Abstract: Various metal cations, including Na +, K +, Ca 2+ , and Ba 2+ , were introduced into water based load carrying additives by molecular modification. The machining efficiencies of the water based cutting fluid containing these additives were evaluated in tapping torque test of Ti 6Al 4V alloy. The morphology of the machined Ti alloy surface was examined with a scanning electron microscope. The chemical states of various elements on the machined Ti alloy surface were investigated by means of X ray photoelectron spectroscopy. It has been found that Ba containing additive shower the best tapping efficiency and surface quality.