Effect of small quantity lubrication on grindability of hardened AISI 4340 steel

The process of grinding is normally associated with generation of considerable amount of heat. To reduce thermal damages, grinding zone is often flooded with liquid coolant, most of which is wasted and may cause severe environmental pollution. In the present work, grindability of hardened AISI 4340 steel is assessed at various infeeds, using an eco-friendly vegetable oil applied by small quantity lubrication (SQL) technique, so as to reduce the quantity of coolant. At the same infeed, grinding is also performed by applying a uniform layer of semi-solid lubricant (grease) on the work surface. Comparison is made between the two methods in terms of force, surface roughness, specific grinding energy and observed chip forms. Results prove that SQL technique using vegetable oil is better than grease as a lubricant in terms of force requirement, while surface quality shows improvement with grease layer lapped on the work surface than with SQL technique.