Original Article

Performance evaluation of hard turning of AISI 4340 steel with minimal fluid application in the presence of semi-solid lubricants P Sam Paul1 and AS Varadarajan2 Hard turning with minimal fluid application is an emerging machining technique in which cutting fluid is applied in the form of a minimal high velocity narrow pulsed jet so that for all practical purpose it resembles dry and wet turning but at the same time offers better cutting performance. Semi-solid assisted machining is a novel concept to control cutting force, cutting temperature, tool wear and to improve surface finish. In the present investigation, an attempt is made to improve the cutting performance during turning of hardened AISI 4340 steel with minimal fluid through the application of a semi-solid lubricant namely grease in pure form and as a mixture with 10 % graphite applied at the tool–chip interface, tool– work interface and at the back side of the chip using a special semi-solid lubricant applicator developed for this purpose. The results indicated that the use of semi-solid lubricants – grease and graphite at the tool–chip interface along with minimal fluid application reduces tool vibration, cutting force, cutting temperature, tool wear and improves surface finish