JPS618240B

For cooling the bits (1) of a cutting machine, nozzles (22) for cooling water are provided. The bit (1) is supported for axial shifting movement and can when being loaded exert a stroke for the path (a) in direction of the arrow (4). A coupling member (9) transmits the movement of the bit (1) to a shutoff valve (7) blocking the supply of water in unloaded condition of the bit and giving free the supply of water whenever a predetermined cutting pressure is exceeded. The restoring force of the bit (1) to return the same in its starting position in unloaded condition is provided by a spring (5) and by the water pressure and is rated in correspondence with the minimum value of the cutting pressure. The restoring spring (5) is supported against an adjustable abutment (30, 31) which can be fixed in position during operation so that the restoring force can be adjusted.