1. Excessive Heat: Heat build up is a major cause of cutting tool edge failure and shortened tool life.
2. Abrasion: is the wearing away of the cutting tool.
3. Chipping/ crumbling of cutting edges: When cutting forces put a greater load on the cutting edges than the tool material can withstand, small fractures in the end mill can result in portions of the cutting edge chipping away.
4.Clogging: The material of some work-piece produces longer, stringy, compressible chips.
5. Built-up Edges:Particles of the workpiece material may cold weld, gall, or otherwise adhere to faces of teeth adjacent to the cutting edges.
6. Hardening of the workpiece: (strain hardening, cold working, or glazing) cutting edges compress or deform the workpiece surface. Changing the material structure of the work-piece- increasing its hardness. Many high alloyed carbon tool steels, high strength superalloys and all austenitic stainless steel are susceptible.
7. Cratering: In the area of high heat & abrasion- the chips can erode a barrow hollow or groove into the tooth face. Once it starts it gets progressively worse until the tool fails.