Get a W123 wheel bolt (You should have 20 of those!) and wrap some tape around the threads so you don't inadvertently score the inside of the aluminium tube whilst you are forming a new flared end.
Drop the bolt down the hole in your wooden vice - balance it on the corner of a work bench (or anything else that seems handy) - use a pin punch to help you whack it into place.
Please note the weedy little pin punch I used - you really don't need loads of weight here it is an ALUMINIUM tube not a steel one.