A blade assembly is connected to a robot arm for transmission of semiconductor chips and includes a blade, a top cover, a bottom cover, and two pivot units each including a pivot arm, a first bearing, and a second bearing. Thus, the positioning flange of the mounting ring of the pivot arm is sandwiched between the first bearing and the second bearing and the inner washer is sandwiched between the inner ring of the first bearing and the inner ring of the second bearing, thereby preventing the first bearing from pressing and jamming the second bearing due to a pressing action of the urging cap, so that the pivot arm is pivotable smoothly and stably.