Welding really, realy thin sheet metal

[Jeff T.]

Before I shut down the pc tonight I thought I would ask for a bit of welding advice.

I have slowly been working to fix a major rust hole in the lower front corner of my 62 Lark Hardtop's right door. I used patch panels cut from a half scrapped rear door off of a 63 station wagon. The hardtop door was not in the best of shape to start and in some places I had to set my welder to the lowest setting because of the thinness of the metal... there were times when the metal heated up it would melt like newpaper would burn when lit by a lighter. I would eventually get things tacked then welded but I ended up spending a lot of time building up metal that just vanished. I would end with solid welds but the fill wire would glop up because of low heat or I had the feed set wrong.

Any advice on how not to melt away thin steel and piling up fill metal that takes time to grind away. I do not remotely claim to be an expert but a lifelong learner with a work in progress.

thanks,

Jeff T.

[Bob Andrews]

If it's that thin- thinner than other areas- that means you haven't cut out enough rusted metal. Cut back until you get clean, solid metal and build from there. If you don't those areas thinned by deterioration will bite you in the a** sometime after the paint work is done

[52 Ragtop]

If the metal is that thin, you need to cut it back far enough to get to solid metal. Use weld through primer, and be sure to coat the inside of the repair with something, or it will continue to rot away.
Another way is to buy some panel bond, 3M has some (8115)and kent industries has some (4050) Using the adheasives, will make a solid bond without any gaps and sealing the metal together.

Jim

[Mike Van Veghten]

Doing some sheet welding last weekend.
After MUCH experimentation, I found that with the power very low (15 on my Miller) and the wire speed up (about 30) it worked pretty well.
With the wire speed lower....I was burning holes in "good" metal. As I was turning the dials...I just happened on the low power/high wire speed (sorta high) worked well. You might want to try the lowest power and a mid speed...see what happens on a GOOD piece of material. Experiment a little on good material, so that you JUST get a bead on the back side (good burn thru) of the weld.
Then as Bob says, verify you're welding full thickness material, not partially rusted.

Mike

[wolfie]

Once you get to solid metal how about a heat sink behind the weld? I welded up several holes in the top rail of a brand X truck bed with this method and it worked well. Steve

[sweetolbob]

Jeff

Steve beat me to the backer suggestion, but remember that the easiest weld to run is horizontal, so removing the panel and laying it down makes it easier. If you still burn through you can, instead of a butt weld bend a shallow flange in the repair panel and weld. That gives you two layers. I have a set of pliers that will make a shallow flange, this helps with less than pristine metal. Another "cheat" is to use a copper backer at the joint to adsorb heat. The weld will not stick to the copper and you can just flatten a piece of copper pipe to use.

Mike V's suggestion should also help. A quick "shot" with the Mig at higher feed can help. But just one last comment. I've learned by experience that in most cases it's better to run a little higher on both Feed and Amps than you would expect. Just use real short bursts with the trigger.

One of the best investments I ever made was to buy a Century MIG 160Amp welder years ago with infinite adjustment for both feed and amps. It's amazing how a small adjustment can make a big difference.

As you know practice will make you better.

Bob

[Jeff T.]

In retrospect, I should have sliced more from the lower right corner but I cut a 9X6 chunk from the outer face, removed the the seams in the corner and half of the door bottom... at the time I thought it was enough

Thanks for the copper heat sink idea. I discovered a bunch of holes yesterday between the inner quarter and the wheelwell so after I finish the right side floor its on to the wheelwell...

Keep the advice coming It helps me do a better job down the road

Jeff T.

[fatboylust]

I have no personal experience with this product, but found the link in an archive thread from this forum. http://www.muggyweld.com/super1.html

[3x2stude]

Welding sheet metal can be frustrating on flat panels. As all others have said it is important to have good metaal, clean both sides. regardless of how you fit the joint, butt or offset lap there is one technique that will help with distorsion. It is called back stepping the weld. You certainly don't want to burn the weld non-stop from on end to the other. Most people are aware that a skip weld will reduce dwarping but its method is important. Lets say you are going to weld the seam from left to right. You would then start about 1 1/2" into the panel and start the weld pulling it to the left. The next weld would be started at about 4 1/2" in and be welded again to the left for 1 1/2" leaving about 1 1/2" between the welds. Repeat the process all the way across the panel. Let each weld cool befoer the next is made. The next step is to do the in-between welds. Dress ant start / stop goober before you start with a grinder. Repeat the process just the same. What this does is put all the distorsion equal across the panel and not chased all to one end for a disasterous buckle. Also as all the other have said is practice on that old Camaro panel and then do the magic on the Stude!


Jon Kammer

[prager]

Use the thinnest wire you can get...23 or .24.. anylarger will take too much heat to arc and in turn burn through your sheet metal right away. I have a Miller 251 at work, loaded with .35.. guys come in and ask to me to weld thin sheet metal etc, and I'm turning them away. A good hobby type 100 amp or smaller welder with the thin wire is more than enough for body work.

[Dan Timberlake]

I'm guessing you're using a MIG welder. Flux core or gas? What polarity ? On my older Lincoln the flux core setting is the one for greatest heating of base metal for best cleaning and "penetration." Good for repairs on snowplows etc, less good or even bad for thin stuff. Some folks report running flux core "reversed" with better results on sheet metal. I have not tried it, yet, myself.

[Kdancy]

above - very good points--
What type and brand of welder are you using? No two welders weld exactly alike but if we know what you are using maybe one of us has the same type equipment.
My miller 210mig that uses 220 current, has a placard inside the door opening that gives you a very good starting point on settings depending on the metal thickness, wire size, type of metal, gas or no gas. I always use gas, 75/25 mix and .023 wire.
I have found that to be very close and then I make adjustments from there on speed, then heat if needed. I have also found that things will change from time to time depending on temperature and electric current actually coming into the shop, as that too changes based on area demand.
I sometimes use a brass plate to hold against the back side while welding as it is very helpful when welding really thinned out metal as the weld won't stick to the brass. Several companies sell brass paddles just for this.

[stuuder]

with todays technology I know a lot of body shops are using panel bond, no rust, no heat, no warps...........

http://solutions.3m.com/wps/portal/3M/en_US/3MAutomotive/Aftermarket/Products/Product-Catalog/?PC_7_RJH9U5230GE3E02LECFTDQCEK3_nid=2VC2PJZ33GbeNGQGZXQ0C5gl

http://www.pliogripbyvalvoline.com/panel_bonding.html

[oldguy]

A few of years ago I read about a new welding wire for MIG's. IIRC it was .30 diameter so it would run in a regular machine, but it was hollow (no flux core, just hollow). Result was a wire = to .20 with a very very low melting point. Touted as ideal for thin body panels. Supposed to be "available soon", then I heard Lincoln bought the rights to it. As yet, I've never found it for sale. Always thought it would be ideal for panel repair. Anyone else heard of this?

[jclary]

Unless I missed it somewhere, no one has mentioned the welder "Duty Cycle." Most of us with hobby grade welders need to pay attention to the duty cycle rating of the welder we are using. The duty cycle determines how long you can weld VS the time you need to let the welder rest and cool in order to maintain efficiency.