MIG or TIG

[onuthin]

I just finished a class on MIG welding because people said MIG would better on the thin metal. I can do alright but I hear people say TIG is better. Most people I talk aren't working on a Z car. I would like to hear from those who have been there done that.

[JimmyZ]

While taking machine shop I got some welding instruction at the Vo-Tech. I'm not certified but have had many cert weldors say I would pass easily. I own a 200A/MIG, 300A/ TIG, Oxyfuel set and plasma cutter. All of these came to bear on the Z at one point or another.

TIG is too slow and filling holes with MIG is easier. Just use some .023 wire and Argon/Co2 with a decent MIG. Once knew a guy that TIG'ed all of his patches on a VW. Beautiful work, but the concours judges spotted some areas which had weld beads near the engine. (Points off for that) This was a shame because his patchwork was meticulous otherwise.

For autobody MIG seems to be best to me. Distortion is less with MIG unless you go to great pains to keep the heat down with TIG. (Using a .020 tungsten for instance) Fitup and cleanliness is more critical with TIG than MIG. To me, using a foot pedal beats the crap out of a silly torch mounted switch. Such a switch is almost a must when TIG'n parts on the car.

It is possible to TIG and end up with a weld that is perfectly flat on the front and back sides. There was need to cut an access hole for sandblasting in the top of my tank. (Picture below) Something critical like this could be MIG'ed but since it is a life threatening thing to have a gas leak I chose TIG.

[beandip]

I trailered my Z to a certified welder and he welded in my floor pan . He told me that he had trouble with his MIG and ended up using his TIG welder. I cannot weld a stitch so I cannot advise in any way . Just passing on what was what on my car . He did say that the thin metal was a factor . One thing I did screw in my floor with self tapping screws and they were about 5 inches apart all the way around . He filled the holes after pulling the screws as he went . Maybe this was a factor . I don't know . Gary Zed Findings floor pan .

[onuthin]

I have been practiceing on some used parts using the .023 with argon but I still blow holes in the thin metal.I try doing about 1/4 inch at a time and moveing down a little and repeating then coming back and adding another 1/4 inch but it burns thru after a couple of tries. Maybe I am trying to go to fast.I am turned down as low as I can go.Should the metal overlap or fit as close as possible and try to fill in the gap?

[a7dz]

I used MIG to weld in all the panels on this 70. As was talked about it tight places a MIG wins every time. The TIG requires a couple of extra cooling lines to keep the torch from doing melt down (more bulk in the welding area). Plus you control the heat with the hand or foot switch and feed the rod into the welding puddle with your other hand.

I use a wire made for welding sheet metal panels together. It is softer then the metals you are welding and grinds smooth faster. Called easy grind up here in the Northwest. Basically it has higher silicon content. Used C25 as the shielding gas and stitched the panels together.

I screwed the panels together every two inches and welded the holes up after the panels were welded in place.

[brushie1320022]

I have been a welder for 18 years. Depends on how close your gaps are in your metal.How thick. Tig welding is good on thin. But you have to weld a little and let it cool. It will warp because of the heat. Or you can just spot weld with the mig.

[a7dz]

I have been practiceing on some used parts using the .023 with argon but I still blow holes in the thin metal.I try doing about 1/4 inch at a time and moveing down a little and repeating then coming back and adding another 1/4 inch but it burns thru after a couple of tries. Maybe I am trying to go to fast.I am turned down as low as I can go.Should the metal overlap or fit as close as possible and try to fill in the gap?

You are asking questions quicker then I can type and post pictures.

Yes, it is easier to over lap the panels. The process I used was a crimped lap joint. I laid out the pieces then cut the panel out leaving an extra 5/8” of metal on the car. I then crimped that 5/8” lip so, the panels laid flat on each other. Temporary clamped the panels together and then screwed them in place to get the proper fit. This will take some time. The black line you see on the cut out picture is the weld line and edge of the crimp. Notice the panel left on the car is the one that gets the crimped lip and allows you to screw the panels together in the fitting process do not get in a hurry. Speed in this case causes a lot of extra work in the end. Note I left the gas door replacement out at this time and came back and fit it in later.

