在维修和保养拖拉机中，遇到最多的操作是拆装螺纹件，如拧螺栓、螺母和螺钉等。拧螺纹件虽然简单，但其中也有许多学问，如操作不当，就会造成机件损坏，或引起机器故障。（１）选用工具要合适。选用工具不合适容易造成六角（或四角）螺帽的棱角磨圆和螺钉的槽削平，使拆... In the repair and maintenance of tractors, the most encountered operation is the removal of threaded parts, such as bolts, nuts and screws. Although the screw thread is simple, but there are many learning, such as improper operation, it will cause damage to the parts, or cause machine failure. (1) Selection of tools to be appropriate. Optional tools are not suitable for easy to cause hexagonal (or four) nut rounded corners and screw slot flat, so demolition ...