Coolant through port tools

Each of SCT’s (Scientific Cutting Tools) coolant through port tools has coolant holes to either 3 or 5 of the tool's flutes because having an uneven number helps reduce chatter. Coolant lowers the surface temperature of the cutting zone making our port tools better equipped to deal with the extremely high temperatures that occur when machining a part. Lower temperatures in the cutting zone also make it less likely for chips to stick and through off the geometry of the tool, making for a perfectly balance long lasting tool. 

Source: SCT