The primary purpose of the coolant hole is to deliver cutting fluid directly to the cutting edge during operations like drilling, reaming, or milling. Instead of relying on external coolant nozzles that may not perfectly reach the point of contact, the internal channel ensures a precise and uninterrupted flow right where the heat and friction are generated.
This serves three critical functions:
Heat Reduction: It drastically reduces the extreme temperatures at the tool-workpiece interface, preventing thermal damage to both the tool and the part being machined.
Chip Evacuation: The high-pressure coolant flow effectively flushes away metal chips (swarf) from the hole. This prevents chips from clogging the flutes, re-cutting themselves, and causing tool breakage or poor surface finish.
Lubrication: It reduces friction, which in turn lowers power consumption and minimizes the risk of built-up edge on the cutting tool.
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