Hlau ntug rounding yog cov txheej txheem ntawm tshem cov ntse los yog burr npoo los ntawm hlau qhov chaw los tsim ib tug du thiab nyab xeeb nto. Slag grinders yog cov tshuab ruaj khov uas zom cov hlau seem thaum lawv tau noj, tshem tawm tag nrho cov slag hnyav sai thiab zoo. Cov tshuab no siv cov hlua sib tsoo thiab txhuam kom siv zog ua kua muag los ntawm qhov hnyav tshaj plaws ntawm cov pob zeb.