Orbital drilling kinematics

In orbital drilling the tool (special end mill) moves relative to the work piece on a helical course. Because of the three-dimensional tool path and the superimposed rotary cutting motion a complex machining motion results which determines the contact conditions of the tool. The objective of this study is to describe mathematically the occurring cutting conditions over the engagement angle as a function of the technology parameters: bore diameter, tool diameter and the gradient of the helical course. On the basis of this mathematical description further fundamental and qualitative statements regarding the cutting process of orbital drilling can be determined. The theoretical description confirmed a change of the cutting characteristic over the penetration engagement angle of the tool from drilling to milling.