Abstract: A stump cutting machine includes a rotatable cutter disc having a plurality of cutter tools on opposite sides thereof, and each of the tools includes a bit holder having half sections for clamping the shank of a bit therebetween in aligned slots formed in the mating clamping faces of the half sections. The channel-shaped slots extend at an angle to the cutter disc and to the clamping faces of the half sections and thus position the bit at an angle to the cutter disc. The bit holder may be turned between two positions 180.degree. apart, and the bit will extend outwardly relative to the disc and inwardly relative to the disc in the other position. A pair of bolts extend through the holder half sections in the disc to connect the two holders on the disc on opposite sides thereof. The effective depth of the slot is less than the thickness of the bit shank to insure clamping action by the bottom walls of the slot when the half sections are drawn tightly together by the bolts.