The article presents the quality assessment of the operation of HEID technological line threshing unit in SAATBAU Sp. z o.o. company in Środa Śląska. Evaluation of the CIMBRIA abrasive machine was made based on the macro and micro damages of seeds, which were made after threshing and through determination of seeds germination capacity and energy. Tests were carried out for five corn varieties: Bosman, Sl Normo, Odilo, Okato, Wikana. The calorymetric method was applied for determination of mechanical damages to seeds. The biggest macro-damages were reported at the level of 4.2% and micro-damages at the level of 14.5%. The increased values of damages occurred after threshing. The highest germination capacity was 96%. On this basis it was stated that the quality of the operation of the threshing unit was within the norm.