Underholding type large intercept coal-cutting drum of raising lump coal rate

This utility model discloses an undermine large cross mining drum with a promotion of lump coal rates. The said mining drum comprises a cabaret, a barrel, auger flights, gear seats and cutter bits. The stub distance of the cutter bits equipped on the auger flights is 100-250mm and the auger flights are provided with certain stubs, each provided with 2-4 successive cutting cutter bits with a length of more than 100mm and is equipped in the direction of drum axis with an angle of 90 degree. The stub distances of adjacent cutter bits are either the same or different with each other. This utility model is substantially suitable for yolk coal beds with a coal rigidity of less than 1.5 and changes the distribution amount and collating sequence of the cutter bits to form undermine cutting by increasing the cross of the spiral drum cutter bits. The cutter bits cut the coal wall into a plurality of cannelures due to large cutter bits cross and small cutting influence of adjacent cutter bits, and the cutter bits on every stub repeats cutting to deepen the cannelures. With the spilting influence of the cutter bits, the coal between the cutter bits fall into pieces in the cranny direction and large blocks of coals can be produced between two cutter bits, thereby increasing the grain diameters of lump coals and promoting lump coal rates.