ok, this explains it:
http://msdn.microsoft.com/en-us/library/dd456730(VS.100).aspx
In the Chart control for Windows Forms, you can give the chart viewer the flexibility to zoom and scroll the data view by enabling cursors and selections. To do this, use the CursorX and CursorY properties.
You can enable cursors, zooming, and scrolling for the X or Y axes, or both. To enable the cursor in the data view, set the IsUserEnabled property to True. To enable data view selection, use the IsUserSelectionEnabled property to True.
Zooming and Scrolling
By default, zooming and scrolling are enabled when you enable data view selection. Use the ScaleView and ScrollBar properties in the chart area's X or Y axis to adjust the look and feel of the scroll bar when it is shown.
To disable zooming, use the Zoomable property found in the respective axis' ScaleView object. To disable scrolling, use the Enabled property found in the respective axis' ScrollBar object.