Page 29 - Demo

27GENERAL DRILLING HANDBOOKType of WorkpieceOne of the main factors affecting the chip shape and the possibility of effectively removing chips from the drilled hole is the type of material. With poor chip evacuation the machined surface can be damaged, thus achieving the same surface roughness value in different materials requires different efforts.MaterialFeatures of Chip FormationP - Steel Low carbon steels tend to form long chips.M %u2013 Stainless Steel Difficult chip control.K %u2013 Cast Iron Fragile and quickly breaking chips.N - Nonferrous There is a risk of buildup and chip evacuation.S %u2013 High Temp. AlloysResistance to cutting causes difficult chip formation.H %u2013 Hardened Steel Short chips, no problem with chip evacuation.Cutting ConditionsFeed and cutting speed have a significant impact on the surface roughness.With an increase in feed, the roughness increases. This is explained by the fact that a large layer of metal is removed in one revolution of drill, related to the phenomenon of detachment and breaking of metal particles increases.Changing the cutting speed affects the roughness in different ways. For example, in a certain range of speeds, a buildup forms on the cutting edge of the tool, which contributes to an increase in roughness and the formation of work hardening on the machined surface, then, with an increase in the speed, the buildup phenomenon stops, the temperature in the cutting zone rises and the chips are removed more smoothly, without breaking off the crystals, therefore, the magnitude of the microroughness decreases. surface roughness smooth roughlow high cutting speedsurface roughness smooth roughlow high feed