Abstract: A mini-sized hammer mill apparatus is adaptable for both rotatable tub feeding of hay, fodder, feed grains, and the like, as well as for chute feeding of wood and debris for comminution. A number of features optimize the mini size for effective, reliable, and smooth operation by small horsepower tractors, including: side feed tangentially out of a cylindrical hopper under a rotatable tub into the periphery of a large diameter, narrow rotor, or through a chute with tensioned roller feeder; radially adjustable grinding and metering finger/grate bar combination, secondary grinding fingers and breaker bar, self-sharpening hook-like pointed hammers, rotatable tub mounting structure, and enhanced energy dissipating, down-sized cyclone with reverse-louvered pressure dissipators.