This article presents comparisons of cutting performance of Austrian made – Si3N4 nitride ceramic – inserts used in machining a Type 422425 grey cast iron work-piece materials. Three commercial ceramic inserts Type FMG121C, FMG122C, and FMG134C were tested. Experiments were focused on tool life tests. A comparison approach involved exponents of Taylor’s type equations over an optimized cutting tool interval i.e. one constant depth of cut of 1mm, one constant feed rate of 0.2 mm/rev and the three cutting speeds 250, 320 and 380 m/min. Results were obtained from linear regression. Also conducted was an evaluation of intervals of reliability as well as corresponding standard deviations for each regression coefficient in experimental Taylor’s equations. The experiments allowed to compare, from statistical perspectives, at a 95 and greater confidence level, the trends and quantities of experimental cutting inserts. The results showed that a Type FMG122C ceramic insert had the most superior performance compared to other two types of experimental ceramic inserts investigated in this study.