I bought the crimper from Easwood online. I used the 3" pair that is made out of vise grips.

[JimmyZ]

Here's a page I made for our type problems...

http://warbuddies.homestead.com/RestoHelp.html

If you have your machine on the "1" (lowest heat) setting and are using .023 wire and STILL blow holes then perhaps your wire feed rate is too slow. Maybe your travel rate is too slow. Try using a gold shade 9 lens on the "1" setting as this will let you see what is going on better.

Are the two pieces being joined as thick as the filler wire?? (.023) If they are thinner you will need to pulse the gun so that you can build some thickness. (At least on the thin areas) Just tap the trigger long enough to lay down a small glob of metal. See the link above for details.

Make sure that your wire feed is consistent. (Equip set up right, Rollers set right etc)

Here's a page I made which includes some welding tips. Autobody welding is not as critical therefore you can cheat a little and do things which would not pass otherwise. Use proper welding technique/practices for anything structural of course. Patching a fender or other cosmetic repairs is what I'm talking about.

Hope this helps.

Jim

PS Post a pic of the front of your machine. Maybe one of us has used one of these and can eye the settings for you.

[geezer]

JimmyZ has got it down! That is an excellent article, my hat is off to you. The only thing I could think of adding is pointing out the many years of practice it takes to become proficient in both welding and body/paint. I've been doing it for more than 40 years, both as a hobbiest and a few years professionaly, and made a lot of mistakes along the way. Then I realized there was more money in industrial painting. I have never regreted laying out the cash for good equipment. It's been put to good use. There is no better feeling than knowing you did it all yourself. As a kid I started out with oxy/acetelene using coat hangers as rods. My dad built our first arc welder out of florescent light ballasts. Things have come a long way since then. Butt welding with a MIG is just second nature now. Looking forward to reading the "more to come". Great job Jimmy.

[JimmyZ]

Thanks Ron:)

While I was out I thought about onuthin's welding experience. Onu... Have you welded on thin stuff before or did your training revolve around thicker material?

The reason I'm asking is because you may be used to weaving or some other pattern while laying a bead.

On thin stuff MIG is done with a leading angle with no weave. Just move in a straight line.

2c

Jim

[onuthin]

I started out on thicker metal just to get the basics down but I have been working with parts off my parts cars such as hoods and body panels.I took a plasma cutter and made a lot of straight cuts in it and have been trying to weld it back together. I get a lot of burn thru and warpage. I have a millermatic 135 with .023 wire and argon set on its lowest setting.I do have the wire feed slowed until I get more comfortable. I use a autodarkening helment.I don't see how anyone could weld without one. I tried but I was all over the place. Maybe if I speed it up it would help. I have had someone tell me to push not drag. I can't tell the difference.Any suggestions would be appreciated.

[JimmyZ]

Yes push. This keeps the heat moving ahead. Set the wire feed rate to a speed which sounds like bacon frying. Not a pop.pop ..pop but rather buwhaaaa. If you can feel the gun being pushed back by the wire contacting the material then you are going way too fast. I know this doesnt help a bit. Remember that fitup should be no further than the filler wire is wide ideally. You can get away with larger gaps but this is not ideal. The gap your plasma cutter is leaving is too wide. A good weldor could manipulate things to fill such a gap well but this takes finesse.

Try lap welds on thin sheet for starters. If you burn through on a lap weld then something is really wrong.

Another thing to try is the tack technique as mentioned on my webpage. Just try laying a series of tacks at opposite sides of the panel until all of the tacks close things in. Once again precise fitup is the key to making things easy here.

Remember that the slag the plasma cutter leaves behind is not ideal for joining. The metal's edge needs to be cleaned up. Use an air cutoof tool to straighten your cut and clean the edge at the same time.

I'd like to make some video of actual welding but finding a shade and shutter setting that lets all the detail through is tough.

I'll see about posting a vid tomorrow.

Jim