A coal-crushing machine in which the roll teeth crack downward on the lump and the roll itself compresses the coal against the breaker plates. Teeth of two or more designs are used generally on the same roll, some for the slugging, cracking, or blow action and others for a pulling and splitting force. The breakers are not easy to stall by choking, since they will pass a heavy overload, partly because of the action of a relief mechanism, with which they are all equipped.