A combine header has a transverse platform carrying a cutting apparatus. An elongated auger having reverse spiral flights move cut material along the platform to a feed housing. The cutting apparatus has a base carrying forwardly projected guards located on 2-inch longitudinal centers. An endless chain carrying knife blades is trained about sprockets located adjacent opposite ends of the base. The knife blades are located on three-inch longitudinal centers. The forward run of the chain moves through a passage in a housing secured to the base behind the guards. The knife blades move over the wear plates attached to the guards to cut material located between the guards. A removable inverted U-shaped insert is located in the passage providing a bearing surface for the front run of the chain and a hold-down lip bearing on the knife blades to hold the blades in close relationship with the wear plates. A hydraulic motor connected to a hydraulic pressure source drives the chain to move the knife blade relative to the guards.