Abstract: Drop pin for stop motion (1) comprising a body (2) with a yarn lead-through opening (3) provided to rest on a thread extending through this opening (3). The drop pin is supported by a supporting surface or edge (4), forming a concavely curved bordering of this opening (3) and which, in cross-section, has a convex form. The supporting surface (4) may have a rounded spherical form or a form with a number of angle forming sides, such as for instance a polygon. Preferably, the yarn lead-through opening (3) is circular. Also provided is a device for detecting the thread breakage on a weaving machine, comprising a number of similar drop pins for stop motion and a weaving machine provided with a similar device.