Chock for mounting a roll in a roll housing of a roll stand, with a main bore for receiving a pin of the roll; a feed for lubricant; a return for the lubricant; a pump device for conveying the lubricant returning from the chock via the drain; wherein the pump device comprises a housing, a feed channel and a drain channel, wherein the feed channel communicates with the feed and the drain channel with the drain with respect to the flow of the lubricant; and wherein the pump device is driven by the flow of the lubricant in the feed; characterised in that the pump device comprises in the housing thereof: a worm pump with a conveying worm in the drain channel for conveying the returning lubricant; a turbine, which is driven by the lubricant being fed and standing under pressure (p), in the feed channel for driving the worm pump; the worm pump is formed from a tubular base body, which carries the conveying worm on its outer side; the housing has a bore in which the worm pump is rotatably mounted in bearings, wherein the space between the outer side of the base body and the inner side of the bore forms the drain channel, wherein the conveying worm protrudes into the drain channel, for conveying the returning lubricant; wherein the bearings and thus also the worm pump are positioned in stationary location in the interior of the bore with the aid of holding means, but are rotatably mounted; the helix of the conveying worm is inclined at an acute angle α relative to the tubular body in flow direction of the lubricant in the return; the holding means is constructed in the form of spoke wheels or apertured plates, which each extend in a plane perpendicular to the longitudinal axis of the bore in the housing and are connected at the periphery thereof at the inner side of the bore with the housing and which each carry at the inner side thereof, preferably coaxially with the bore, a respective one of the bearings for the worm pump; and the interior of the tubular base body forms the feed channel in which the turbine is arranged and connected with the base body to be secure against relative rotation. a worm pump with a conveying worm in the drain channel for conveying the returning lubricant; a turbine, which is driven by the lubricant being fed and standing under pressure (p), in the feed channel for driving the worm pump; the worm pump is formed from a tubular base body, which carries the conveying worm on its outer side; the housing has a bore in which the worm pump is rotatably mounted in bearings, wherein the space between the outer side of the base body and the inner side of the bore forms the drain channel, wherein the conveying worm protrudes into the drain channel, for conveying the returning lubricant; wherein the bearings and thus also the worm pump are positioned in stationary location in the interior of the bore with the aid of holding means, but are rotatably mounted; the helix of the conveying worm is inclined at an acute angle α relative to the tubular body in flow direction of the lubricant in the return; the holding means is constructed in the form of spoke wheels or apertured plates, which each extend in a plane perpendicular to the longitudinal axis of the bore in the housing and are connected at the periphery thereof at the inner side of the bore with the housing and which each carry at the inner side thereof, preferably coaxially with the bore, a respective one of the bearings for the worm pump; and the interior of the tubular base body forms the feed channel in which the turbine is arranged and connected with the base body to be secure against relative rotation.