Effects of high pressure supply of coolant in drilling of titanium alloy

Abstract

In order to improve the drilling performance of titanium alloy (Ti–6Al–4V), drilling under high pressure supply of coolant has been investigated. High pressure supply (7 MPa) and conventional supply of coolant are compared mainly on tool wear in drilling by drill with oil holes in its lands. To make clear the causal relation between tool wear and cutting conditions, cutting forces and cutting temperature are measured. The results obtained are as follows; (1) High pressure supply of coolant is effective on drill wear in high cutting speed that drill wear increases significantly under conventional supply. (2) Critical cutting speed is determined from cutting temperature that hardness of tool material decreases remarkably. (3) Under high pressure supply of coolant, cutting temperature does not increase remarkably even in drilling a deep hole because major cutting edges are cooled and chips are ejected smoothly. (4) At low cutting speed and low feed rate, wear of drill is smaller under conventional supply of coolant. (5) It is important to improve the rigidity on drilling system when used at high pressure supply of coolant.