As mentioned before, drilling 2000 holes is the normal industrial
standard for reuse of drills. Hence, the wear observed after
drilling 2000 holes under the reference conditions was used as the
wear standard, and the tool life under other conditions was estimated
from the wear trend. Fig. 8 shows the estimated tool life
values in terms of the process parameters, together with a fitted
plane using the modified Taylor tool life equation (4). Since the
Taylor model employs the spindle speed instead of the chip load,
the surface was plotted with respect to the in-feed e rotational
speed plane; the estimated values fit the traditional Taylor equation
well