toleranssiraja

Toleranssiraja is a Finnish term used in engineering and manufacturing to describe the permissible range of variation for a dimension or parameter. It defines the upper and lower limits within which a part must lie to be considered acceptable. The interval between the lower limit (alaraja) and the upper limit (yläraja) forms the tolerance zone, and the numerical difference between these limits is the tolerance value (toleranssi).

In practice, toleranssiraja ensures that parts from different manufacturers will still fit together and function as intended, even with production variations. It influences manufacturing cost, inspection effort, and product reliability. Tolerances can be bilateral, allowing variation on both sides of a nominal size (for example, 10.00 mm with ±0.05 mm), or unilateral, permitting variation on only one side (for example, a hole size of 10.00 mm +0.00/−0.05 mm).

Toleranssiraja is commonly specified on technical drawings and is aligned with international standards. In metric systems, ISO tolerance classes (such as H7, g6) provide standardized limits for holes and shafts, while numerical dimensioning may include explicit upper and lower limits. The choice of tolerance depends on function, fit, manufacturing capability, and inspection methods.

Geometric tolerances and surface quality have separate concepts for permissible variation, but they are often coordinated with dimensional tolerances to ensure overall part interchangeability.