I've been using something like this: http://www.harborfreight.com/6-inch-jaw-straight-sheet-metal-seamer-98728.html
Works good for folding the crimp over, then pressing good 'n flat, then fold again for a solid double crimp. The wide jaw allows pretty fast pressing.
Ken H>
Works good for folding the crimp over, then pressing good 'n flat, then fold again for a solid double crimp. The wide jaw allows pretty fast pressing.
Ken H>