Abstract: A wood chip sizing apparatus, based on the thickness dimension, which includes a gyratory screen system (16) comprising three separate screens (18, 22, 26) which produces a total of four fractions, one fraction (20) comprising substantially all overthick chips, another fraction (24) comprising both overthick chips and accepts, another fraction (28) comprising substantially all accepts, and another fraction (30) comprising substantially all unders. Fraction (20) is moved directly to a chip slicer (52) which reduces the size of substantially all the chips to accepts. Fraction (24) is directed to a second screening station (42) which separates fraction (24) into two further fractions (44 and 46), one of which (44) comprises overthick chips, and the other of which (46) comprises accepts. The overthick chips (fraction 44) are applied to the chip slicer (52).