The narrator describes the headman's terrible dental situation. The bad tooth is all the way at the back of the headman's mouth. Luo inserts a makeshift drill made from the tailor's sewing machine into the headman's mouth as the tailor works the treadle of the machine and begins to drill into the tooth. The headman screams in pain and accuses Luo of nearly killing him. Luo explains that a real drill spins much faster, and the slower the drill spins the more painful it will be. The headman instructs Luo to try again, but the pain is again too much for the headman to hold still.
This horrific situation illustrates one of the worst-case scenarios of repressing knowledge and education. Further, it shows that the repression harms the peasants, the very people that the government claims to revere. The fact that Luo agreed to fill the headman's tooth is a demonstration of loyalty to the narrator.
Luo asks the headman to rinse his mouth and then suggests that in order for the dental work to progress, the headman will need to allow them to strap him down to the bed. The narrator is dumbfounded, but the headman agrees. The tailor is tasked with keeping the headman's head still, while the narrator takes over working the treadle of the sewing machine. Luo attacks the tooth with the needle. The narrator feels suddenly sadistic and slows down the treadle. Luo appears complicit as the needle slows down to one or two rotations per second and chisels into the tooth.
The headman's cooperation suggests that some things are more important than the enforcement of Communism—the universal experience of pain, for example. When the narrator is allowed such a degree of power, he runs with it. This is a turning point for the narrator's coming of age, as torturing the headman like this is an experience in which the narrator takes individual action against the world.