I shoot for almost no significant gap when making patch / filler panels...Maybe .010" all around... You just don't want the filler piece to be tight in the hole when "cold", since it can bind/distort when it expands when you start welding on it...

You also want to dial in your heat and wire feed such that your weld bead lays out almost flat, as opposed to being a big "log" of welding wire bead that is sitting way up high that you will have to grind a lot down. As GW already said you don't want to be trying to hammer and dolly to manipulate weld sites.

To avoid distortion make many small tacks to get things in position, carefully grind those tacks flush, then clean all of it and prepare for the actual welding...Do about an inch of bead length at a time, let it cool, keep a wet rag nearby to help cool off the nearby areas...

.023" wire all the way... That one change will probably be the biggest help... You also probably only need between 12-15 CFH on your shielding gas. You only need enough to create the shielding environment, no more than that.

Thanx for all the input guys!!!!! I have a LOOOONG road ahead of me so I really need to get this right.

I couldn't agree more. I've tried both Mig and Tig many times and the Tig is simply the best for this. Cooling the tacks with the air hose helps greatly as well.

Mike

Everything that has been sad here about purity, tight caps and useing tig is 100% true.
But if you still do burn it through with mig, this is the tool/ a way that will rescue you.

http://www.harborfreight.com/media/c...image_7944.jpg

Put this flatly and tightly behind your coming big cap weld and tack. Maeby little longer that normal, you need more stuff cos bigger cap. You just have to practice how to use it.
If and when it burn through molten weld will be flatten in the surface of the copper and sence mig welds wount stick on copper, it will spread around and stick arounding sheetmetal edges and you will be saved. And sence copper is good sucking heat it will cool the weld after as well.

You can weld up big caps and grind them flat after.

Or you can use a piece of aluminium flat or block for withdrawing heat from welds. They work also. If you have a straight edge block of Al, you can use it as welding helpper for 90' angle and heat remover.

Again, this is not the way you want to do it, put its the way you can save stuff when you screw them up.

As myself, I havent never ever needed to use this.:lol: I have heard all this from a friend ;) ,have not :lol: :lol:

For cooling welds, I have use this kind of simple but effective device:
Take a normal (coke) bottle, 0.5 litre is just fine.
Take the cap and drill a hole on the top of it, just little pit smaller that the hole in the bottle it self.
Then put a piece of fabric, welding blanket or something that is not likely to set on fire or melt instantly when comes contacting hot weld.
Fill the bottle with cold water and screw the modified cap on. Now you got a welding cooler ready.

Put a tack and with other hand press the bottle (cap first) on that tack and squeeze a bit, cool water will cooled to spot and no excess water all over workplace and yourself.

[QUOTE=ironworks;326384]These pictures from Tyler's 50/50 car might give you some idea of how it is done. The fit is CRUCIAL for Tig welding. You cannot get great results with a Mig. You can do OK, but not what you can with a Tig. The fit up is super important. Then you need an air hose and and lots of patience.

Practice, Practice, Practice, Practice..... You can always improve


What rod are you guys using for this ?

Thanks,
Brian

[QUOTE=speedfreak;330743]I'm learning that you have to get the metal as tight as possible. I found this out real fast. You try and fill gaps with the mig and you always wind up with small pin holes from a hot edge. I'm on my third set of wheel house's I better learn this fast its getting expensive! I have a new tig but I'm not even thinking of pulling this out until I learn how to get this mig thing figured out....

I've made these for years - but I use copper plate (thin) which you can just cut or bend to your need -- or I smash the end of a piece of copper pipe. Not having a handle that is at a preset angle and length, is handier for me than a tool like this. Works the same either way -- there's just handier "versions" getting the same job done.

Once you really have a handle on welding you find you don't need this kind of stuff 98% of the time I can buzz a hole up without this aid... but these kinds of tools (homemade or otherwise)... can help a guy out in a hurry.

If you're by yourself -- a small piece of copper just snipped off a sheet - can be held in place using a magnet spanning the copper (since copper isn't magnetic) as a backer... Finding something - or someone - to hold this tool takes more time than my quickie fix. LOL That has worked for me if I'm trying to slick a firewall where your arms won't quite get there from here. :_paranoid and the area you're plugging is too small to make a fill piece.

GregWeld, your right on the money.
This is a handy tool if you weld some thin or damaged material.
Sure it can be duss hole close but this do it faster and most important that this draw a lot of heat away.

I also use a piece of coppertubing, 1/2" hammered the other end flat and have bendet to fit what every I do with it.

I have seen somebody to use those hold-down toggle clamps combined with a piece of copper tin for one mans working.

Again, I'm not a pro just a everyday welder how wants to get better doing it.

[QUOTE=DOOM;331644]Honestly, Trying to get it figured out with a MIG is totally different then a TIG. If you scribe tight light to trim and fit you can tack it up with the MIG. But learning how to weld sheetmetal is like trying to learn how to ride a bicycle when you want to ride a unicycyle. Just start now with the tig on 20amps and maybe buy some MIG wire to not build up your welds to much while your learning. The TIG welders out number MIG welders 5-2 in my shop and all my MIG welders are 110 volt except 1. I have 1 220 volt MIG.

Spend your time learning how to trim and fit sheetmetal very tight. Then learn to tack with the TIG.

Learn to cut gap and fit like this
http://i616.photobucket.com/albums/t...ary2011010.jpg
http://i616.photobucket.com/albums/t...ary2011014.jpg
http://i616.photobucket.com/albums/t...ary2011015.jpg