I have broken a couple of 400 vises. Far as carrier nuts go soak it wack it with a chasel and if it doesn't come loose easy stop !!! Drill three holes knock the drill section out, then turn it out. Cheaper and easyer to replace carrier nut. If you mount vise to work bench try an put on top of a leg so when your beating the s--- out of the drive you get a solid hit and no bounce. Don't forget to bolt work bench to wall so when you have a 6ft pipe on the end of your breaker bar the hole bench doesn't doesn't tip over on top of you.