Analytical Model of Progression of Flank Wear Land Width in Drilling

In multi-point operations like drilling, cutting velocities and cutting edge geometries vary along cutting lips so is the rate of progression of flank wear. Analytical evaluation of flank wear land width in the case of complex tools has received a limited attention so far. This work evaluates progression of flank wear in orthogonal machining and adopts it to drilling. An abrasive flank wear has been modeled, wherein, cutting speed determines the rate of abrasion, and the feed rate determines the chip load. The model considers stress distribution along rake surfaces, and temperature dependent properties of tool and work materials. Assuming that the flank wear follows a typical wear progression as in a pin-on-disc test, the model evaluates cutting forces and the consequent abrasive wear rate for an orthogonal cutting. To adopt it to drilling, variation in cutting velocity and, dynamic variation in rake, shear and friction angles along the length of the cutting lips have been considered. Knowing the wear rate, the length of the worn out flank (V_B) has been evaluated. The model captures progression of flank wear in zones I, II and III of a typical tool life plot. It marginally underestimates the wear in the rapid wear region and marginally overestimates it in the steady-state region.