Influence of cutting condition on chip morphology when turning hardened stainless steel using coated carbide cutting tools under minimum quantity of lubrication

The quality of the machined surface is considered as one of the most important characteristics in machining due to the relation between customers' requirements and high performance demands. Machining process, including the resulting surface finish, is significantly influenced by chips generated. Minimum quantity of lubrication (MQL), which sprays small amount of cutting fluid to the cutting zone area with the aid of compressed air, is an ecofriendly cutting fluid application technique with similar advantage to conventional flood cooling. This paper investigates the effect of cutting speed (100 – 170 m/min) and feed rate (0.16 – 0.24 mm/rev)) on chip morphology when turning a hardened AISI 420 stainless steel under MQL using castor oil. Chip forms, thickness, and hardness were observed. It was found that continuous chip was generated at low cutting speed at all feed rates and saw toothed or segmented chips are produced at medium and high cutting speeds and feed rates. Cutting speed and feed rate influenced the thickness of the chip generated.