What is the tolerance range for h6?
2 Answers
According to national standards, the tolerance grade for internal holes is represented by uppercase letters, specifically 360H6. The tolerance for an internal hole of 360H6 is φ360H6 (+0.036/0), with an upper deviation of +0.036 and a lower deviation of 0. The maximum limit size is φ360.036, the minimum limit size is φ360, and the tolerance zone is 0.036. Additional information: 1. National standards specify that the tolerance grade for external cylindrical shafts is represented by lowercase letters, while internal holes are represented by uppercase letters. This is used to distinguish between the tolerance grades of shafts and holes; 2. For example: What is the tolerance for Φ200-H7/h6? 200 represents the diameter. H7/h6 represents a clearance fit. The uppercase letter H is the fundamental deviation for the hole, 7 is the tolerance grade IT7, the lower deviation for the hole is 0, where h is the fundamental deviation for the shaft, and the upper deviation for the shaft is 0.
As someone who has been working in the automotive repair field for a long time, the topic of H6 tolerance range frequently comes up in my work. In automotive engineering, H6 refers to the tolerance grade for holes, commonly used in engine cylinder fits. The tolerance value isn't absolutely fixed and primarily depends on the actual size of the hole. To give a concrete example, a standard 50mm cylinder bore with H6 tolerance typically has a range of approximately ±0.009mm, meaning the dimension falls between 49.991mm and 50.009mm. This minute tolerance ensures smooth piston movement, preventing seizure due to insufficient clearance or increased vibration and noise from excessive gaps. I've personally measured this many times using a micrometer to check if the tolerance exceeds limits. If out of spec, it requires boring to repair or part replacement. Temperature changes can temporarily affect tolerance performance, like slightly larger gaps during cold starts, but long-term wear is the real issue. That's why regular maintenance is crucial—don't wait until the engine develops severe knocking sounds to take action.
