The torque and thrust force in twist drilling—I. Theory

Bone drilling is an essential part in orthopaedics, traumatology and bone biopsy. Prediction and control of drilling forces and torque are critical to the success of operations involving bone drilling. This paper studied the drilling force, torque and drilling process with automatic and manual drill penetrating into bovine cortical bone. The tests were performed on a drilling system which is used to drill and measure forces and torque during drilling. The effects of drilling speed, feed rate and drill bit diameter on force and torque were discussed separately. The experimental results were proven to be in accordance with the mathematic expressions introduced in this paper.The automatic drilling saved drilling time by 30–60% in the tested range and created less vibration, compared to manual drilling. The deviation between maximum and average force of the automatic drilling was 5 N but 25 N for manual drilling. To conclude, using the automatic method has significant advantages in control drilling force, torque and drilling process in bone drilling.