Difference between actual gear ratio and nominal gear ratio

Questions: Difference between actual gear ratio and nominal gear ratio

Answers: 

There are two types of gear ratios for Varitron Geared Motors: nominal gear ratio and actual gear ratio. Nominal gear ratios are represented using integers such as 1/5, 1/10, 1/15, and so forth, and are unified among each model. Actual gear ratios are figures unique to each model.

This is usually cause due to Gear Profile Shifted when designing helical gears, this is important to meet the center distance and to maximus the gear withstand torque.

For example, the GH22 0.2kW model has nominal gear ratio of 1/30 and actual gear ratio of 1/31.9. (Some models or makers might have the same nominal gear ratio and actual gear ratio.)