Abstract: A wood chipper embodying a pair of adjacent discs mounted in face-to-fact relation on a drive shaft for rotation therewith. The discs are secured to each other and have angularly spaced aligned passageways therethrough. A recess is provided in one disc at the trailing side of each angularly spaced passageway, as viewed in the direction of rotation. A knife holder mounted within each recess carries a knife which is retained by a knife clamp. Interlocking means between the clamp and the knife holder limits relative movement therebetween both axially and radially to maintain accurate location of the knives. The end of the knife holder removed from the aligned passageways is spaced from its disc to define a cavity which receives babbit. Also, the edge of the knife opposite its cutting edge is spaced from the knife holder and may have slots which extend at an angle relative to the cutting edge to define cavities which receive babbit.