need a little advice on welding

[atichargr]

Okay what I am tring to do is weld a donor roof on my 1929 ford model A .... since it is sheet metal I would guess I need do spot weld all over the place thousands of them so I don't distort the roof or can I do some small welds just moving around? anyway I have a snap on welder I had the heat at 7 and the feed at 7 with the gas at 20 inches... it does have settings for spot, stitch and contiuous weld.. with spot with settings upto 4 seconds... I had it on contious weld and was able on practice sheet metal get it to get good penetration where if i bent the sheet metal back and forth it would break behind my spot welds... there is a lot of extra weld on top is this normal or is there a way to cut down on the extra metal and have a more of a flat spot weld? also sometimes the spots would look like "puter" very rough and pourus what causes that? any help on setting this welder up and getting a better weld would be appriciated.... I don't want to touch the welder to the car till my welds look a lot better! but I don't want to use a whole spool of wire and tank of argon co2 tring to get this right....

thanks,
simon

[gizzardgutz]

OK, while I'm not one of them, there are many that are more experienced MIG weldors. What will be needed and/or wanted is some more info. First, snap on welder needs to be expanded, what model etc. Next, in order to critique wels properly, photos are in order. have a little patience and someone will give you a better answer. Post the asked for info and you can get some serious help. sounds like an interesting project, too. Good luck and keep checking back. A MIG welder will get back to you.

[mn welder]

my metallurgy is a little rusty(get it) but some of the steel produced in that era had alot of iron it it makes it very difficult to weld

[David R]

I have used snap on welders, they work fine. Just practice until you are sure you have the hang of it before messing with that fine old car.

A whole spool of wire and a tank of argon isn't that much practice.

On some sheet of the same thickness, see if you can run 1" long beads. Forehand or push will help keep from burning through and will lay a flatter bead.

Got any pics?

David.

[Broccoli1]

Argon???

[David R]

Originally Posted by Broccoli1

Argon???

C/25 .... Oops.

Thank you
David

[atichargr]

I saw a good video on setting the welder up.. it said to use what would be a good heat setting then turn the feed all the way down pull the trigger and turn the feed up till you get a good sizzle, then check to see if the penitration is good ... adjust heat if needed then the feed to get the good sizzle.. which I did and the welds came out much better.. I also found if the two pieces are butted up together you need more heat than if there is a little gap between the pieces... is this true? I feel a lot more comfortable about welding now... so If I do 1/2 welds and cool with a wet rag right away and move from side to side the warpage should be minimal? or should I just use tack welds? I am using a ribbed roof I hope that it will help with keeping the warpage down... any more pointers would be great !!!!

thanks
simon

[ol' Stick Guy]

If you mean Pewter that could well be true. Leading cars was a very common body-work procedure pre 1970's you would spot braze, moving your tacks all over the place in order to avoid distortion
You want to do it similarily with your mig machine try running .024 wire as well if you can, after you finish a tack keep the gun there for a second to avoid oxygen entering the weld after the mig gas dissipates.
If you can check the "Puter" spots with a file if they are really soft and metallic you've got lead.
You say your machine has spot weld settings try 1/2 second for your weld time as low as you can handle for voltage and whatever wire-speed gives you a slight spray transfer you can also use naval jelly or a wire wheel to clean the parent and donor metals if the metal digs out with a wire wheel you've got Lead.

[tanglediver]

Originally Posted by antichargr

also sometimes the spots would look like "puter" very rough and pourus what causes that?

Very rough and porous is also called porosity, oddly enough! It happens to everyone sooner than later. Lead in the base metal is one possible cause. Another is any loss of shielding gas. Large amounts of contamination will do it, whether dirt, rust, paint, etc. Always prep the critical work by cleaning thoroughly. Best way to fix the situation is to practice with the machine on scrap until you get acceptable results.
Lead bodywork, I can't help you there! Good luck, though.