Each Rotabroach Cutter is provided with a hole through the shank. This allows the flow of coolant through the center of the tool. A good flow of cutting fluid through the tool is important. It cools and lubricates the cutting edge, helps evacuate the chips, keeps the slug from expanding and helps eject the slug. See Hougen's full line of lubricants including RotaMagic Concentrated Cutting Fluid
For Rotabroach Heavy Duty Industrial Cutters: A coolant system capable of delivering approximately 5 GPM at a minimum of 50 PSI is desired. Centrifugal pumps which may deliver a good flow at low pressure usually do not have the pressure capability to maintain the flow once the drill is engaged in the cut. They may deliver only a trickle in deeper holes when the coolant is needed most.
Other machine tool spindle adapters with coolant inducers are available from Hougen.