Ar un adeg, y Dyrnwr Mawr oedd y peiriant amaethyddol mwyaf ei faint ai gymhlethdod ar y fferm, ac maer gyfrol hon yn adrodd hanes y peiriant ar diwrnod dyrnu. Cynhwysir gwybodaeth dechnegol ac amaethyddol am y peiriant, ynghyd â manylion am natur gymdeithasol y gweithgaredd pwysig a chofiadwy hwn. 45 llun du-a-gwyn. At one time, the Thresher was the largest and most complex farm machine, and this volume relates the story of the machine and the threshing day. Technical and agricultural information is included together with details re the social nature of this important and memorable activity. 45 black-and-white images.