raising and lowering of bit是什么意思

网络释义

1)raising and lowering of bit,钻头上下跳动2)jumper,上下跳动钻孔机3)bit bounce,钻头跳动4)dancer roller,上下跳动滚轮5)bit bounce,钻头回跳6)roll up/drill down,上钻/下钻