In machining processes, nearly all the energy used for cutting turns into heat. This heat comes from two main sources during cutting. First, it is generated as the metal deforms to form chips — similar to how bending a thin piece of steel wire repeatedly in your hands makes it warm. Second, heat is created by the friction when the chip slides against the cutting edge — much like how rubbing your palms together quickly produces heat. One of the main roles of cutting fluid is to act as a lubricant, reducing friction and the resulting heat.
Interestingly, about 80% of the heat produced in cutting is taken away by the chips themselves. The rest — roughly 20% — goes into the workpiece and the tool. Coolant mainly helps only with this smaller portion of heat that stays in the machine components.
Because of this, removing chips from the cutting zone quickly is essential. If chips linger around the tool, the heat they carry stays near the cutting area as well. This can shorten tool life, increase temperatures in the workpiece, and lead to thermal distortion or changes in the workpiece’s metal structure.
Heat removal works better when chips are broken into smaller pieces, because these discontinuous chips carry heat away more effectively. By contrast, operations like drilling tend to have poor chip evacuation, especially in deep holes, which makes heat dissipation less efficient.
Key takeaway: clear chips away from the cutting zone as quickly as you can. Doing this increases tool longevity, lowers tooling costs, and results in higher quality parts. While coolant is important, giving priority to efficient chip evacuation is even more effective.