Abstract: The replaceable insert for a hammermill hammer enables the insert to be removed and replaced by the removal and installation of a single bolt in the leading face or edge of the hammer, rather than requiring partial disassembly of the hammermill for the removal of a damaged hammer and hammer shank from its retaining rod. The insert is formed of hard and tough metal, e.g., tool steel, carbide alloy, etc., as a longitudinally and laterally symmetrical rectangular parallelepiped, the hammer shank having a cooperating relief formed therein. The symmetrical configuration allows the insert to be reversed through 180° in its installation, thereby exposing a fresh insert face after the first face has been worn or damaged. A pair of indexing pins extends from the insert, the pins fitting closely within cooperating receptacles in the hammer shank relief to secure the insert precisely within the relief.