Yarn threading and guiding device for false twist texturing machine

A yarn false twist texturing machine having a vertically adjustable device for threading and guiding the advancing yarn at a location between the heater and the cooling plate of the machine. The threading and guiding device comprises a tubular casing having a rodless magnetic piston mounted for sliding movement therein, and a magnetic sliding element and a yarn guide mounted for sliding movement on the outside of the tubular casing. The polarity of the magnetic sliding element is opposite that of the rodless magnetic piston so that the magnetic sliding element follows the movement of the magnetic piston, and the magnetic piston is moved by compressed air delivered into either one or both ends of the tubular casing.