Not sure if it is possible, but we'd need to know what chart options your are using as a start. Can you describe your x and y data series and what data source option you are using?
Data source is related records and a related table linked by customer_IDFK
X data series is a column on this ChartData table from for 'YearDate' (each single record is for a single year, ie, 31/03/2014, 31/03/2015 and so on)
Y data series is a column on this from the child table for 'cPercentFigure' which is a calculation of ChartData::FigureA/ChartData::FigureB.
The typical range for this averages around 60%, so I'd like the axis to be around this mark, ie 40-80, to ensure the line doesn't appear flat as it would do on a 0-100 chart.
Other data series which are on the same child table but appear on different charts are, for example 'cPercentFigure2' which would be ChartData::FigureA/ChartData::FigureC.
The typical range for this averages around 30%, so I'd like the axis to be around this mark, ie 0-40, to ensure the line doesn't appear flat as it would do on a 0-100 chart.
The above are a couple of examples and there are further calculations which appear in other ranges to which a more flexible axis would lend itself.
ChartData table setup, very rudimentary example:
CustomerID_FK YearDate FigureA FigureB FigureC cPercentFigure cPercentFigure2
1 31/03/2014 60 100 0.6
1 31/03/2015 30 100 0.3
Then I'm afraid that you've encountered yet another limitation to FileMaker Chart Objects.
I can't recommend as I haven't had the need to use one for this purpose.