A Genetic Tool Monitor (GTM2) was developed to evaluate tool condition by estimating the key parameters from cutting forces. Genetic algorithm of the GTM2 is capable of estimating a large number of parameters with desired resolution. Theoretically, the method should work with the resultant force or any force component data with the same accuracy. This concept was tested on the simulated cutting force data. Simulations showed that any force component could be used to estimate the critical parameters with the same accuracy of the resultant cutting force. Use of the resultant force is recommended in the experimental studies to avoid significant estimation errors and false alerts caused by the noise and modeling errors.