A replaceable mower blade assembly for attaching to a rotatable spindle, motor, or engine crankshaft is provided. The blade assembly includes a mounting member having a plurality of ends extending from a central bore that is configured to receive the spindle, motor, or engine crankshaft. Each end includes an indexing aperture and a plurality of caps. A locking mechanism is operatively connected to the mounting member, and each arm of the locking mechanism includes a pin. A cutting blade is removably attachable to each end of the mounting member and the cutting blade includes an indexing aperture and a plurality of keyhole apertures. Each pin of the locking mechanism is insertable and engageable with an indexing aperture of both the mounting member and the cutting blade for positively securing each cutting blade.