Is it spinning without turning the crank? If so it's stripped. You can wedge a flat screwdriver behind the magnet and twist while turning the nut. You can use a 7mm or 1/4" die to fix the crank. 7mm nuts are not that common however.
Is it spinning without turning the crank? If so it's stripped. You can wedge a flat screwdriver behind the magnet and twist while turning the nut. You can use a 7mm or 1/4" die to fix the crank. 7mm nuts are not that common however.