arc welder as spot welder?

[sdowney717]

is there a way to use my AC welder as a spot welder for some sheet metal? It is a 240volt standard type model.

[Bill Thompson]

If you have ever seen my arc welding efforts on sheet metal (at least thinner 16 gauge), you'd probably say that all of it was "spot welding". ;-)
Definately needs steadier hand and better technique than my farm yard welding skills. Pipefitter or some of the other pros will probably offer some real advice. Most of the sheet metal welding that I have seen (really high quality work anyway) has been gas welded with small tips.

[Bill Huson]

Once upon a time many moons ago I had a cheap attachment thinger that made spot welds using juice from my 225 amp stick welder. I seem to recall it used a carbon rod like the rods in a twin rod gizmo one would use to toss a flame using juice from a stick welder. Probably got it from J C Whitney, purveyor of all things cheap & flimsy.

[Lewisboats]

Drill small holes where you want the spots, clamp and hit it with the stick on real lo amps...buzz it with a grinder and buffing wheel to finish.

[ABfish]

Use the smallest rod you can get, either 3/32 or 1/16 inch. With the smaller rods, you will introduce less heat into the sheet metal and reduce warping. Use a medium penetration rod like a 6013 to reduce the possibility of burn-through. Do not use a 6011 or other high penetration rod.

I haven't seen anyone gas-welding since I took a welding class 25 years ago, but if you have a torch and a little time to experiment, that is also an option. When I was a kid, I remember watching a mechanic repair an exhaust system with an oxy-acetylene torch, using a coat hanger as a filler rod.

[pipefitter]

The spot welders I always used were dedicated stationary machines. Try here.
http://www.eastwoodco.com/jump.jsp?itemID=1227&itemType=PRODUCT

[chainyank]

Drill small holes where you want the spots, clamp and hit it with the stick on real lo amps...buzz it with a grinder and buffing wheel to finish.


This is what I have always done in a pinch, works well, and you can make a nice neat weld... NMHO

[seo]

I think the info above about JC Whitney & Eastwood is good-both those companies are purveyors to motorheads with their sheetmetal issues, fantasies, etc. I think that spot welding machines might be usually DC machines, and an AC machine might not work as well even if you have a spot welder attachment.
I also like the idea of drilling small holes and welding through them. That makes perfect sense to me.
It is certainly possible to weld with Oxy acetylene and a steel stick. A clothes hanger isn't a new trick. I've had reasonable luck with that, and would experiment first with the flux, and make sure that you get all the paint off the rod. In my limited experience the steel rods you buy at the brazing rod store are better than coat hangers.
Which raises the question of whether maybe brazing your sheet metal parts might not be better, given the situation. I've found brass rod to be more forgiving than steel rod, because the melting temperature of the rod is lower than that of the piece you're working on.
I guess the point is that a spot welder is a production fabrication machine, and there are other ways to achieve the same end result without needing that specific gizmo. Even soldering might be an option, given the service. Some time ago I watched some roof guys solder up a standing seam galvanized steel roof, using soldering irons heated with a propane torch. Lovely job, simplest possible tools.

[pipefitter]

Using a drilled hole is what we call a button weld. It's somewhat hard to do with a stick at the size of a spot weld. The reason for spot weld machines is speed and lack of distortion on light gauge steel and it clamps the pieces together all in one motion. It is especially handy when working with galvanized so you don't have to disturb the plating, nor distress the surface with grinders etc.

[seo]

So with a "button weld" as you call it, do you drill through both sheets of steel, or just through one?

[Lewisboats]

Just through one...then you are welding the edges of the hole to the bottom piece and filling it in.

[sean.b]

Hi what thickness is the metal that you wish to join and if it is on a boat can you tell us what you are doing this might help to get a clear picture.Cheers Sean