The only specialist tool I use when making patches is an edge joggler.
Hardwood offcuts, angle iron, old brake discs, sockets all serve as formers, with my vice or G clamps applying the force. I tend to reach for any hammer if I want one, there's usually a bit of scrap timber directing the blow anyway. Pliers are great for forming flanges accurately by just easing the bend gradually along the fold line. If the flange is on a curved edge, bend intermittently, to leave shallow peaks that can be shrunk by hammering the pointy "summit" against one of those improvised formers.
I do have a plumber's bossing mallet that's handy for stretching and a club hammer makes a great anvil/stake/ dolly as you can stand on the handle to keep it steady.
Remember steel work hardens, so get the maximum effect from your efforts. Constantly smacking it between two hard surfaces where it has nowhere to go hardens it more than it shapes it.
Exactly that, it's not how much the tool cost but the tool using it. I've made do with a selection of basic hammers and the odd of cut of wood over the years.
I repaired the below using nothing more than a claw hammer, some wood, a section of basic pein hammers (all with burn wooden handles from welding) and the side of a club hammer used as a dolly.
Edited by 1984mini25, 02 January 2016 - 03:42 PM.