That magnetic rig is a great idea. Keeps the heat away from the magnet as well .

 

got one of these off of Amazon, they work great

 

Welding holes:
1. Don't try to weld holes > 1/4" without plug.
2. Go to a metal fab shop with a good sized clean flat scrap of 18 ga and a dozen donuts. Ask them (while waving bag of donuts near their nose, best before lunch) to use their turret punch to punch you a cup full of plugs 1/2", 3/4", 1".
3. Use step drill to redrill any odd sized or out of round holes to 1/2", 3/4" or 1".
4. View my "filling holes" gallery for pix on what to do next.

Use .023/.025 wire (preferably ESAB easy grind) and shielding gas.

If you have wires poking thru back, you are doing it wrong!

 

That's pretty much my rule also Ax... but the base metal is so thin from age/rust that you start with a 1/4 " hole and end up with 3/4"... the base blows away from the plug... I try to concentrate the heat on the thicker stuff and just wash over to the thinner... but it's tough....

only got two or three more bigger holes (with patches) to do and I'm done... let my body man make it all smooth and slick... fiberglass doesn't tend to blow out

j

 

You don't run beads when welding sheet metal, just 1/4" diameter round tacks. See my post yesterday in the "does this need patched?" topic.

 

I too, have a few porcupines in my closet. Nice tool Drew. Very clever work.

 

John,
I feel for you. I did mine several years ago. Who knew there could be so many danged holes in a firewall? And, like you, I created a porcupine on the inside of the firewall. I used a combination of filling holes using a copper backer, cutting plugs and welding them in, blowing holes, creating larger holes and then using copper backer, etc.
Here's a few pics;




I made the mistake of not filling in the main wire harness hole in the upper left corner...dang. After filling all the other holes I'm reluctant about poking holes for anything, I don;t even want to run a screw through the firewall. I poked a hole for the brake booster and throttle cable. Someday when I install a heater I think I'll run the heater hoses in through the side of the cab to keep the firewall nice and clean.

Bobby

 

When welding up a small hole without a filler plug, DO NOT start on the edge of the hole! Start your bead about 1/8" from the edge and run a bead from there in a spiral pattern to the center. A MIG welder is a short circuit machine, the end of the wire should be held in full contact with the metal and the torch supported at that height with the other hand before pulling the trigger. Wire sticking out on the rear results from pushing or dropping the torch towards the metal when the bead starts (or have the feed speed set too high), or having space between the metals at the joint larger than the wire diameter. If there is space, cut a new better fitting plug, or if I have a major portion of a patch already welded in before discovering the space, I'll cut a thin strip of metal , and slip it into the space edgewise so it is just proud of the surface and weld over it (or sometimes I'll use a piece of filler wire if it is a horizontal seam and the space is narrower than the wire diameter so the wire lays over and is supported over the gap). Always cut off any balling on the end of the wire before starting a weld on sheet. A ball on the end acts like a much larger diameter wire, adding excessive heat and resulting in burn thru. Don't be lazy or cheap and not change to a smaller wire when welding sheet!

 

thanks Drewski, and that is a great tool. Your posts on the Hamb really show all the ways you can use it. I will be making one.

 

thanks Ax, another excellent welding tip!