Standard (Default) Tolerances
These are general tolerances. Used when no specific tolerance is provided. Many workshops use ISO 2768 or ASME Y14.5 standards. The most common default is +/- 0.1 mm. Standard tolerances are suitable for basic, non-critical parts. They help reduce costs and speed up production.
Two-sided Tolerances
This type of tolerance allows for a deviation between the values on both sides. For example, 10.00 mm +/- 0.05 mm means the part tolerance ranges from 9.95 mm to 10.05 mm. It is flexible. It is typically used in applications where proper fit is not required but good control is needed.
One-sided Tolerances
This tolerance allows for only one-sided variation. For example, 10.00 mm +0.00/- 0.10 mm. It can be smaller, but never larger. It can be useful when components should not be too large. This is typically used for press-fit or sliding parts.
Limit Tolerances
Limit tolerances provide a range instead of using (+) and (-) signs. For example, 9.90 mm to 10.10 mm. This indicates the minimum and maximum permissible dimensions. This simplifies inspection and avoids errors when reading drawings.
Geometric Dimensions and Tolerances (GD&T)
GD&T is a system for controlling shape, angle, and position. It's not just about controlling volume. It uses symbols for flatness, parallelism, and upright posture. GD&T ensures parts perform well in assembly. It's very useful in complex or high-performance components. However, inspection is slower and machining costs are higher.
Different tolerances have different uses. This depends on the fit of the part, your willingness to spend, and the function of the part. Use simple tolerances when possible. Only maintain tighter control over the required characteristics. This helps you achieve good results at a lower cost.
