Page 30 - Demo

28 ISCAR GENERAL DRILLING HANDBOOKDrill GeometryDrills, namely such components as major cutting edges geometry, flutes, and drill overhang (length of cutting part) have a direct influence on the surface roughness of the hole.The right selection of major cutting edges geometry will reduce the load created on the drill while drilling and will also ensure optimal distribution of cutting forces, thereby making the drill work more stable which will be reflected in the surface roughness.Flutes geometry ensures efficient chip evacuation preventing damage by chips to the machined hole surface.Minimal tool runout is essential for successful hole drilling. The longer the drill overhangs, the more difficult it is to control its runout, which directly affects the roughness of the drilled hole. surface roughness smooth roughshort long drill overhangTechnological StabilityThe loads arising during machining are transmitted by the tool and tool holder, as well as by the part and device in which it is clamped. The resulting loads are transferred by devices to the assembly units and mechanisms of the machine, due to which a closed technological system machine-tool-part is formed. The rigidity of this technological system is one of the main criteria for the performance and accuracy of the machine under load, thereby ensuring technological stability. Poor technological stability leads to vibrations of the cutting tool and machined part, which affects the roughness of machined surface.CoolantCoolant has a significant effect on the drilling process and the quality of the machined surface, since it facilitates the process of chip formation and evacuation, removes heat from the cutting zone and lubricates the friction surfaces.