Sand Casting Tolerances

sand casting tolerances

Sand casting tolerances are sensitive to the materials used and the manufacturing process. International Organization for Standardization (ISO) Standard ISO 8062 for SG Iron castings made in machine-produced sand molds specifies general tolerances for metal alloy castings. Casting Tolerance (CT) 8–12 are the proper grades to use.

For the most part, sand casting cannot produce high-definition mirror finishes or parts with tight tolerances. Sand casting tolerance standards are typically discussed in the widely used industry, and these often fulfill the needs of the product design.

Table of Contents

Dimensional Sand Casting Tolerances

Below are the Sand Casting Tolerances for general industry standards.

Functional Dimensional

Functional Dimensional Tolerance
Inches ( Each Additional Inch Add ± 0.01" ) Millimeters ( Each Additional 25mm Add ± 0.025mm )
0~7 ±0.021 0~175 ±0.53
7~8 ±0.023 175~200 ±0.58
8~10 ±0.25 200~250 ±0.63
10~12 ±0.27 250~300 ±0.68
12~14 ±0.029 300~350 ±0.73
14~16 ±0.031 350~400 ±0.78
16~18 ±0.033 400~450 ±0.83
18~20 ±0.035 450~500 ±0.88
20~22 ±0.037 500~550 ±0.93
22~24 ±0.039 550~600 ±0.98
24~26 ±0.041 600~650 ±1.030
Additional tolerance across mould and core joints.
±0.0099" ±0.25mm

Non Functional Dimensions

Non-Functional Dimensions
Wall Thickness Tolerance ±0.008" ±0.2mm
Straightness/Flatness Tolerance (excluding localised pattern depressions) ±0.004" per inch 0.1mm per 25.4mm
Angular Tolerance ± _° UP to 3" ± _° UP to 7.60mm
Typical Surface Finish 80 MICROINCHES 2.0 MICROMETRES
50% Additional Tolerance up to 5.000" 127mm
33% Additional Tolerance above 5.000" 127mm

For the sand casting services from Leisheng Machinery, We can do better casting tolerances

Dimension Tolerances & the Factors that Affect Them

Tolerances in dimensions refer to the allowable range of final product variations from their nominal dimensions. The degree to which tolerances can be satisfied is affected by several variables, including but not limited to the following:

Casting Cores and Design

Tolerances that are possible depending on several factors, including the complexity of the casting design (particularly the addition of cored passages). The capacity to create cores that resist bowing or sagging due to their own size or shape and the pressure of surrounding metal may limit the accuracy and precision of cored passage dimensioning.

Types of Dimension

Different sorts of dimensions exist depending on whether they are determined by the mold alone, the core alone, or a mix of the two, with and without the effect of the separation line.

Pattern and Core Box Equipment

The pattern used to make the casting significantly impacts the degree to which the casting’s dimensions match those of the design. Since the steel will contract as it cools in the mold, the pattern must be built with accurate proportions. And it’s not uncommon for foundries that use the same pattern to create castings with somewhat differing tolerances.

In order to make the most efficient use of the foundry’s experience with impeded contraction, it is advised that the foundry has chosen to perform a certain casting and also have control of pattern construction.

When deciding which materials to use for a pattern, it’s also essential to consider how long it will be used in manufacturing. Softwood patterns will have larger dimensional differences from casting to casting within a lot than metal patterns will.

Dimension Length and Casting Weight

Dimensional differences are highly sensitive to the casting’s weight. Process capability in terms of dimensional tolerances is nonlinearly affected by casting weight and dimension length.

Dimensional and Gaging Upgrading

Tolerances for as-cast surface dimensions are negotiated between the castings’ maker and the buyer. However, the tolerances chosen should be comparable to the process capabilities for the specific operating conditions being considered to reduce the rejection of castings due to dimensional reasons. When dimensional tolerances are tighter than what can be achieved during production, additional processing is needed to improve the casting’s quality.

Mold Processes

The manufacturer and purchaser of the castings agree upon the tolerances for the castings’ as-cast surface dimensions. To reduce casting rejection owing to dimensional reasons, the tolerances used should be comparable to the process capabilities for the particular operating conditions being evaluated. Additional processing is required to increase the casting quality when the dimensional tolerances are tighter than what can be achieved during production.

Significance of Sand Casting Tolerances

Standards vary depending on the type of material or manufacturing method being used. Therefore, positional and length (per inch) tolerances, material grades, customer needs and specs, and other factors are all considered and evaluated throughout each process. Additionally, each association has its own set of rules and regulations.

Quite a few outcomes are possible when tolerances aren’t met.

In the end, they all have an impact on expenses, and none of them are really pleasant. It might be minor if you’re lucky. But usually, it’s a big deal. Although there are many steps and factors to think about, the key to making the best choice is to work with a reliable collaborator who is familiar with the nuances involved.

About Us

Leisheng Machinery is a professional manufacturer in China since 1991, founded by Li, which is a famous china enginner. At the very beginner and we only focus on CNC Machining. And in 2006, our capabilities extend to casting, including investment casting, aluminum die casting & sand casting. In 2008, we build our another fatory, and our capabilities expend to metal forging.

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