Try using a 6 point socket or wrench to remove them. Torque converters do not use bolts and nuts. They are studs on the converter. If you grind them off then you just brought another converter. If you round off the nuts so they can't be removed with a wrench, then your best bet to save the converter is to use a hammer and chisel and try to split the nuts to get them off. Remember whenreplacing the nuts that they are lock nuts.