Spot welding with a MIG

[egon]

I've seen it done, but can't figure it out for myself. Can anyone help me with this? I have a Lincoln Pro 175, with gas. I also have several types of wire on hand.

--Matt

 

[Captain Ron]

I've seen it done, but can't figure it out for myself. Can anyone help me with this? I have a Lincoln Pro 175, with gas. I also have several types of wire on hand.

--Matt

You might be confusing "spot welding" with "plug welds", which would make more sense with a MIG. It involves drilling a suitable sized hole in the "top" layer of material. Fill the hole with weld, being sure to get the base material first, and moving outwards to your top layer. Grind flush, or leave it unground as the situation calls for.

There may be other methods, but I'm not aware of them.


--ron

 

[egon]

Would that technique work with overlapped sheetmetal?

--Matt

 

[RichP]

Wait a minute, I've seen that kid pauly on american chopper do spot welds with a mig, just did some last nite when he was putting fins on those two rockets under the gas tank on that jet bike... I've also seen spots and tack welds on pimp my ride and overhauling... I've always done it with oxy/acl myself but that was many years ago. Mayhaps my terminology is off, I always considered spot and tack welds to be the same...

 

[Legacy]

I think you might be thinking of a plug weld that's when you have two pieces of metal one with an hole drilled, punched into it and you weld them together by filling the hole with weld, a tack is just that it's used to hold the pieces of metal together until you can weld them together.
Spot welding- there is no hole drilled you would also no be able to do a spot weld with mig.

I know if you go to the miller website they can explane it better.

 

[Captain Ron]

Would that technique work with overlapped sheetmetal?

--Matt

It does. The hole diameter can have a bearing on the amount of shrinkage you will experience.

--ron

 

[dmillion]

"Wait a minute, I've seen that kid pauly on american chopper do spot welds with a mig..."

What you've seen him do aren't spot welds, they're tack welds. My guess is that the original poster is also confusing spot welds with tack welds.

Spot welding is done with overlapping pieces of sheet metal and no filler metal. A quick, high current charge is passed through them and causes them to weld together.

 

[Beezil]

captain, legacy and dmil have it right.

you are thinking about plug welds.

true spot welding is a resistance weld, and does not use filler material or shielding gas, and cannot be performed with a mig welder.

 

[BrettM]

i guess it would be kinda like spot welding if you had overlapping metal and melted through the top one into the bottom.

 

[Beezil]

i guess it would be kinda like spot welding if you had overlapping metal and melted through the top one into the bottom.

its NOTHING like spot welding. Resistance(spot) welding is resistance welding, and gmaw, is gmaw. There really aren't ANY similarities.

if you wanna see what spot welding is, come down to my shop sometime, I'd be glad to give ya a tour.

 

[8Mud]

Spot weld, tack weld, the object is to hold two pieces of metal together. I´ve built a bunch of fork lift resistant (custom) warehouse doors. Drill a hole slightly smaller than 1/4". I work in MM, I usually use a 5MM or 5.5MM hole, use about the same spacing as a person would with pop rivets (every 4" depending on the stresses or load involved). I often skip a hole and come back to it, the object being to keep the heat down (spread out) as much as possible. I use 0.6mm or 0.8mm wire, doesn´t make much difference (straight C02 works just fine). I don´t use the stand off spot weld tip (that´s what it´s listed as). A cone tipped gas nozzle, helps in seeing the hole some. Close to or equal to a spot weld in strength. Technique and practice, will fill the hole, with a full melt, a spot weld (what it´s called in the book or is it a point weld?) timer can be helpfull, when learning. Flush grinding is to be avoided, if you have to flush grind, double the number of welds.
I´ve used a combination of spot welds (plug welds/point welds) and tack welds. Always being carefull, to spread it out and not overheat one spot. As strong or stronger than a, bead weld, after the heat issues, crush characteristics and such are figured in.
A nice trick is to keep a pump sprayer (like an empty window sprayer) full of water handy. Coat the area to be welded, with a light film of water. Doesn´t affect the welds a bit, helps keep temp.s down to avoid waves or boils in the sheet steel.

 

[Colorado_XJ]

Not that old man Niels Miller knew much about welding, but his company says:

"Spot Welding - Usually made on materials having some type of overlapping joint design. Can refer to resistance, MIG or TIG spot welding. Resistance spot welds are made from electrodes on both sides of the joint, while TIG and MIG spots are made from one side only."

...as can be found here:

http://www.millerwelds.com/education/dictionary.html

And AWS D1.3 even categorizes SMAW spot welding, used mostly in attaching steel deck lap joints to each other when thicknesses are under 3mm.

Egon, check out http://www.millerwelds.com/education/library.html or http://www.lincolnelectric.com/knowledge/ for starters. Also, straight Argon or a high-% Argon blend will work well as it carries less heat and gives you less spatter than straigh or high-% CO2..

-Rich

 

[Beezil]

okay, you guys got me....

I don't live fab through books, I am a metal manufacturer by trade.

if you ask for a spot weld in my industry, you won't be asked "what kind".

you'll get a resistance weld.

however, note taken, thanks.

 

[Colorado_XJ]

Beez, no offense meant. I hope none was taken. I live metal fab through books (had to for my degree) and have been doing it for more than a few years professionally. A spot weld in my trade is a weld through 2 lapped pieces of gauge metal using whatever process is available. Different sides of the same coin, you and I. On that note, next time I am in Chicago, I might hit you up for a tour of your shop. Always nice to check out another shop.

Egon, how goes the welding?

-Rich

 

[8Mud]

Most guys that work with metal are more than a bit anal, comes from having to fit two pieces of metal together, so the light doesn´t shine through. :wave:

 

[Beezil]

Beez, no offense meant. I hope none was taken. I live metal fab through books (had to for my degree) and have been doing it for more than a few years professionally. A spot weld in my trade is a weld through 2 lapped pieces of gauge metal using whatever process is available. Different sides of the same coin, you and I. On that note, next time I am in Chicago, I might hit you up for a tour of your shop. Always nice to check out another shop.

Egon, how goes the welding?

-Rich

offense???

you kidding me?

hell no.

you delivered 100-percent accurate info, I appreciated the correction.

you have an open invite.

good luck with your projects.

 

[Colorado_XJ]

offense???

you kidding me?

hell no.

you delivered 100-percent accurate info, I appreciated the correction.

you have an open invite.

good luck with your projects.

Mmm, tasty. I have a good friend at the Art Institute there getting his Master's....I have yet another reason to visit. Thanks for the luck! Right back atcha!

-Rich

 

[egon]

...Egon, how goes the welding?

-Rich

Apparently I'm good at opening can's of worms Anyway, thanks for the responses.

As for the welding. I'm repairing parts of the pass. side floor pan over the exhaust. one section is roigh over the frame rail so I wanted to "spot weld" the new piece of floor to the outer edge of the frame rail like its done in the factory. I wish i had a picture, but its the area in front and above the cat. Thanks again guys.

--Matt