销轴驱动滚子方补芯具有如下特点:

　　1. 可以边转动边上提或下放钻具；2. 由于是整体式，不会飞出伤人；3. 在传动销还没有装入以前，就使用在引入套的浮动环，使补芯很快地对准锥面的中心，达到节省时间的目的。方钻杆与滚轮为滚动接触，因而摩擦力小，钻压准确，提高使用寿命。msn:xiaoyouloveyou@hotmail.comthe pin drive roller kelly bushing provides the following advantages:1. pulling out or feeding off string can be done while rotating;2. because fo its integral construction , it can not fly out and hurts you,3. the bushing is easily installed into the master bushing, maintaining good alignmentthe contact between kelly and roller is rolling contact, so friction is lower, and weight on bit is accurate.