A coffee grinder assembly for a coffee machine comprises two coaxially arranged grinding wheels. One of the grinding wheels is driven by an electric motor, and the other one is stationary. For receiving the grinding wheels, two grinding wheel support members are provided. Each grinding wheel is provided with radially extending protrusions, and each grinding wheel support member is provided with corresponding recesses to form a bayonet closure. By such a design, the provision of connecting bores in the grinding wheels can be avoided, resulting in an enlarged effective grinding surface.