Although quenching in oil reduces failure, it is not suitable for modern swords that are meant to become a work of art because it cannot achieve a fine Hamon (blade pattern), apart from its sharpness.
油で焼きを入れると失敗は少ないが、刃文に冴えを出せず斬れ味は別として、美術工芸品を志向する現代刀には不向きだからである。