A portable bag-closing sewing machine is provided with a self-oiling system which includes an oil reservoir connected to the machine and oil-delivery means to direct oil from the reservoir into the inner chambers of the machine where oil is distributed by gravity flow, capillary action and movement of machine components, the oil moving along through the machine components and through a series of channels, troughs, and reservoirs within the housing to distribute oil throughout the machine. During operation, the rotating and reciprocating machine parts fling oil outwardly within the chambers to directly oil machine assemblies and to create a fine mist of oil throughout the chambers so as to further lubricate machine components. Also disclosed is an improved and self-lubricating feed dog assembly and thread chain cutting device.