The dosator (1) of the machine comprises a linearly movable dosing top plate (22) disposed underneath the open bottom of a powder tub (9) in sliding contact with the open bottom of the powder tub and a linearly movable bottom support plate (27). The leading edge (23) of the top plate extends over the leading edge (24) of the bottom support plate in the direction of one side of the powder tub having a piston assembly (10) externally of the powder tub. The leading edge of the top plate has a row of dosage metering passages (30) extending transversely therethrough and exposed at the open bottom of the powder tub and opening onto the bottom support plate. A differential drive means (31a) operates to move the top plate and bottom support plate together in the direction of the said one side of the powder tub with dosages of powder in the dosage metering passages in the top plate and then to move the bottom support plate in the reverse direction followed by the top plate. The dosator forms uniform dosages of powder and has several other advantages. (Fig 1).
