Threading Technology – Clamping Technology 520

424 Twist Drills VA STEEL Accessories 3 x D 5 x D 6 x D Tech. Info v c / f Product Finder 8 x D 2-3.5 x D 5.8 Influence of the point angle Standard point angle 140° (EF-Drill) • Stable point • Short chips • Good centering • Reduced power consumption • Reduced torque • Formation of slug • Minimal burr formation • Long tool life Point angle 118° • Unstable point • High torque • High power consumption • Unstable primary cutting edges • Slug formation very much reduced • Formation of burr during the exit of the drill 5.9 Reduce feed on angled entry / exit surfaces The EMUGE double margin design provides excellent guiding ability that is especially effective in work with transverse holes or angled exits. The EMUGE EF-Drill self-centers primarily by means of the chisel edge. With slanted, concave, convex or very rough entry surfaces, the tool is being deflected. That is why feed must be reduced in the first drilling stage. Angled entry surfaces Angled or rounded exit surfaces Feed must be reduced during the first drilling stage: • DIN 6537 short (3 x d 1 ) 1…2°: by 20% 2…3°: by 40% 3…4°: by 50% 4…5°: by 70% • DIN 6537 long (5 x d 1 ) < 1°: by 30% 1…2°: by 40% 2…3°: by 50% >5° Feed must be reduced during the breaking through stage: • For EF-Drill with single margin by 70% • For EF-Drill with double margins by 50% 5.10 Proper edge preparation (honing) Every drill has an edge preparation (hone) which is in relation to the drill diameter and material to be cut. The edge preparation is for stabilizing the cutting edge. The feed is in relation to the edge preparation and material. Good feed Too low feed