Helical screw conveyor unit, worm shaft, worm extruder, and method for providing a worm shaft

A helical screw conveyor unit configured as an exchangeable element for a helicoidally or spirally winding helix of a worm shaft, having a main body extending along a longitudinal axis, the main body having two axial end regions and a lateral surface that connects the end regions to one another, at least one helicoidally winding helix element being arranged on a top side of the lateral surface and extending radially outward away from the top side,

• wherein
• the top side of the lateral surface is concavely curved in shell-like form about the longitudinal axis, and the main body has a radial opening, the radial opening being configured such that a fastening region of a shank of the worm shaft can be led through the opening in a direction perpendicular to the longitudinal axis and can be arranged in a cavity formed by the main body,
• the helix element has at most one half of one helix turn,
• the lateral surface of the main body has an inner surface configured for being seated on the fastening region, and
• the helical screw conveyor unit has at least one fastening element configured for detachably fastening the main body to the fastening region.