加工中心的加工顺序，应先铣面后铣孔；在孔系加工中，先加工小孔，后加工大孔。
查看答案
中心钻分为A型、B型等，A型不带护锥，B型带护锥。
A. 对
B. 错
主轴转速1350r/min、钻头直径Ø12，求切削速度
A. 50.9m/min
B. 60m/min
C. 55m/min
D. 90m/min
“I don’t like to travel. ”“Have you ever _____ in an airplane?”
A. flying
B. flew
C. flowed
D. flown
The center of gravity of the human body ______ behind his joint.
A. located
B. locating
C. to locate
D. is located
微信支付 
支付宝支付