I know you've covered this topic before so apologies for going over old groung, but I want to repair a cast iron 'apron' from an old lathe. It has cracked - see pic - and am interested to know if this is possible to 'MIG'. It is about 4mm thick
You will need MIG Brazing wire; 'Copper Silicon' & NOT cheap!
Malcolm has attempted something similar, successfully, but is away on holiday at the moment.
Sorry I can't be of any more help but I've never really had hands-on experience with that type of job.
weldequip