1. The large hexagonal bolts must be able to pass through the bolt holes at will. Oxygen cutting cannot be used for reaming the bolt holes, and the amount of reaming should be carried out according to the engineering design. The diameter of the hole after reaming must be less than 1.2 d. 2. Every time the operation reaches 12,000km, the large hexagonal bolts need to be maintained at the second level. All hex bolts should be equipped with an oil pan, and then check the condition of the piston pins. If the distance between the piston pins is too large, replace them, and replace the connecting rod bolts at the same time. If it is found that the engine has abnormal noise and unstable operation during daily operation, it also needs to be inspected in time. 3. Every time a repair is performed, the new connecting rod bolts must be checked again. It is also necessary to check the guiding position of the hexagon bolt, the top of the thread head, etc., whether there are pits or cracks in these positions, and whether the tooth pitch and the tooth profile of the thread are normal. If there are any abnormalities in the above parts, it cannot be used continuously. 4. When installing the connecting rod bolt cover, it must be carried out with a torque wrench. When tightening, it must be in accordance with the specified specifications, and the torque should not be too large or too small. 5. The large hexagonal bolts of the crankshaft must be manufactured by supporting facilities. 6. After the large hexagonal bolt is assembled with a spherical joint, the spherical joint must be firmly connected with the bolt, and the bolt must be screwed into the bolt ball, so the size of the external thread should exceed 1.0d, and the joint area should not be loose or gaps. 7. The friction surface that must be connected by large hexagonal bolts should be clean and dry, without welding slag, burr, welding spatter, compound scale, shiny, waste, etc. Unless there are special circumstances, it cannot be painted.