Revised recommendations of the international working group for diagnosis

Screw for a plate-type extruder. The screw comprises at least one screwthread which starts, at the root of the screwthread, in the form of an arcuate spade portion and has in a portion of the screwthread adjacent the spade portion a cross-sectional shape having a concave crest. The root of the screwthread has a conventional cross-sectional shape having a crest parallel to the axis of the screw.