Abstract: A method of forming a duct liner from a duct insulation board includes cutting a plurality of parallel grooves into duct boards with a plurality of rotary saw blades which are spaced on 1.57 inch or 3.14 inch centers. The saw blades have peripheral teeth which project outwardly on both sides of the saw blades to form grooves in a first major surface of a duct board which are wider than the saw blades. The grooves have sidewalls which extend perpendicular to the first major surface of the duct board and have a depth from 70% to 90% of the thickness of the duct board. The first major surface is typically coated and a second major surface of the duct board normally has a facing adhered thereto. After the duct board is grooved, the duct board can be curved to conform to the curvature of a tubular metal shell, with the parallel grooves of the duct board extending parallel to the axis of curvature, and placed in the tubular metal shell as a liner to form an insulated air duct.

Abstract: A duct insulation board grooving apparatus cuts a plurality of parallel grooves into duct boards with a plurality of rotary saw blades which are spaced on 1.57 inch or 3.14 inch centers. The saw blades have peripheral teeth which project outwardly on both sides of the saw blades to form grooves in a first major surface of a duct board which are wider than the saw blades. The grooves have sidewalls which extend perpendicular to the first major surface of the duct board and have a depth from 70% to 90% of the thickness of the duct board. The first major surface is typically coated and a second major surface of the duct board normally has a facing adhered thereto. After the duct board is grooved, the duct board can be curved to conform to the curvature of a tubular metal shell, with the parallel grooves of the duct board extending parallel to the axis of curvature, and placed in the tubular metal shell as a liner to form an insulated air duct.