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1 欲攻內螺紋時,若螺紋規格為3/4-10UNC-2B,則所鑽的孔徑約為
A 14.5mm
B 15.5mm
C 16.5mm
D 17.5mm
攻螺絲之前的鑽孔直徑=螺紋外徑-節距=3/4-1/10=13/20”=16.51mm