement and the chip thickness varies the tool can also, in some setups, be exposed to chock forces when each cut is initiated, see technical term Conventional and Climb milling.
This means that the actual cutting forces for milling is impossible to calculat. Even the force for turning, where you hava an contunuous engagement, the acutal cutting force is hard to predict.
