Statistical Analysis of the Effects of Feed, Speed, and Wear on Hole Quality in Drilling

A statistical analysis of hole quality in drilling was performed. Using standard twist drills, holes were drilled dry in hot rolled steel. The effects of feed and speed on the hole quality features of oversize, out-of-roundness, location error, angularity error, and taper were examined using a full factorial analysis of variance. The effects of workpiece surface condition, geometrical variation among drills, and drill wear were qualitatively observed. The results showed that feed and speed have a relatively small effect on the measured hole quality features. With the exception of hole location error, the hole quality was not predictably or significantly affected by the cutting conditions. Although these results were not expected, they have the important positive implication that production rates may be increased without sacrificing hole quality. The drilling feeds and speeds would be constrained by factors other than hole quality, such as drill wear, drill breakage, or force, torque, and power limits.