If you have to take that much of the weld bead out then you are better off grinding it out and starting over. I will grind down only when told to do so for aesthetics. We have a new employee who has been a "welder" for ever with tons of experience. Since he started any weld that a grinder can get to has been hit. It's sad to see pretty steel treated to poor workmanship. We all need to grind on steel from time to time but it should not be your job title!