Hi Brian, I think I have now figured out how to get around my problem. I will be using a grinding disc of around 25mm diameter x 3mm thick which will be dressed to a 1.5 convex radius on it diameter. Thinking about it all I need to do is program the path of the centre of the 1.5 rad to produce the required shape using the X/Z axis without comp but have this tool controled by a second work offset that will be the distance between the centre of the 1.5 rad and the centre of the wheels spindle. This way if I need to dress the wheel I can reduce this second offset by half the amount I reduce the wheels diameter by. Then all the various programs will not need to be re done when I dress the wheel.