There is a national standard for tolerance grade of castings in China. This national standard applies to malleable cast iron, gray cast iron and nodular cast iron you mentioned. Generally, manual modeling can achieve the level of CT 1 1, ordinary machine modeling can achieve the level of CT 10, and high-pressure forming should reach the level of CT9. Compared with other dimensions of the same casting, the wall thickness tolerance of the casting can be relaxed by one grade. The specific tolerance of a certain size can be obtained according to the tolerance grade and nominal size of the casting. Please refer to the foundry manual (Volume V Foundry Technology) or the national standard GB/T 64 14- 1999.