This paper presents analytical and experimental results of ductile-mode machining of brittle material by milling process. In milling process of brittle material, feed per edge is the predominant parameter to achieve ductile-mode machining and hence it limits the permissible material removal rate. An analytical model has been proposed to evaluate the effect of tool diameter on the critical feed per edge for ductile-brittle transition in milling process of brittle material. The proposed model has been validated experimentally by performing microcutting tests on tungsten carbide workpiece by milling process. It has been established by the model and the experimental results that an end-mill of larger diameter improves the critical feed per edge for ductile-brittle transition in milling process of brittle material.