Casting dimensional tolerance refers to the difference between the two allowable limit sizes of the nominal size of the casting. Within these two allowable limits, castings can meet the requirements of processing, assembly and use.
Casting dimensional tolerance plays a vital role in ensuring the high quality and precision of castings. It allows for a certain degree of variation between the nominal size of the casting and its actual size, making it possible to produce parts that are both functional and aesthetically pleasing.
International standard ISO 8062-1994 second edition "Casting dimensional tolerance system". It is the basis for the design and inspection of the size of castings, which specifies the dimensional tolerances of various casting metals and alloys produced by sand casting, metal casting, low pressure casting, pressure casting, investment casting and other methods, including the basic dimensional tolerances of castings. Tolerances specified are tolerances normally achieved under normal production conditions, divided into 16 grades from fine to coarse and named CT1-CT16(CT is short for Casting Tolerances).
The basic size of the casting is the size given on the casting drawing, which shall include 1/2 of the required machining allowance and tolerance. Tolerances should be distributed symmetrically. If there are special requirements, it can also be arranged asymmetrically, and should be indicated on the drawing or specified in the technical document. The wall thickness dimensional tolerance can generally be reduced by one level, for example, the general dimensional tolerance on the drawing is CT10 level, then the wall thickness dimensional tolerance is CT-11 level. Use tolerance class code on the drawing, such as GB/T 6414-CT 10. When you want to limit error type values, you should indicate the value of the largest error type.
