PURPOSE: To have certain sweep of a thread and prevent interference with other works by allowing a mounting table to collide with the tapered surface of a pin to cause it to run away in the pin axial direction when a wiper arm is going to return after rotation backward.

CONSTITUTION: When a wiper arm 2 rotates ahead together with a mounting table 4 after thread cutting, the tapered part 4a of the mounting table 4 acts on a pin 3' of an arm 3a to depress the mounting table 4, which causes depression of a thread support wiper 7. Accordingly a gap is generated between the hook of a hook-equipped wiper 6 and a recess in the thread support wiper 7, and a needle thread is taken in this gap. When rotation of the mounting table 4 further advances, the action of the tapered part 4a on the pin 3' is disengaged, and the hook-equipped wiper 6 is restituted together with the mounting table 4 to nip the needle thread. When the wiper arm 2 returns upon rotating backward, the mounting table 4 collides with the tapered surface on the pin 3' to cause it to run away in its axial direction, so that the nipped needle thread will never be liberated.