Lead press guides made from polyphenylene sulphide composite (PPS GF 40) and used to keep microelectronic devices accurately in their respective testing equipment are machined from sheet form on the CNC machine. Precise manufacturing of lead press guides within strict dimensional tolerances is difficult considering anisotropy of the material and different thermal responses during machining. The main objective of this work was to optimize the machining process and stress relief (annealing) protocol to obtain high quality parts with minimal distortion and low stress levels. Residual stresses in the sheet were relieved during annealing treatment. Only initial machining of the lead press guides was imposed, since the roughing generates more heat and internal stresses than the finishing operation. The main milling parameters that were considered were the depth of the cut, the feed rate and spindle speed. The general principles of experimental design were followed and guidelines of optimal machining conditions obtained. To obtain the minimum distortion of the top edge and lower thinner edge of the guides two cuts of 5.5 mm were used to remove most of the material. The spindle speed was kept at a constant programmed value, while feed rates should be between 115 and 135% to reach a compromise between distortion of both the top and bottom edges of the guides. The dimensional stability of lead press guides in the temperature range of -50 to 125degreesC was analyzed although in practice the thermal properties of PPS GF 40 do not allow its use over such a wide temperature range.