Indian Journal of Engineering & Materials Sciences Vol. 24, June 2017, pp.239-246 A novel approach to use internally cooled cutting tools in dry metal cutting Yahya Isik a *, Abdil Kus a , Salih Coşkun a , Kadir Özdemir b & M Cemal Cakir b a Vocational School of Technical Science, Uludag University, TR-16059, Bursa, Turkey b Department of Mechanical Engineering, Uludag University, TR-16059, Bursa, Turkey This paper presents a new cooling method to be used in dry metal cutting. This new cooling method is based on a tool holder with cooling fluid circulating inside a closed internal cooling system. A prototype that facilitates the cooling from inside the tool holder was specifically designed and manufactured. For this study, a series of cutting trials was carried out to investigate the practicality and effectiveness of the internally cooled cutting tool concept. Two techniques, one using a K-type thermocouple and the second using an infrared (IR) pyrometer, were employed to estimate the temperatures of the tool and the tool-chip interface. Experiments were conducted on DIN 1.2379 cold work die steel (50 HRC) using CVD-coated CNMG 190608-IC907 carbide inserts. The experimental results for dry cutting and for the internally cooled tool were compared using fluid dynamic analysis implemented via the ANSYS Fluent FEA code. The internally cooled tool exhibited the advantages of better surface roughness and extended tool life; in addition, machining was enabled at a wider range of cutting speeds while avoiding environmental hazards and health problems. The results clearly indicated that internal cooling could sufficiently reduce the cutting temperature and consequently, by controlling the critical cutting temperature, was able to circumvent it during the turning process. This technique could generally be advantageous for the machining of hard materials. Keywords: Internal cooling, Tool life, Metal cutting, Coolant fluid, Tool holder design The major requirements in machining are higher material removal rate, better surface finish and lower energy consumption. These objectives can be achieved by reducing tool wear with the use of a proper tool cooling system during machining. In the machining process, a considerable amount of energy is transformed into heat through plastic deformation resulting from chip formation, friction between the chip and the tool face and friction between the tool and the work-piece 1,2 . Most of this heat energy is carried away by the chip; the rest is transferred to the tool, to the work-piece and to the environment. The heat transferred to the tool mainly reduces either the mechanical resistance or the wear resistance of the tool 3 . Maximum temperatures arise in the contact zone between the chip and the tool. The temperature distribution depends on the heat conductivity and specific heat capacity of the tool and the work-piece. In the turning operation, friction and heat generation at the cutting zone are frequent problems affecting tool life and surface roughness 4-6 . The heat generation rate, Q (W), is given by Sata and Takeuchi 7,8 as: Q = 1.68af 0.15 V 0.85 , where a is the depth of cut (mm), f is the feed rate (mm/rev), and V is the cutting speed (m/min). In dry cutting operations, friction and adhesion between the chip and the tool tend to be higher, causing higher temperatures, higher wear rates and, consequently, shorter tool lives. At present, completely dry cutting is not recommended for many machining processes due to the necessity of using cutting fluid to prevent the chip from adhering to the tool 9,10 . In the machining process, cutting fluids have been used for many years to reduce the temperature during machining, having the effect of reducing tool temperature, improving tool life and product quality; however, cutting fluid use can result in environmental pollution, health hazards and high production costs 11-13 . Cutting fluids are beneficial in minimizing the length of the chip contact with the cutting tool, reducing the cutting temperature, decreasing the cutting force, improving tool life and work-piece surface conditions, reducing work-piece thermal deformation and flushing away chips from the cutting zone 14-16 . Dhar et al. 17 , investigated the use of cutting fluids has some disadvantages, including added costs involving storage needs, pumping, filtering and recycling, and potential operator health problems caused by gases, fumes and bacteria formed in the cutting fluids. Furthermore, cutting fluids pose a risk of skin cancer after long exposure. The need for green cooling _____________ *Corresponding author (E-mail: yyisik@gmail.com)