For micromilling to be used in the manufacturing of glass-based devices, further machining research is required to find optimum cutting configurations to produce high quality micro-scale features. It is not only extremely expensive but also difficult to investigate machining mechanism by means of various experiments. In this paper, the effect of cutting condition on cutting mechanics is numerically studied in glass micromilling with a micro-ball end mill. Mechanistic stress model is developed when straight grooves are machined to investigate cutting regime transition. By considering variation of tool tilt angle, cutting depth, and feed rate to investigate the cutting force and pressure stress within the contact area are computed. The predicted cutting force and pressure stress information can provide insight into how and when ductile machining happens in when glass is cutting.