Unilateral tolerance is a type of dimensional tolerance that allows variation in only one direction from a specified nominal value. In other words, the allowable deviation is only in one direction—either positive or negative, but not both.
### Example
Suppose you have a shaft with a nominal diameter of 50 mm, and you specify a unilateral tolerance. You might specify:
- **Nominal Diameter**: 50 mm
- **Unilateral Tolerance**: +0.05 mm / -0 mm
In this case, the shaft diameter can vary as follows:
- **Maximum Diameter**: 50 mm + 0.05 mm = 50.05 mm
- **Minimum Diameter**: 50 mm (since there is no allowance for negative deviation)
So, the diameter of the shaft can be anywhere between 50 mm and 50.05 mm. This is an example of a unilateral tolerance where the tolerance is only in the positive direction.
Unilateral tolerances are used in cases where one direction of variation is more critical or where manufacturing processes can only control one direction of variation effectively.