Abstract: A pin-barrel extruder of the type used for processing rubber or thermoplastics materials, for extracting liquids from liquid-solid mixtures and for pulping wood substances includes adjustment means which permit the depth of penetration of the pins, which project into the hollow barrel of an extruder, to be adjusted in a continuous manner. To achieve this, the pins are threadly located in throughbores provided in the barrel so that their radially outer ends project externally of the barrel. On the externally projecting end of each pin, a chain wheel or sprocket is provided which is driven by a chain drive. Actuation of the drive thus alters the depth of penetration of the pins in the barrel.