Mechanical lockings of floor panels and a tongue blank

A set of floor panels provided with a locking system comprising a displaceable tongue in a displacement groove in a first edge of a first floor panel, wherein the displaceable tongue is configured to cooperate with a tongue groove at a second edge of a second floor panel for vertical locking of the first and the second edge,

• the locking system further comprises a locking strip with a locking element which is configured to cooperate with a locking groove for horizontal locking of the first and the second edge, the displaceable tongue comprises a protrusion and the displacement groove comprises a cavity, the protrusion is configured to be cooperate with a wall of the cavity such that the displaceable tongue is displaced in a first direction, perpendicular to the first edge and the second edge, when the displaceable tongue is displaced in a second direction along the edge, wherein the displaceable tongue is displaced from the displacement groove and partly into the tongue groove,
• wherein the protrusion is flexible and is configured to exert a horizontal pretension against the tongue groove.