Chip thickening in deep-hole drilling

In conventional turning and milling cutting process models, chips are free of external forces after leaving the cutting area. However, in a drilling process, chip flowing is constrained by the drill flute, causing the change of chip shape and drilling forces. In this research, it is found that when drilling deep holes, the chip thickness increases as drilling progresses deeper into the workpiece. It is also found that during a deep-hole drilling process a significant part of the drilling force increase is due to the chip thickening effect. An analytical model was developed to predict the force increase caused by chip thickening. Experiments have been carried out to verify the model.