A drill turning at thousands of RPM inside solid steel has one fundamental problem: the hottest, most violent zone in the entire operation sits at the bottom of a blind hole, exactly where flood coolant cannot reach. Through-coolant drills solve this by turning the tool itself into a pressurised delivery system. Coolant enters through the machine spindle, travels down internal channels inside the drill body, and exits through ports on the flank faces directly behind the cutting lips. How it works: - Coolant is fed through a rotary union in the spindle, typically at 20 to 70 bar, with high-pressure systems exceeding 100 bar - In solid carbide drills, the channels are formed during extrusion of the carbide blank, twisted to follow the helix of the flutes - Fluid exits at the point, absorbs heat at the chisel edge and cutting lips, then reverses up the flutes - That reverse flow physically flushes chips out of the hole rather than relying on flute geometry alone Why it matters: - Conve...