This invention relates to a system for mounting tooth-carrier sectors on a cutter wheel or a milling-cutter drum (or coal-cutter drum) permitting the rapid mounting of the sectors, as well as a change in the direction of operation of the wheel or drum about its axis. The supports (2) attached to the wheel (1) by their base are delimited by two lateral surfaces (4) and by one upper surface (3), which rest on the yoke-shaped base of the tooth-carrier sectors (8). The support (2) has a shape which is symmetrical with respect to its axis (7), and its lateral surfaces (4) form with the perpendicular to the axis (7) an angle (.alpha.) which is less than 90.degree. at their outer end. The sector (8) is closed on the side which rests against the front surface (4) during operation. The sector (8) is attached to its support, for example by means of an elastic dog (11).

A tool assembly for mining machines and particularly for coal planes or coal cutting machines comprises a cutter which has a shank portion which is engaged to a seat of a size comparable to the shank portion of a cutter holder and it is held in that position by a locking pin which extends through aligned bores of the holder and the shank portion which may be retracted into a knockout slot defined in the shank portion which is closed on each side by a portion of the cutter holder in an arrangement in which the locking pin may be retracted into the knockout slot for removal of the cutter.

A floor cutter bit for a coal plough has a body carrying a pair of hard metal plates which define a coal face cutting edge and a floor cutting edge. A hard metal pin locates between the plates and receives end zones of the plates within recesses.

A mining tool for the breaking-down of minerals, particularly coal. The mining tool includes a chisel with a chisel shaft with a receiving bore and a chisel holder with an insertion bore. The bores are in alignment when a locking bolt is driven into the bores. The locking bolt is a mandrel screw with a threaded portion which over its length includes a sharp thread and a trapezoidal thread. The circumferential surfaces of the trapezoidal thread form a driving-in cone. The mandrel screw can be easily driven into the receiving bore which includes a chuck. In addition, because of the sharp thread, the mandrel screw can be unscrewed quickly, so that a quick chisel exchange is possible.

A tool for a mineral winning machine, more usually a plough, has a flat plate-like body with a bore containing a nozzle insert and preferably a hard metal cutting region or blade is also provided on the body. High pressure water is conveyed through the bore and nozzle insert to discharge as a jet which is directed to impinge against the mineral or coal face to effect a cut therein hydraulically. The nozzle insert has its discharge mouth in a protected position inside the body.