The flat in the supporting axle of the train wheel side frame is very difficult to process with ordinary milling lathe, and processing efficiency is very low.

火车车轮侧架支撑轮轴处的平面加工用普通铣床加工很困难，而且效率很低。

youdao

The buzz in the city has been manic, and even going into the stadium to train, there have been hundreds, perhaps thousands, of people milling around the ground.

BBC: Big day out