variety of sizes may be used in practicing the invention such as for example semiproduction models having a working capacity of at least 40 pounds as well as production models having a working capacity of 400 pounds or above for example the adjustable partition allows a decrease in batch size in a semi production model from about 40 pounds down to about 2 pounds referring to the drawings in fig1 coating drum 1 comprises perforated cylindrical peripheral surface 2 having annular side wall portions 3 and 5 side wall 3 defines a wide opening 4 for introducing tablets and coating material into drum 1 side wall 5 together with circular plate 6 encloses one end of the drum 1 which may be rotated by means not shown affixed to plate 6 and may be supported by rollers not shown at the lower portion of the drum fig2 shows an adjustable partition fastened in place by bolts extending through the perforations in the coating drum and dividing the drum into inactive zone b and coating zone a circular disk 15 interconnects truncated sectors 8 and 9 with bolts 14 and the truncated sectors in turn are secured to the perforated peripheral surface 2 of.