In this work a factorial planning had been used to evaluate the CBN tool life during cut-ting SAE 8620 steel. Part U2222 of a TPGW 160408 insert of TX-LS TB650 and 2NU-SHMA6942 S7182BN300 classes from two manufacturers were used in this experiment. A 23 factorial design was used In cutting process to evaluate the behavior of the tool life and reason of the exchange of the part on influences of the chamfer (in S and T+S), the advancing speeds (0.09, 0.10 and 0.11 mm/rpm) at a cutting speed of 91.2 m/min. Model have been fit by variance analysis (ANOVA) and the processing optimization was done by response surface methodology (RSM). Results showed that a hyperbolic model had more adjusting than other models and the optimization showed a high life time for the TX-LS TB650 tool from A manufacturer on 0.09 mm/rpm of advancing speed, where it was observed that the pre-cranking was the reason of the exchange.