They are three, who has a relative movement with whom, who is relatively static between them? What are their order from inside and outside?
Generally speaking, the shaft and the bush or the sliding bearing are relatively moving, and the bush or the sliding bearing is relatively static with the sitting hole or the bearing seatFrom the inside to the outside, the order is: the shaft, the innermost, the bush or the sliding bearing in the center, and the outside is the mounting hole or the bearing seat
The bush or the bearing are all objects, and the axle diameter is a concept of distance
The bearing bush is a kind of plain bearing. The axle diameter refers to the diameter of the axle.
