A storage cabinet (1) that may be used to store CAD/CAM milling blanks (45) such as those used in dentistry. Drawers or box assemblies (3) are placed on shelves (4) within the cabinet (1). Each box assembly (3) includes a forward compartment (15) which includes a lower cavity (16). Perforations (17) in the top surface (20) of the forward compartment permit a spindle retaining assembly (23) within the cavity (16) to grip the spindle or shaft (46) of a blank which may be readily viewed and removed by a user as needed. The retaining assembly (23) includes an orthogonal groove (32) that is biased by a spring (29) in order to permit spindles of various sizes and geometries to be retained.