What is the basic procedure for spot welding? I have several pieces I am replacing and need to spot weld?

Spot welding takes a spot welder. Are you talking about plug welding?

Unless you have a spot welder, or can rent one, you'll probably do just fine plug welding.

All you do is punch or drill holes in one of the flanges or pieces (3/8" will work) clamp the pieces together and fill in the holes with your welder. If you can't get a clamp on them, you can use sheet metal screws or cleco fasteners to hold them together.

Practice, practice, practice! Try pulling a few test pieces apart to make sure you are getting a good weld nugget. Make sure you are getting good weld penetration. Just because you've got a glob of weld bead on there doesn't mean you've fused the two pieces.

Spot weld - two pieces of sheet metal joined together by a weld. The spot welder tool clamps the metal together and welds them. Spot welds are used all over the body of a 914.

Plug weld- joining two pieces of sheet metal together but one piece of metal has a hole drilled in it and you use a mig welder to fill the hole with weld material. Also called a roset weld. Used all over 914s to repair sheet metal.

The plug hole size is determined by the thickness of the panels being welded and what kind of welder being used. Thinner material and/or a TIG welder will use a smaller hole, this will keep any warpage to a minimum. MIG and or thicker material will use slightly larger holes.

Thank you I get it now,,. Plug Welding..

The idea on a plug or rosette weld is to start the arc in the center of the hole and work circular out till you get to the edge of the top piece. The trick is to melt the bottom piece without blowing through. It is a combination of speed and heat. Tig can be more confined in applying the heat but mig is faster and a lot easier and will work with more contaminated metal easier than tig. Be sure and go far enough into the edge of the top piece to get a good fusion and so it doesn't have a void at the edge of the bead. A lot of times the bottom older piece is thinner from rust on it's backside and will not be easy to keep from blowing through. Sometimes if the metal is too thin you have to start and stop to keep the heat down and the pressure of the wire on the mig from pushing through the molten metal. Sometimes you are starting and stopping just to build the edge of a blown through hole back up and closed to fill the hole up. Not on rosettes but during normal welding: I try to start the arc and weld back over where I started, this usually looks better and fixes a cold non fused start or just one piece melted. Usually when you start the arc you start on good metal to keep from blowing through, then trail off to the thinner area or edge to keep the heat under control but coming back to the thicker area or just stop and let it cool. On cold metal if you can, always start at the edge of the metal and weld inward. If you go the other way the edge will burn away as you get nearer to it because of the heat buildup during the continous weld bead.

What about butt-welding the patch pieces in on rustorations?

Advantages, disadvantages, techniques, other thoughts??

It seems to me that I've seen ScottyB & McMark & maybe others here do this technique to patch in sheet metal where they're replacing cut-out rust areas, in order to keep the finished product smoother than with a lapped method of either spot or plug/rosette welding as described above.

While the lap where it won't be seen seems okay, it cannot give you as smooth a patch if you're patching in sail a sail/fender panel piece to repair a rusted area for example, & then you're dealing with more filler to make it up.

Butt welds are tough to do. If you get the area too hot you will burn the material and you end up with a hole. If done right a butt weld is the best way. It just depends on what and where you're welding. Fender flares should be butt welded. Floors can be spot welded.

To help from burning through on butt welds. One can put a sheet of brass behind the weld point held on by magnets (away from the weld point because magnets can affect the arc).

I will be tig welding my flares on when I get done with this crazy project for another car.

Best way to not burn through metal.

1. Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice Practice

2. Keep your weld moving

3. If you do burn through do not try to fill the hole right then, move to another spot.
Let it cool off then go back and fill it (if you try to fill it when it's hot it's going to get bigger and more nasty)

You can also make a spot weld by turning your welder up and blowing through both pieces and welding the jole up. It's tricky and takes practice but it makes a strong weld. Plug welding is easier.

I've also punched smaller holes and fusion welded with a TIG, but that takes a lot of tecnique, but you can make it look more like a true spot weld. Plug welding is easier.

Butt welding is the best way to put two exterior panels together, but it too take practice and patience. You also need a copper spoon to back up the seam, it helps mimimize blow through. I only run about a 1 to 1/2" bead at a time, and move around the seam so you never get one area too hot.

Go to a plumbing supply and buy a 12" piece of 1" diameter copper pipe. Hit pipe with hammer until flat on one end.

you guys are awsone with the precations and techniques.. I do have scrap material to pratice on..

Joe - our ROP here in town might have a night class at Orange HS or somewhere close to take a quick welding class too, & I think they're free. I was thinking of checking into that myself.