Jin Dajian is an engraver living in Jizhou whose exquisite skill in carving seals, stone tablets and designs on jade earns him the nickname "Jade Armed Craftsman". He has known Wu Yong of Liangshan before he joins the stronghold.
When Song Jiang is in Jiangzhou, where he is exiled to as punishment for killing his mistress Yan Poxi, he could move in and out of prison freely with permission of the chief warden Dai Zong, who is a friend of Wu Yong. One day he gets drunk in a restaurant alone. Lamenting his misfortunes, he writes a seditious poem on a wall in the restaurant, which he forgets the next day. Huang Wenbing, a petty official, discovers the poem and reports it to Cai Jiu, the governor of Jiangzhou, leading to Song being locked up and flogged. Cai Jiu orders Dai Zong to take a letter to his father Grand TutorCai Jing in the imperial capitalDongjing as he needs the latter‘s advice on how to deal with this matter. Dai Zong passes by Liangshan and is drugged in an inn of the stronghold run by Zhu Gui. Zhu discovers Cai Jiu's letter on Dai and takes him to the bandit chiefs, who learn from Dai the perilous situation of Song Jiang. Wu Yong suggests fooling Cai Jiu to send Song to Dongjing, so that the bandits could rescue him while he is on the way. To forge a letter from Cai Jing requires the help of the scholar Xiao Rang, who could imitate the Grand Tutor's handwriting, and the craftsman Jin Dajian, who could replicate Cai's personal seal. Dai Zong travels to the homes of the two men, who are told their skills are needed for the renovation of a temple. They are lured to the vicinity of Liangshan, where they are taken to the stronghold. Finding themselves trapped, Jin and Xiao have no choice but join Liangshan. They create the fake letter as instructed by Wu Yong. But the seal affixed to the letter happens to be one not appropriate for correspondence between fathers and sons. The letter fools Cai Jiu but not Huang Wenbing, who points out the giveaway. Cai Jiu orders Song Jiang and Dai Zong be executed. Meanwhile, having realised the mistake, Wu Yong sends many chieftains to Jiangzhou, where they save the two just when they are going to be beheaded.
Campaigns
Jin Dajian is placed in charge of all the engraving works, particularly carving of seals, after the 108 Stars of Destiny came together in what is called the "Grand Assembly". He participates in the campaigns against the Liao invaders and rebel forces in Song territory following amnesty from Emperor Huizong for Liangshan. In the attack on Jingnan in the campaign against Wang Qing, Xiao Rang, Jin Dajian and Pei Xuan are captured by the enemy. The three refuse to turn traitor under torture. They are freed when Xiao Jiasui and others revolt against Wang, causing Jingnan to fall. Before the Liangshan heroes start their last expedition, which targets Fang La, Emperor Huizong summons Jin Dajian to the palace, where he is retained to serve as an imperial craftsman. He remains in that job for the rest of his life.
