And, you will at some stage before reassembly need to lap in the flywheel so best do that now to remove any buildup along the edge of the key, until you see the clear outline of the key, then you can punch or drill more acurately and drilling with an old hand drill is safer, with a 1/16th drill bit and a hand drill you should be able to "swiss cheese" the key so it collapses especially if you have a fine punch to help it along.