“TAGUCHI METHOD BASED OPTIMIZATION OF DRILLING PARAMETERS OF EN31 STEEL WITH PVD COATED AND UN-COATED DRILLS”, JME, vol. 10, no. 2, pp. 112–116, Jun. 2015, Accessed: Jul. 21, 2025. [Online]. Available: https://www.smenec.org/index.php/1/article/view/244