What is the H7/h6 fit?
3 Answers
H7/h6 is the tolerance fit code for mechanical components in the industry. H7 refers to the tolerance zone code for the hole it fits with, while h6 represents the tolerance zone code for the outer surface of the bearing (where the bearing acts as the shaft when fitting with the hole). The outer and inner diameter dimensions of the bearing vary, so while the tolerance zone H7/h6 is the same for different bearing sizes, the actual tolerance values differ. The numerical values of H7/h6 are related to the diameter—the larger the diameter, the larger the H7/h6 value, and vice versa. The functions of a tire are: 1. To transmit driving force, braking force, and steering force to enable vehicle operation; 2. To support the vehicle load; 3. To reduce and absorb vibrations and impact forces during driving, preventing severe vibrations from damaging automotive components. Methods for tire maintenance include: 1. Regularly checking tire pressure; 2. Periodically inspecting tires for bulges, cracks, cuts, punctures, or abnormal wear; 3. Removing foreign objects such as stones, metal pieces, or nails from tire treads; 4. Performing wheel alignment or tire dynamic balancing.
You're asking about the H7/h6 fit? I often see this tolerance pairing in car repairs, and it's quite reliable. H7 refers to the hole's size range, which is relatively loose and easy to machine, while h6 refers to the shaft's size, which is very precise with deviations in the negative zone. As a result, when combined, the shaft is smaller and the hole is larger, creating a slight clearance. This type of fit is most commonly used in automotive engine connecting rods or crankshaft ends, allowing parts to slide freely without jamming. The tolerance numbers 7 and 6 represent precision grades—the smaller the number, the tighter the fit, so h6 is more accurate than h7. This fit ensures the engine runs smoothly, reducing noise and wear, but it requires regular checks. If the clearance is too large, the operation will produce a rattling sound; if it's too small, thermal expansion may cause seizure. It's recommended to use a micrometer to measure and ensure it stays within the factory's safe specifications for long-term reliability.
In automotive design work, we designate the H7/h6 fit as the standard hole tolerance plus shaft deviation. The H7 hole deviation is positive, allowing for a larger size, while the h6 shaft deviation is negative, resulting in a smaller size to create an average clearance. The tolerance grade 6 offers high precision and is used in applications such as wheel hub bearings or transmission shafts to ensure smooth movement. The numerical difference indicates that h6 has stricter control, while H7 is slightly looser, making production easier. Proper selection of fits can prevent issues like vibration, loosening, or thermal failure, which can affect the vehicle's lifespan. During maintenance, use plug gauges to check clearance, with standard values typically ranging from 0.02 to 0.10mm. Replace components if the clearance is too large to avoid premature failure.
