Abstract: Cylindrical bobbin cores have at least one radially oriented slot formed in at least one end thereof. The slot is sized and configured to mate with a radially extending blade associated with the drive head of the winder so as to achieve positive rotational drive therebetween. In view of this interconnection between the core and the drive head, significantly less spring pressure needs to be exerted against the core by the tail stock of the winder.

Abstract: Magnetized bobbin cores are preferably wound with sewing thread to obtain sideless, pre-wound bobbins that have beneficial draw-off tensions, draw-off tension uniformity and overspin characteristics. The pre-wound sideless bobbins may thus be satisfactorily used in lock stitch sewing applications due to improved uniformity of draw-off tension combined with reduced bobbin overspin. The magnetized pre-wound sideless bobbins are also especially well suited for end-use sewing applications where automatic bobbin changing equipment is employed. Most preferably, the core is a cylinder formed of a thermoplastic or thermoset material in which magnetized particles are dispersed.