Abstract: A plurality of intermittent incisions are made in the surface region of a fiberboard to sever fibers without removing them from said region. The resultant fiberboard may be molded under heat and pressure to a three dimensional hardboard with high fidelity to the mold and without causing stretch marks, tears or fractures. The fiberboard may be a dry consolidated mass of wet felted cellulosic fibers. The invention is particularly valuable in the molding of boards made from redwood fibers and other long fibers.The intermittent incisions may be made along one or more lines parallel to or perpendicular to the longitudinal edge of the fiberboard but a grid of incisions along intersecting lines is advantageous. To cut the incisions, the fiberboard is moved on a conveyor belt while an assemblage of toothed cutting disks is rotated in cutting engagement with the board. The cutting disks are mounted co-axially on a motor-driven shaft.

Abstract: A fiberboard, preferably made by consolidating a water-felted mat without added binder and being suitable for pressure-molding into a hardboard door facing having a high degree of fidelity to the contours of the die set, is incised on both the major face and the obverse face with incisions having a depth of from about 10% to about one third the thickness of the board. The incisions are aligned on lines that are preferably arranged at right angles across the face of the board. The lines are preferably spaced a maximum of about 0.5 inches apart, and the incisions on each line are discontinuous, preferably separated by a maximum of about 0.5 inches.