QChart Y Axis Min/Max settings do not respond to small numbers

QChart Y axis do not change when setting min & max values to numbers < 1.0E-12

I add one or more series to X& Y QValueAxis & use

axisY->setMin(_lowValue);
axisY->setMax(_highValue);

as long as _highValue > _lowValue and the _lowValue > 1.0E-12

the chart responds as expected.

if either the setMin() or setMax() uses anything <  1.0E-12, the chart no longer responds.

To confirm that the chart is really getting these values, I use the 

axisY->Min() & axisY->Max() gets and the values are present.

ie;

axisY->setMin(1.0E-12);
axisY->setMax(1.0E-11);

works fine. If I use :

axisY->setMin(1.0E-14);
axisY->setMax(1.0E-13);

the QChart does not respond.