A dipper assembly includes a dipper, a dipper door, a closure mechanism, a trip assembly, and a camshaft support assembly. The dipper door is pivotally mounted to the dipper for movement between an open position and a closed position in which the dipper door covers the dipper bottom. The closure mechanism is configured to retain the dipper door in the closed position. The trip assembly is configured to release the dipper door for movement to the open position, and includes a trip arm coupled to a camshaft and also coupled to a trip rope. The camshaft support assembly is configured to receive the camshaft, and includes a bearing block receiving a rotatable bearing member, and a sealing mechanism.