Tolerances in Mining Engineering

In mining engineering equipment and parts, tolerances, as with all part manufacturing, is influenced by the material used to produce the part as well as the function of the part. From iron castings to steel fabrications, tolerances can be applied to any dimension.

Commonly used terms involving dimensional tolerances in mechanical component tolerances:

1. Basic Size:
   This involves the nominal diameter of the bolt or shaft and the hole. Generally, this will be the same for both components.
2. Lower Deviation:
   Lower deviation refers to the basic size and the minimum possible component size.
3. Upper Deviation:
   This refers to the basic size and the maximum possible component size.
4. Fundamental Deviation:
   A form of allowance, fundamental deviation involves the minimum difference in size between a component and the basic size. This is identical to lower deviation for holes and upper deviation for shafts. In cases where fundamental deviations are more than zero, the bolt will be smaller than the basic size, with the hole always being wider.

The tolerances of iron castings are dependent on both the material being casted as well as production method used. Below a table containing casting methods, materials and casting grades:

Note: You can click on the table to view a larger image.

Learn more about Metal Casting or visit the following pages on our website for more in-depth information:

1. Sand Casting
2. Permanent Mold Casting
3. Investment Casting

You can also learn more about the materials used in mining engineering as well as the different iron castings manufactured by visiting our Materials used in Mining Engineering Castings and Fabrications page.

Casting Dimension Tolerance Grade CT in Millimeters:

Note: You can click on the table to view a larger image.

Note: Numbers rounded off to nearest decimal.

Given as a Total Tolerance on value, i.e. 95 +/-1.1 is grade CT9.

Casting Dimension Tolerance Grade CT in Inches:

Note: You can click on the table to view a larger image.

Note: Numbers rounded off to nearest decimal.

Given as a Total Tolerance on value, i.e. 3.740 +/- 0.043 is grade CT9.

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Further Suggested Reading:

• Materials used in Mining Engineering Castings and Fabrications
• Avoiding Porosity in Mining Engineering Castings
• Advantages in Shipping from China