Investigation of Machinability in Milling of Difficult-to-Cut Materials Using Water Soluble and Water Insoluble Cutting Oil

Abstract

The machinability of difficult-to-cut materials was evaluated during the milling process using water soluble and water insoluble cutting oils. The fundamental characteristics of the cutting oils were investigated by the pin-on-disk abrasion test. The machinability was evaluated by the tool flank wear, chip geometry, cutting force, and tool-flank temperature during milling. The tool-flank temperature was measured using a two-color pyrometer with an optical fiber. Workpiece materials consisting of stainless steel and a titanium alloy were used along with commercial cutting oils. From the results of the pin-on-disk abrasion test, the friction coefficients resulting from the application of various cutting oils to the face of the titanium alloy and WC-based hard metal were approximately the same value. The water soluble cutting oil had a higher coolability than the water insoluble cutting oil. From the results of the milling test, the water insoluble oil had a higher machinability of the difficult-to-cut materials than the water soluble cutting oil. The tool-flank temperature during wet cutting of the difficult-to-cut materials decreased by approximately 50–80 °C compared to dry cutting. However, no differences in the tool-flank temperature were observed between the water soluble and water insoluble cutting oils. The cutting force during wet cutting increased compared to dry cutting, most likely because the heating during cutting was reduced by supplying the cutting oil, and the material at the cutting point did not cause heat softening.