The size of coal fragment cutoffs by cutting mechanisms is an important index of coal mining. The larger the coal fragments, the less the dust, the lower the specific energy consumption and the higher the benefit. Therefore, a coal fragment size model was formulated in order to obtain large coal fragments in the cutting process, which considered the effect of pick arrangements (sequence and Punnett-square), helix angle, advancing velocity and the cutting line space of cutting mechanisms. Moreover, the effect of the above parameters on the size of coal fragments was analyzed in theory, which was validated by the cutting experiments correspondingly conducted using 8 different helix drums. The theoretical and experimental results-indicate that the coal fragment cutoffs by Punnett-square drums are larger in size and more uniform in size distribution than by sequence drums; the size of coal fragments, increasing with the advancing velocity and the cutting line space, is almost unaffected by helix angle; the effect of advancing velocity and the cutting line space for Punnett-square arrangement is greater; the effect of cutting line space on coal fragment mass percentage below 1 cm is greater than that of advancing velocity. (C) 2014 Elsevier B.V. All rights reserved.