This is a demo tutorial. While there is no step-by-step commentary available (yet), the live demo below is fully functional. Feel free to open it for full source code.
This demo shows how we can use events to automatically adjust ValueAxis maximum scale across data to set minimum value of its upper scale regardless of the actual value scales.
See the Pen Set the minimum upper scale of a ValueAxis by amCharts team (@amcharts) on CodePen.