Effect of pilot hole on thrust force by saw drill

The applications of composite materials are numerous, especially in the structural parts of aerospace, automotive and marine industries. Owing to the marked anisotropy and macroscopic heterogeneity of composite materials, the mechanics of machining used is different when compared to metals. Delamination is one of the most concerns of applying the fiber-reinforced composite materials in various industries. A hole is pre-drilled to eliminate the thrust caused by the chisel edge of twist drill; thus, the threat for delamination is significantly reduced. Saw drills eliminate the chisel and utilize the peripheral distribution of the thrust in drilling. An analytical approach to identifying the role of the pilot hole was proposed to reduce the thrust force-induced delamination during saw drilling. The predicted critical thrust force is in good agreement with the experimental values. (C) 2007 Elsevier Ltd. All rights reserved.