Tips on Using a MIG Welder

Subject: MIG Welding question
From: "Mark A. Bunce"

My friend and I recently bought a Lincoln Electric welder (the Model 100), and we are busy learning how to make decent welds. So far we have been using the flux core wire for practice welds on fairly heavy gauge metal. We have the MIG welding kit which we plan to install soon so that we can practice MIG welding on some sheet metal scraps. My question is what gauge sheet metal is typically found on Triumphs? Does anyone with this type welder have any suggestions as to the welder settings we should try with sheet metal?

I have the same box and put on the mig attachment, it will weld so much easier. I use 25%CO2/75%Argon mix. I just spent about 25 hours replacing the right floor, rear quarter patch, inner, outer sills and scuttle repair. the settings very slightly, but C3 to D4 are a good start. Gas was set at 25-30 CFH. Migs are great. I may never use a buzz box again.

From: "W. Ray Gibbons"

Alex Levinson wrote regarding welding

On welding: Are those who say MIG welding is easy being disingenuous? Maybe a little. It is easy in comparison with other ways of welding I've tried, but not as easy as drawing a line with a magic marker, as one restoration text said. I agree, it is easy to burn through when butt welding 20 gauge sheet metal. If you teach yourself MIG welding by trial and error, there will be a lot of errors. If somebody who knows how stands beside you and tells you how to do it, it will get easier. I have sold a couple of welders (at no personal profit) to friends by proving they can weld a good bead the first time if I set up and show them how to do it. I suspect ,any have used the same trial and error, weld, grind, weld again method that I did.


The metal must be CLEAN. MIG does not work well on rusty or painted metal. The two pieces to be joined should be in contact, to equalize heating. The books say to leave a slight gap. That's OK with 1/8 in steel, but it only causes problems (IMHO) when welding sheet metal. Butt welding light sheet metal is challenging, I agree. To minimize burn through, have the best contact of the edges possible and--this is important--weld in short bursts so the puddle gels between trigger pulls. High buck welders have a stitch mode that does this automatically. Those affordable by hobbyists will do the same thing if you just keep pulling the trigger. If you try to butt weld a continuous seam on 20 ga without letting the puddle cool, the heat keeps increasing. You either have to be skillful enough to adjust arc length and travel speed (hard) or keep pausing (easier) to avoid burn through.

You will want to do this for other reasons, too. If you try a continuous weld, or even stitch welding without cooling periods, the panel will heat up and may warp. Not much problem on floor pans. On exterior panels that must not warp, weld 1/2 inch here, 1/2 inch far away, 1/2 inch in the middle, etc., with air or damp rag cooling between welds, until all those 1/2 inch segments are a continuous bead. When you can, use a flange (brit. Joddler) to make an offset on one panel, lay other panel on top, and avoid the hassles of butt welding. That gets MUCH easier.

More hints.

Heat and wire feed are only the most obvious adjustments. If the torch moves closer to the work, the heat increases. Ditto if the travel speed decreases. Strive to keep these constant, or change them only deliberately. If welding dissimilar thickness (e.g. floor pans to inner rocker), point the torch toward the thicker piece as necessary to heat both evenly, or zig-zag torch across the joint dwelling on the thicker piece. (If you do not have intimate contact between the parts, it will be exquisitely difficult to weld parts that are substantially different in thickness.) In general, think about heating of two pieces--for example, when welding a small patch into a panel, the patch will heat fast and the panel more slowly. Adjust torch angle and movement to compensate.

Big, huge, most important hint of all.

You can't do a good job of welding when you can't see what you're doing. Once in a blue moon you may want the hand held eye screen that comes with some cheap welders, but you should also buy a decent hinged helmet. Then save the glass (intended to protect 8 hr/day production welders) that comes in it for solar eclipses. Replace it with a gold coated glass (not sure of exact term, but welding store will know). You can adjust the hinges on the helmet so you can place the torch, using both hands if necessary, and nod your head to lower the shield (looks real professional). Trouble is, your eyes take a few seconds for the iris to adjust, so you cannot see the beginning of the arc. For really critical stuff, I beam a 600 watt bulb on the work so I can set up through the lens with the faceplate down; it also helps me to see things. If you cannot see the edges to be joined as well as you would like, draw a line along the intended weld with a soapstone marker. I also wonder at those pictures of guys free-handing a torch. You see them waving the torch around, but I bet that's not how they got the welds that are shown in close-up examples. I invested in a couple of machinists magnets and a piece of angle iron. When possible, I attach the magnets to the car, lay the angle iron across the magnets, and rest my hand on that. One can also rest the edge of the torch on the work at a slight angle, and the arc is about right. Or use the sign-painters method with a wooden stick and a rubber ball (a picture would be worth 1k words). Re welders. I have a Lincoln SP-100. It is pricier than the imports, but has continuous adjustment on both the wire feed and heat, a 3 yr warranty, and parts available at the corner welding store. Butt welds in 1/8 steel push this machine, but it can do anything on a Spridget. It is a good quality machine.

Ray Gibbons

To answer your questions on Lincoln Mig Welders:

The Weld Pack line is the retail Migs of Lincoln Electric. They are set up as flux core welders.

Mig Pac 10/15 and the SP 100T/170T are the 110V and 220V versions of the gas solid wire mig welders.

The mig pac is sold through automotive outlets.

The SP line is sold through the standard welding distributor.

To convert a weld pac you need a conversion kit which includes a regulator for the gas and some other gizmos. The low ball price on a weld pac is Home Depot.

"While I have no use for the flux wire, it works out free and maybe I'll use it someday to weld up something that doesn't need to look pretty. The gas is somewhat expensive to use if you are doing long welds."

All units can be converted to flux core wire. It is handy for welding outdoors. The heater in my garage will blow away the gas shield on my MIG PAC 15. The tips are $12.99 for a pack of ten. My whole Morris Minor restoration needed 2 tips.

All units come with a three year warrantee from Lincoln. The reason Lincoln gives this warrantee is the units are practically bullet proof. I have had my MIG PAC 15 in a busy body shop for the last year with no problems. It is used almost every day.

Where to buy is your choice. Lincoln is a commodity product line. With Home Depot bringing the price down it's hard not to go there. But....when was the last time Home Depot supported a car club? Gone to a auto flea market? Answered questions on rusty floor boards?


Curt Strohacker

And this from Ron Classen

The sheet metal thickness on your Triumph is probably about 20 gauge. I would not even consider using flux core wire on it. Use the 75%-25% CO2-Argon commonly available. Also, I'd use .023 wire as it works best on thin metal. Weld in short stitches so as to avoiud burn through, and warping. Base metal must be clean, as in ground down with a grinder. Rust, paint, and oil mess up Mig welds as does wind. When switching from flux core to gas shielded welding, remember to change the polarity on your welder as per owner's manual. Good luck.

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