A 4 inch angle grinder will cut deep only up to half the disc’s diameter, that is, 2 inches. This means that it will only make smaller cuts. Any disc will cut only up to half it’s diameter, and if you want to have deeper cuts, then you will have to use larger angle grinders. A 4 inch angle grinder will not be as efficient in working with big projects, as a 7 inch or 9 inch angle grinder.