As others said, 1/4 will never cut, just rubs. Needs to be <= 1/32. I use a Sharpie to "paint" the very corner of the wheel. Pretty easy to see how much is left while undercutting the side, especially on a white wheel.
I've done to 1.5 degree with a slide dresser or a radius dresser. That sharp edge wears quickly, then more of the side starts to rub. Difficult to redress.