Screw having a web formed undercut for an extruder or conveyor

A screw for an extruder or conveyor conveying screw or dosing screw for polymers, having a web running helically around a core or screw base, wherein the web at least in a section of the screw is formed with an undercut on its active conveying flank in a conveying direction, wherein the screw, at least in a section of the screw, has an intake depth, measured between an envelope of the screw and the core in a region between two adjacent webs, wherein for the intake depth t1 applies:

• 0.03*d≤t1≤0.35*d, wherein d is the outer screw diameter in this region,
• wherein
• the core, at least in a section of the screw, in a region in which the active conveying flank merges into the core or screw base, has an additional recess in which the core diameter is smaller than in the adjacent regions, wherein for additional depth t2 of the recess applies:
• 0*t1≤t2≤t1,
• and in that a core section of the screw is formed adjacent to the recess, straight in a normal cutting plane, which is inclined at an angle in the range of 0°≤w4≤45° to the envelope of the screw.