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1 鑽床以25m/min的速度 ,鑽一ϕ25mm的孔,如孔深自工件表面至孔頂尖為21mm,進刀量為0.2mm/轉,則實際鑽孔時間為
A 0.23min
B 0.33min
C 0.43min
D 0.53min

N = 1000VπD

= 1000×25π×25

= 318 (rpm)

T = Lf×N

= 210.2×318

= 0.33 (min)