International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1949 Studies on Tool Life and Cutting forces for drilling operation using Uncoated and coated HSS tool Puneeth H V 1 , Smitha B S 2 , 1 Assistant Professor, Department of Mechanical Engineering, New Horizon College of Engineering, Bengaluru, India 2 Assistant Professor, Department of Automobile Engineering, New Horizon College of Engineering, Bengaluru, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Drilling is a machining operation of producing cylindrical hole in solid work piece by means of revolving tool called drill bit. Twist drills are the tools used to carry out drilling operation by rotating the cutting tool that normally has two cutting edges and two flutes with grooves formed in the body. Drill bit coatings make drill bit harder, more lubricated and sharper, heat resistance than uncoated drill bit. Coating the drill bit improves tool life, cutting quality and durability of drill bits. This paper compares the characteristics of HSS drill bit with Titanium Nitride (TiN) and Titanium Aluminium Nitride (TiAlN) coated on HSS for machining of EN8 material under dry machining condition. Parameters such as tool life and cutting forces required during machining of EN8 material for uncoated HSS and Titanium Nitride, Titanium Aluminium Nitride coated HSS drill bit are found out. Experimental results showed that TiAlN coated HSS twist drill had greater tool life compared to TiN coated HSS and uncoated HSS twist drill. Cutting forces such as thrust and torque were found out using drill tool dynamometer. The results showed that the maximum thrust force was developed in TiAlN coated HSS compared to TiN coated HSS and uncoated HSS whereas the torque produced in all the twist drills were at an average values. Key Words: Twist drills; Uncoated HSS drill; TiN and TiAlN Coated HSS drill; EN8 steel, Cutting forces. 1. INTRODUCTION Drilling is a type of machining operation by which cylindrical holes are created in hard work piece, by using a rotating tool called drill bit [6]. During drilling operation a chuck holds the drill bit and rotated at high speed. By using hand roll feed or automatic feed mechanism drill bit is compelled in contrast to strictly clamped solid work piece. The gentle cutting edges of turning drill bit creates a hole by removing excess material in form of chips which gets coiled and escapes across helical grooves provided on drill bit. Even drilling process looks simple, but it is essentially complex one. Comparing with other machining process the tool not only performs cutting act, it also force out chips or cut materials from solid work piece. Drilling can be done on plane or smooth and tilting surface, and on different material like composites, plastics, wood, ceramics and metals. 1.1 Drill Bit and work piece Materials In manufacturing of drill bits wide varity of different materials are used. The different type of material chosen plays an important role in performance and life of drill bit. The commonly used materials are: High speed steel: In present days for manufacturing of drill bits High speed steel is most widely used material. It is an alloyed steel of 14-22% tungsten with molybdenum, vanadium, cobalt and chhromium. HSS drills are classified in to two types namely M-type (10% molybdenum) and T- type(12-18% tungsten). About 95% of M-type series in manufacturing of HSS drills. It has some important characteristics properties like: Harder, Heat resistance, remain sharper during drilling of long time[6[. Titanium nitride(TiN) coated drills: It is an hard ceramic material coated to HSS drills. Coated drill tolls are used to drill metal workpieces, since it has good mechanical properties. Coating HSS drill bit improves self-lubricating and hardness properties. The cutting tool life can be increased by two or more times to the HSS drills. TiN is very hard and inert material, thin film coatings is applied to metal parts. Titanium nitride is a combination of toughness, hardness and inertness. Physical vapor deposition (PVD) system is the environmental safe coating method, for coating thin film on HSS tool [5][7]. Applying TiN coating to metals improves surface chatacteristics. The coated TiN has gold colour with ultra hard material. It has very high chemical resistance which will not corrode during drilling. It has high temperature withstand capacity up to 600 0 c, and non-toxic hence used for food processing equipment and medical surgicals. The coating is up to 3 micrometer thick. It has an wonderfull bond to base material that will not erupt, chip off or flake. TiN coated tools has 3-10 times long life capacity than uncoated tools. Titanium Aluminium nitride (TiAlN): Titanium nitride developes thin film coating of Titanium Aluminium nitride (TiAlN), which offers very high temperature resistance than TiN. It has good hardness property at high temperature, and hence used in high temperature which exceeds limit of TiN. The coating is done by developing thin layer of aluminium oxide ceramic. It is an hard ceramic material coated to HSS drills. Coated drill tolls are used to drill metal workpieces, since it has good mechanical properties. Coating HSS drill bit