Selection of drilling conditions for glass fibre reinforced plastics

Abstract

An experimental investigation has been carried out into the drilling of glass fibre reinforced plastics using HSS twist drills. A test series was conducted using a wide range of cutting conditions and drill geometry, namely cutting speed, feed rate, point angle and helix angle. Decisions relating to the ‘optimum’ drilling conditions were based on the geometrical accuracy and appearance of the produced holes. Drill wear was measured during the test trials and used as a further constraint in ‘optimum’ cutting conditions selection. Speed, feed rate and drill point angle were found statistically to be the most significant parameters influencing hole quality. Drill wear can be successfully correlated to the level of the thrust force. A simple nomogram is included to predict drill wear level from the thrust level or the amount of material removed.