How are Gear Precision Grades Classified?

Gear precision grades serve to measure the accuracy of gear manufacturing, exerting a critical influence on the smoothness, accuracy, and load-bearing capacity of gear transmission systems. Within national standards, gear precision grades are typically classified according to the following aspects:

According to GB/T 10095 (Chinese Standard)

This standard specifies 13 precision grades for gears and gear pairs, ranging from Grade 0 to Grade 12. Precision decreases sequentially, with Grade 0 being the highest and Grade 12 the lowest.

1. Grade 0 - Grade 2: These high-precision grades are primarily employed in gear transmissions for precision instruments and aerospace applications demanding exceptional motion accuracy. For instance, high-precision gears are utilised in the transmission systems of astronomical telescopes to ensure flawless angular adjustments during observations.
2. Grade 3 - Grade 5: These represent higher precision grades, commonly employed in high-speed gears within automotive engines and transmission gears for CNC machine tools. For instance, timing gears in automotive engines require precise transmission at high rotational speeds to minimise power loss, necessitating gears within this precision range.
3. Grade 6 - Grade 9: This represents the commonly employed precision grade in general industry, suitable for gear transmissions in standard machine tools, metallurgical machinery, and universal reducers. Components such as the spindle box gears in ordinary machine tools and the reduction gearbox components in industrial production lines frequently utilise this precision grade.
4. Grade 10 - Grade 12: These constitute lower precision grades, employed in simpler machinery with less stringent accuracy requirements. Examples include non-critical transmission gears within agricultural machinery and construction equipment.

In accordance with ISO 1328 (International Standard)

Similar to GB/T 10095, ISO 1328 classifies gear precision into several grades, ranging from Grade 1 to Grade 13, with precision decreasing progressively. Its classification principles are also based on aspects such as the geometric accuracy, motion accuracy, operational smoothness accuracy, and contact accuracy of gears. This standard is widely recognised and applied internationally, facilitating quality comparisons and trade in gear products between different countries.

According to AGMA standards (American Gear Manufacturers Association standards)

Within AGMA standards, the classification of gear precision grades differs from the previous two. Its precision grade range generally spans from Grade 3 to Grade 15, with precision progressively increasing. This standard primarily emphasises the load-carrying capacity and reliability of gears under specific operating conditions. It is widely applied in North American mechanical manufacturing, particularly in heavy machinery, aerospace, and related sectors.

According to DIN Standards (German Industrial Standards)

DIN standards classify gear precision grades from 1 to 12, with Grade 1 being the highest precision and Grade 12 the lowest. This standard is extensively employed in mechanical engineering across Germany and several European nations to ensure high-quality and reliable gear transmission systems.

Gear precision grades are typically determined based on multiple evaluation metrics, including the tangential combined deviation, radial combined deviation, profile shape deviation, helix shape deviation, and tooth thickness deviation. These metrics reflect the manufacturing precision and quality level of gears from various perspectives.