The objective of this book is to share the experimental investigations to the readers about the effect of controlled cutting parameters namely cutting speed, feed rate, depth of cut, cutting fluid concentration and two cutting fluids with different base oils on surface roughness (Ra) of EN8 or AISI 1040 steel during turning operation by using design of experiments, custom design method, analysis of variance, leverage plots and desirability profiling using JMP software to study the performance characteristics in wet CNC turning operation. The analysis reveals that feed rate has the most significant effect on surface roughness (Ra) and value of surface roughness does not significantly differ for two different cutting fluids used.