Abstract: A screw conveyor with a slowly rotating feed screw for precision metering by conveying very small amounts of loose material between screw threads, the same amount of loose material being discharged from the end of the conveyor with each turn of the screw. During the relatively short time interval of a single revolution, which can last one minute or even a multiple thereof as needed, the conveyor capacity itself fluctuates, since discrete amounts of the material being conveyed are always delimited by the individual threads of the feed screw. In order for a screw conveyor to be usable for precision metering of very small amounts to be conveyed; i.e. for conveying very small amounts with a high degree of constancy without the periodicity caused by the nature of the feed screw, the screw conveyor is provided with a rotatably mounted tube surrounding the discharge end of the fixed feed tube and which is driven at a rotational speed proportional to the rotational speed of screw.