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The high demand of miniaturized components, coupled with geometric and material range limitations of traditional lithographic techniques has generated a strong interest in micromechanical machining. In micromachining the so-called size effect is a dominant factor. This is attributed to the fact that the unit or physical size of the material to be removed can be of the same order of magnitude as the tool edge radius or grain size. This paper explores the micro-machinability of multi-phase ferrite—pearlite steel that has a relatively large average grain size (10 μm). The investigation and cutting tests examined the effect of undeformed chip thickness, tool edge radius, and workpiece grain size on the specific cutting force, burr size, surface finish, and tool wear. The work clearly shows that micro tool edge radius and workpiece material grain size are valuable inputs in determining micromilling conditions that ensure the best surface finish and reduced burr size. Cutting conditions recommendations are also put forwards for roughing and finishing passes in micromilling of AISI 1045 tool steel.

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In micro-machining, determination of the minimum chip thickness is of paramount importance, as features having dimensions below this threshold cannot be produced by the process. This study proposes a methodology to determine the value of minimum chip thickness by analysing acoustic emission (AE) signals generated in orthogonal machining experiments conducted in micro-milling. Cutting trials were performed on workpiece materials ranging from non-ferrous (copper and aluminium), ferrous (single- and multiphase steel) to difficult-to-cut (titanium and nickel) alloys. The characteristics of AErms signals and chip morphology were studied for conditions when the tool was rubbing the workpiece. This provided a foundation to contrast AE signals captured at higher feed rates. This study enabled the identification of threshold conditions for the occurrence of minimum chip thickness. The values of minimum chip thickness predicted by this new approach compare reasonably well with the published literature.