International Journal of Machine Tools & Manufacture 42 (2002) 733–740 An investigation on surface grinding using graphite as lubricant S. Shaji, V. Radhakrishnan * Manufacturing Engineering Section, Department of Mechanical Engineering, Indian Institute of Technology, Chennai 600 036, India Received 31 July 2001; received in revised form 2 November 2001; accepted 9 November 2001 Abstract Grinding requires high specific energy and the consequent development of high temperature impairs workpiece quality by inducing tensile residual stress, burn, micro cracks etc. Control of grinding temperature is achieved by providing effective cooling and lubrication. Conventional flood cooling is often ineffective due to the relative inaccessibility of the fluid to the actual grinding zone, film boiling etc. Further these fluids are also a source of health hazards. Minimization and possibly the elimination of fluid coolants by substituting their functions by some other means is of current research interest. This paper deals with an investigation on using graphite as a lubricating medium to reduce the heat generated at the grinding zone. An experimental set-up has been developed for this and a detailed comparison has been done with dry and coolant flooded grinding in terms of forces, specific energy, tempera- ture and surface finish. Results show that grinding force, energy and temperature are reduced and resultant surface finish depends on workpiece material.  2002 Elsevier Science Ltd. All rights reserved. Keywords: Grinding; Lubrication; Coolant; Graphite 1. Introduction Grinding is distinguished from other conventional machining operations on many aspects, such as the tool geometry, large contact area and high friction between tool and workpiece and high specific energy require- ment. Specific energy in grinding is one order higher than that in other conventional machining processes like turning and milling [1]. This high specific energy vir- tually ends up as heat and a major portion of it is trans- ferred to the work piece [2–4]. This intense heat input impairs the work piece quality by inducing thermal dam- ages in the form of burning, surface and subsurface cracks, phase transformations, tensile residual stress, dimensional distortions etc. [5–7]. So effective control of the heat generated at the cutting zone is essential to ensure the work piece quality in grinding. Fluid coolants have been the conventional choice to deal with this problem. Detailed research has been reported on the coolant type, its composition and supply characteristics [8]. However, due to the typical nature of * Corresponding author. Tel.: +91-44-445-8518; fax: +91-44-445- 8578. E-mail address: vprmfg@hotmail.com (V. Radhakrishnan). 0890-6955/02/$ - see front matter  2002 Elsevier Science Ltd. All rights reserved. PII:S0890-6955(01)00158-4 the grinding operation, coolants are relatively inaccess- ible to the grinding arc. So, often it is ineffective in reducing the grinding zone temperature, but only pro- vides bulk cooling of the work piece. The stiff boundary layer forming around the rotating grinding wheel also inhibits the access of the fluid to the grinding zone [19,21]. The effectiveness of grinding fluid is also restricted by the fact that they lose their cooling proper- ties upon film boiling and that the film boiling tempera- ture of conventional coolants are lower [9]. However, flooded coolant operation allows effective removal of grinding swarf, which is needed in grinding. Conventional grinding fluids are a source of environ- mental hazards and increasingly strict regulations are coming up with regard to their use and disposal [10]. The cost of these fluids is also high [15,16]. These factors prompted investigations on the use of biodegradable coolants, minimum quantity coolant and coolant free grinding [11]. But any attempt to minimize or avoid the coolant can be dealt with only by the substitution of the functions normally met by the coolants by some other means. Grinding employing cryogenic cooling by liquid nitrogen and Minimum Quantity Lubrication (MQL) by ester oil supplied in the form of spot jet or spray mist are the alternative approaches towards this end [12–18]. The objective of the present investigation was to