下列加工工序中 不是自为基准加工的。 Which of the following operation is not based on self-datum principle
A.
浮动镗刀镗孔 A floating boring cutter bores holes
B.
无心磨床磨外圆 A centerless grinder grinds the cylindrical surface
C.
齿轮淬火后磨齿面 Grinds the tooth surface after quenching of the gear
D.
浮动铰刀铰 The floating reamer reams the holes