Casting size tolerances are applied to all the components produced by casting. This is to ensure that the components meet the specifications of the casting process and are of a high quality. Tolerances for size and geometry are usually taken from metrology information databases.
The tolerance of a casting size is determined by the type of material being cast, the moulding process used, and the design of the component. Generally, casting size tolerances are divided into two categories: basic and strict.
Basic tolerances are usually specified during the design process, and are necessary to ensure that the components meet the general specifications of the casting process. These basic tolerances are usually relatively large, and can often vary significantly between different designs.
Strict tolerances are usually specified during the production process, and are necessary to ensure that the components meet specific design specifications. These strict tolerances are usually much tighter than basic tolerances, and must be achieved in order to provide the best quality components.
Casting size tolerances are typically graded according to six grades. Grade 1 is the most stringent, with Grade 6 being the least stringent. Grade 1 is usually used for components that must be perfectly accurate, while Grade 6 is often used for components that will not be used in a critical application.
Grade 1 tolerances usually require a minimum size, and a maximum size, with a tolerance of only 0.001 inches. This means that the size of the component must be within the specified range, and there can be no variation in size from the specified size.
Grade 2 tolerances require a minimum size, and a maximum size, but with a slightly increased tolerance of 0.002 inches. This allows for a slight variation in size from the specified size.
Grade 3 tolerances allow for a minimum size and a maximum size, but with a slightly increased tolerance of 0.005 inches. This allows for a larger variation in size than Grade 2 tolerances.
Grade 4 tolerances allow for a minimum size and a maximum size, but with a slightly increased tolerance of 0.010 inches. This allows for a large variation in size from the specified size.
Grade 5 tolerances allow for a minimum size and a maximum size, but with a slightly increased tolerance of 0.020 inches. This allows for a considerable variation in size from the specified size.
Grade 6 tolerances allow for a minimum size and a maximum size, but with a slightly increased tolerance of 0.050 inches. This allows for a large variation in size from the specified size.
When choosing the grade of tolerance for casting size, it is important to consider the design specifications, the application, and the quality requirements. The higher the grade of tolerance, the more accurate the component will be. However, higher grade tolerances can increase the manufacturing costs and the time needed to manufacture the component.
