This thesis presents six optimization models which are developed and solved in two stages in order to integrate tolerancing and machining parameters decisions. One model is developed in the first stage. The first-stage model is related to a design problem and provides better part tolerance to be used in the second stage to incorporate tool adjustment decisions into the optimization of machining parameters. Five models are developed in the second stage and are divided into single-machine and multi-machine turning operation problems. For single-machine turning operations, three models are formulated. The first is a single-product multi-pass model considering pass selection for determining optimum cutting speed, feed rate, depth of cut, dimension deviation and number of passes. The second is a single-product multi-pass model considering inventory and setup costs to find optimum cutting speed, feed rate, depth of cut, dimension deviation and batch size. The third is a multi-product multi-pass model considering inventory and setup costs for selection of optimum cutting speed, feed rate, depth of cut, dimension deviations and production cycle time. For multi-machine turning operations, two models are formulated. One is a multi-feature multi-pass model with the objective of minimizing total cost for determining optimum workload assignment, cutting speed, feed rate, depth of cut, and feature dimension deviations of machine-pass-feature combinations. The second is a multi-feature multi-pass model with the objective of minimizing cycle time which, once solved, will give optimum workload assignment, cutting speed, feed rate, depth of cut, and feature dimension deviations of machine-pass-feature combinations. A solution method and illustrative examples are given to test the feasibility of the developed optimization models.