Shielded needle unit with rotating needle

A needle unit comprising:

• a needle hub,
• a hollow needle mounted in the needle hub and having a pointed distal end protruding from the needle hub, the hollow needle defining a reference axis,
• a shield in which the needle hub is fully or partly arranged, the shield being axially moveable relative to the needle hub between an extended position in which the shield axially covers the needle distal end, and a retracted position in which the needle distal end protrudes from the shield corresponding to a needle free length,
• a coupling allowing the needle unit to be used in combination with a drug delivery device, and
• a linear-to-rotational movement converter mechanism causing the needle hub to be rotated relative to the shield when the shield is moved from its retracted to its extended position,
• wherein the linear-to-rotational movement converter mechanism has an initial axial slack,
• whereby rotational movement of the needle hub relative to the shield takes place after at least 25% of the needle free length has been covered by the shield.