An Nodachi was a type of traditionally made Japanese sword used by the samurai class of feudal Japan. To qualify as an ōdachi.
The sword in question would have a blade length of around 3 shaku 90.91 cm however, as with most terms in Japanese sword arts, there is no exact definition of the size of an ōdachi.
This video by AWE me details how a Japanese style sword is forged from start to finish.The method of polishing is also different.
Because of their size, Nodachi are usually hung from the ceiling or placed in a stationary position to be polished, unlike normal swords which are moved over polishing stones.