Abstract: A thread, suitable for use as a sewing thread, and having increased tenacity and reduced thermal shrinkage properties. A multi-filament core yarn for the thread is formed from a preoriented yarn having a titre of 100 dtex-1,000 dtex which has been turned around an unheated pin of less than 10 mm diameter, heated to a temperature of 100.degree.-200.degree. C. for 0.01-10 seconds, and drawn with a drawing ratio equal to or greater than a normal drawing ratio. At least one effect yarn is intermingled with the core yarn to form a core-jacket thread having loops, not more than 15% of which are drawn tight in a knot-like manner.

Abstract: In a method and apparatus for producing a yarn, a synthetic pre-oriented multifilament yarn is fed at a first velocity to a non-heated pin having a diameter less than 10 mm. After turning the yarn around the pin for an angle between 270.degree. and 360.degree., the yarn is heated to a temperature between 100.degree. C. and 250.degree. C. for between 0.01 sec and 10 sec. The yarn is then drawn off the pin at a second viscosity higher than the first velocity.