Knife holder of a tube cutting unit for tube manufacturing and a system and use of the system for tube manufacturing

A knife holder (402) for a tube cutting unit (400), which tube cutting unit (400) is adapted to receiving a rotating tube (2) fed outs from a tube manufacturing device (1) in a feed direction (316) which for one length unit is parallel with the longitudinal direction of the tube (2), such that rotation takes place about an axis (310) in the longitudinal direction of the tube (2), wherein the knife holder (402) is configured to be movable via bearing elements (414) on the knife 10 holder (402) which communicates with fastening elements (416) disposed on the tube cutting unit (400), the knife holder (402) comprises first and second shaft-bearing parts (410, 412) and there is between the shaft-bearing parts a shaft (408) which supports a centred knife element (404) with cutting edge (406), wherein a back-up (418) is situated opposite to the knife element (404) in such a way that the back-up (418) is within the periphery of the tube (2) being made and cooperates with the knife element (404) during the cutting operation.