Insulation board feeding apparatus feeds successive boards from a pallet stack to a grooving machine to make pre-formed duct sections. The apparatus includes a cable driven elevator assembly, a reciprocating transfer carriage with a plurality of pivotable board-engaging fingers which is reciprocated by an air cylinder, and a guide assembly comprised of two non-driven rollers. The machine of the present invention is simpler, more reliable and less expensive to manufacture than its predecessors.