26 this enclosure 44 is adapted to be evacuated by the suction pump 45 so that in use during pulverizing operations and during subsequent cleaning operations when the sample tray 46 is removed dust and other waste material collected in the enclosure 44 is removed in a suitable filter associated with the suction pump 45 in use for example a geological sample is introduced into the feed chute 34 and the lid 47 is then closed the rotary anvil 12 is rotated until the sample has been pulverized to the desired particle size this pulverized sample flows outwardly between the mating faces 36 of the anvils 12 and 13 into the cowl 26 for discharge into the tray 46 after the sample has been pulverized the cleaning mode is actuated either automatically upon removal of the sample tray 46 or manually if a cleaning mode button is pressed upon commencement of the cleaning cycle the lock assembly 19 is released and the non rotary anvil 13 is retracted a set amount as preset by the tailstock location sensor assembly 48 to enable material remaining between the anvils and within the cowl to be flushed out by air blast or other means introduced at a suitable pressure from the plenum chamber 41 this air blast with assistance from the evacuated enclosure 44 will remove substantially all foreign material from the anvils 12 and 13 and the cowl 26 during the cleaning cycle the rotary anvil 12 may be rotated intermittently in opposite directions this is controlled by a selector switch on a control panel which indicates the number of reversals of rotation of.