The aim of this study is to find out the effect of TiO2 addition on crystallization behaviour and machinability of glass ceramics having 6:4 weight ratio of potassium mica and cordierite phases. In the first stage of the experimental studies, three glass compositions with potassium mica to cordierite ratio of 6:4 have been prepared, mixed and casted at proper temperatures. One of the compositions didn't contain any TiO2, others contained 1 and 2 mass% TiO2 respectively. 4 mass % CeO2 as a stabilizer and 2 mass % CaO as melting agent were added to glass compositions. In the second stage of the experimental studies, disc and cylindrical shaped glass samples were casted. After heat treatment, microstructure and mechanical properties were determined in terms of micro hardness (HV) and machinability. As a result of experimental studies, it was observed that TiO2 addition promotes cordierite formation. In these glass compositions curved mica that provides machinability precipitated in glass base matrix and cordierite phase that provides hardness and chemical resistance precipitated in boundaries between mica crystals. It was observed that TiO2 addition of 1 mass % and above reduces porosity, thus increasing hardness.