In this paper, the optimal intervene hazard and their associated optimal tool replacement times were found considering three models of optimization, namely cost optimization, availability optimization, and cost-availability optimization. The cost-availability optimization was done by taking into consideration replacement costs, replacement times and costs of downtimes. Experimental data was collected during turning titanium metal matrix composites (TiMMCs). In the surface finishing process, cutting tool is used under low constant cutting speed, small constant depth of cut, and changeable feed rate. The Proportional Hazards Model (PHM) is used to model the tool’s reliability and hazard functions using EXAKT software. The experimental results are used to construct, and then validate, the PHM model.