DRILLING OF BONE

Experimental results [on human bone] were presented which show the interrelationships among thrust pressure, feed rate, torque and specific cutting energy for 3 types of drill bits. The 3 types of drill bits used included a common surgical twist bit, general purpose twist bits of various diameters of the type normally used for drilling into metals and a specially constructed spade bit. Performance of all 3 types of drill bits can be characterized by power function relationships of the same form. Clogging of drill flutes was identified as a serious problem which caused increased torque and energy as the drill bit penetrated deeper into the bone. Optical and scanning EM of drilling chips indicated that chip formation occurred primarily by a fracture process with localized deformation resulting from the action of the chisel edge at the tip of the drill bit.