The orbital drilling process is a very complex machining operation. Due to the helical path of the tool in the material and the tool geometry that can be very complex, the geometry of the chip is very variable along the cutting edge and during a revolution of the tool. This complexity leads to variable cutting forces during drilling and makes it difficult to model and estimate for different tool geometries. The aim of this study is, therefore, to use a modelling of the orbital drilling process in order to study the influence of the geometry of the tool and the cutting conditions on the cutting forces. The final objective is to identify their impact on the quality of the drilled hole and, thus, to control the final quality. First, the chip geometry is modelled from the cutting parameters and the macro-geometry of the tool. It needs to determine the tooth trajectory into the material for each point of the cutting edge. Cutting force models, based on the instantaneous chip thickness, are then implemented. An experimental study validates the modelling by cutting force measurements carried out during orbital drilling tests. From this modelling, it is now possible to study the influence of the geometry of the cutting tool on the forces in order to control the loading on the tool and therefore the final quality of the drilled hole.Read less <