1. Adopt two center holes for positioning and clamping
Generally, the important outer round surface is used as the rough reference for positioning, and the center hole is processed, and then the center hole at both ends of the shaft is used as the precise reference for positioning. As far as possible to achieve unified benchmark, benchmark overlap, mutual reference, and realize the installation of multiple surfaces. The center hole is a unified positioning and inspection reference for the workpiece processing. Its own quality is very important, and its preparation is relatively complex. It is often used to support the journal positioning, the car (drill) center cone hole; Then to the center hole positioning, fine round car; External circular positioning, coarse grinding taper hole; To the center hole positioning, fine grinding outer circle; Finally to support the outer circle of the journal positioning, fine grinding (scraping or grinding) cone hole, so that the accuracy of the cone hole to meet the requirements.
2, with the outside surface positioning clamping
For hollow shafts or short shafts where it is impossible to locate a central hole, the shaft's outer surface can be used for locating, clamping and transferring torque. Generally, general fixtures such as three-jaw chucks and four-jaw chucks are used, or all kinds of high-precision special fixtures for automatic centering, such as liquid plastic thin-wall centering jigs and diaphragm chucks.
3, with a variety of plug or pull rod mandrel positioning clamping
When machining the outer circular surface of hollow shaft, various plugging heads or pull rod mandrel with central hole are commonly used to install the workpiece. Small cone holes are often plugged; Large conical holes are often covered by a tie rod mandrel.