Why setting a tick at 0.5 when you want to have one at 500 ?
Because it represents time, and I work with milliseconds and want labels to look as seconds. Anyway that's a different issue I'll try to solve next. This is what happens when you inherit code

PS: you can use QwtSlider::setScale( const QwtScaleDiv & )
Anyway, what would be the difference with the setScaleDraw I tried? Could you give an example of usage? Thanks