Wear Mechanisms of Milling Inserts: Dry and Wet Cutting

There is less literature on wear of milling tools than on wear of turning tools because milling is one of the most complicated machining operations. The intermittent milling action creates mechanical and thermal surges that distinguish milling from single-point machining. A systematic tool life study for face milling inserts was conducted with and without coolant. Workpieces made of 4140 steel were cut by C5 grade carbide inserts under various cutting conditions. The comparison between dry and wet cutting shows that caution should be taken when applying a coolant for milling operations. Special tests should be carried out in evaluating potential coolant candidates. It is not always true that coolant enhances tool life for milling. Wear mechanisms are presented by means of wear maps. Identified wear mechanisms are: micro-attrition, micro-abrasion, mechanical fatigue, thermal fatigue, thermal pitting, and edge chipping.