Monocortical pin (1) for an external fixator for temporary and/or permanent fixing applications for treating bone fractures and connecting two or more bone fragments together, comprising an elongated cylindrical stem (2) which extends along a longitudinal axis (X) and a conical portion (3) with a tip having an external thread for inserting the pin (1) inside a bone; where said elongated cylindrical stem (2) has a flattened surface (2a) which lies along a reference plane (A) parallel to the longitudinal axis (X) and said conical portion (3) with the tip has an overall length, measured along the longitudinal axis, equal to the diameter (d) of the stem (2) +20% of said diameter (d); said monocortical pin (1) is characterized in that the conical portion (3) comprises a tip (31) which has a centring zone (33) which extends longitudinally over a length equal to 6-8% of the diameter (d) of the stem (2), and a threaded portion (32); moreover the conical portion (3) comprises two base cones (3a and 3b) having two different angles of conicity, a first base cone (3a) in a distal position with respect to the elongated cylindrical stem (2) of the monocortical pin and a second base cone (3b) in a proximal position with respect to the elongated cylindrical stem (2) of the monocortical pin; said first base cone (3a) having an angle of conicity of 13°; said second base cone (3b) having an angle of conicity of 26°.