Combining several machining operations in a single step is a proven method of increasing production efficiency but, with drilling and boring operations, combining operations produces a high volume of chips that can be difficult to control reliably and discharge efficiently.
In MAPAL’s new spiral-flute step drills, however, these challenges have been fully addressed with a novel spiral-fluted geometry that provides efficient chip transport and ensures that there is no chip congestion, even at the transition from solid drilling to step boring. This means that where separate tools were previously needed for piloting, deep hole drilling and boring, these three operations can now be performed with a single tool as a one-shot operation.
To achieve the enhanced performance of the new drills, MAPAL engineers carefully refined the flute geometry and pitch, as well as ensuring that the chip flutes are polished over the entire length of the drill so as to minimise the friction between chips. In addition, the PCD blades are perfectly embedded into the spiral of the solid drilling and boring step to optimise the drill’s cutting characteristics. These novel design features significantly reduce the amount of heat transferred to the part compared with conventional straight-flute drills.
A further refinement is the optimised positioning of the coolant outlets. This is crucial for MQL machining, where it is essential that the coolant aerosol reaches the points where lubrication is most needed, to reduce the risk of build-up edges and to prolong the life of the drill.