Really timely for me. Just got done tearing down 60 industrial light fixtures and started on the 28 ballasts. I've been stockpiling transformers and will be starting on them tomorrow or Tuesday. Just now figured it up and have around 200 HEAVY transformers (not counting the little ones from computers). I was planning to use the Sawzall to cut one side of the copper coil and pound through the core. But I've got a wedge and small sledge I use to split wood (pretty much like your sledge) so I'll be trying that first to see how it goes. I've got a vice that weighs over 100 pounds so probably use that to hold them rather than two transformers.