Two face turning tests are performed to determine tool life equation constants Stainless tube of internal and external diameters of D1=40 mm and D2=60mm, respectively is used. The first test was performed over 8 facing passes using spindle speeds of N1=300 rpm, and the second tests was performed over 12 passes using spindle speed of N1=250 rpm. The testes were performed using feed rate of 0.15 mm/rev. The total machining time of the first and second tests are 2 min and 4 min, respectively. If the flank wear after 8 facing passes of the first test is 0.18 mm, while the flank wear after 12 facing passes of the second test is 0.16 mm. Assuming a certain tool wear criterion (i. e. VB =0.3 mm), determine the tool life constants.