Cutter and Insert Position in Face Milling:
The relationships of the cutter diameter to insert angles and their position relative to the surface to be milled is important in that it will determine the angle at which an insert enter and exits the workpiece.
The same insert may engage the workpiece at different angles, depending on the relative positions of the cutter and the workpiece width.
Note in fig. 24.9a that the tip of the insert makes the first contact, so there is a possibility for the cutting edge to chip off.
Note that in fig. 24.9b the first contacts at an angle and away from the tip of the insert, therefore there is lower tendency for the insert to fail, because the forces on the insert vary
more slowly.