Dressing Welds with All Metal and Epoxy Primer

[rustover]

One thing that Robert really helped me with last year was once I did my initial tacks to go ahead and grind those down before I place the next set. You don't want to grind them flush, but just down to where they almost are flat. To me this helps the next tack penetrate the same as the first one and it also helps reduce any pin holes by aiding in a continuous weld.

 

[Outlaw]

I do that, but I grind them flush. I will try leaving them just a little above the surface, then go back and grind the finished weld level. What kind of overlap do you do? Sometimes I get a pinhole cause I dont overlap enough.

 

[anotheridiot]

you see the discolored rings you know you got good heat. Too much heat and you curve the pieces together and give yourself a nice pocket for filler. I still say the only way you know if you are getting enough heat is to peek after the weld and see if both surfaces are equally glowing orange, otherwise its the flux for glue scenario.

 

[anotheridiot]

This polyester resin uses cream hardener. I don't think it is any less waterproof than resin with liquid hardener.

http://uschem.com/products/docs/TDSUSC58215_ALL_RESIN1.pdf

I dont know what that stuff is, or if it even applies to metal 2 metal claiming its waterproof. I just know if I am repairing a fiberglass tank in my shop and I use fiberglass resin with the liquid hardener, I know its going to hold water. I would not attempt that fix with a polyester bondo with cream hardener.

 

[crashtech]

I dont know what that stuff is, or if it even applies to metal 2 metal claiming its waterproof. I just know if I am repairing a fiberglass tank in my shop and I use fiberglass resin with the liquid hardener, I know its going to hold water. I would not attempt that fix with a polyester bondo with cream hardener.

What I failed to get across was the style of hardener has nothing to do with whether the final product is waterproof. More examples:

Liquid hardener products:
Fiberglass resin (waterproof)
Polyester primer (not waterproof)

Cream hardener products:
SMC resin (waterproof)
Polyester filler (not waterproof)

 

[anotheridiot]

well, metal 2 metal does not look or smell like bondo when you mix it and their manufacturer claims its waterproof but comparing a metal epoxy type filler to polyester primer is showing you are reaching.

If you dont want to use it, thats fine, maybe you should be telling the manufacturer they are wrong.

I wonder if you even consider urethane paint as waterproof. Isnt that the key to the whole deal, it cant get wet if the water never gets there.

 

[crashtech]

well, metal 2 metal does not look or smell like bondo when you mix it...

OK, it smells different. That's a clue that its resin technology is different than standard fillers, sure, but this has nothing to do with whether it is suitable for any given purpose.

...and their manufacturer claims its waterproof but comparing a metal epoxy type filler to polyester primer is showing you are reaching...

I haven't heard of this "metal epoxy type filler" that you say I'm comparing, all I am doing is providing examples that show either hardener type can be used to create waterproof OR non-waterproof products. I don't know what you mean when you say I am reaching, unless you mean I am reaching for the truth, if so, I agree.

...If you dont want to use it, thats fine, maybe you should be telling the manufacturer they are wrong...

I don't use it and don't recommend it, and trying to tell most manufacturers about your experience with their products is a waste of time. Besides, I have no dog in the fight, other than to advise that such fillers aren't necessary with properly done repairs.

I wonder if you even consider urethane paint as waterproof. Isnt that the key to the whole deal, it cant get wet if the water never gets there.

Everyone knows that coatings can get chipped, etc, and there are other ways for moisture to penetrate as well, like screw/rivet holes, keyholes, seams, etc. Epoxy on metal is the final line of metal protection that has been trusted by techs in the know for decades now, because it is proven to work. When epoxy is used properly, metal-filled body fillers are just not necessary, and are at the very least a bigger hassle because they are harder to sand.

 

[Outlaw]

The table inside your welder is generally for full pass welds, and typically with sheet metal you are welding one weld dot at a time or a limited pass. Higher heat setting is required to get full penetration welds and the "heat realized" is controlled by amount of time on the trigger pull. As far as feed rate, I set up machine first to get your full penetration weld and adjust feed rate faster (if needed) to prevent any blowout. If there's a higher amount of heat and not enough filler going in for said amount, the weld is going to melt something in it's way, hence a blowout. So yes, add more feed speed here.

As far as other comments I'd have to agree. Porosity in your welds is a weld problem, fix it in the weld stage. If it's that bad grind it out and re-weld. Yes we are here to learn and share methods with others, but continuing to perform a weld operation incorrectly gives you a bad weld subject to failure. Relying on a bandaid of fiberglass filler or all-metal over welds is not the correct way to get better at welding, it only makes you more likely to perform sub-standard work in the future. So for whatever process you use, if you're not getting the expected results, fix the issue at that stage. I highly recommend using test coupons to set up your welder's heat settings, feed speed, and also OPERATOR TECHNIQUE. Working on your good panels on your project car is not the time to find out these parameters. Then if you run into any issue on the car, you can eliminate/limit some of the trouble areas and better figure out what is happening..

Back to Marty's comment of controlling the heat with the trigger, I did a test weld about a year or so ago using .035 wire, and dialed in the settings for 3/16 thick steel (per the settings chart in the machine) bumped up the feed speed slightly, and ran some test welds in 19 gauge steel... The trigger pulls here are all of about 1/2 seconds or less. Note the test panel is clamped in free air to simulate butt welding on your car's panels. Note there are absolutely ZERO blowouts.

Front side....

Rear side....

Now this experiment is less about telling you to use setting XYZ on your machine and more about showing you that higher heat settings can be used to provide a full penetration weld, and can also be controlled by technique (minimal amount of trigger pull) It helps to get your welder problems figured out with a little bit of practice / experimentation, it will make you better at figuring out any issues that do pop up, and help to eliminate those crutches.....including fiberglass filler over welds. So practice to see what your machine is capable of, and fine tune your TECHNIQUE in the process. You'll start to see your efforts pay off in the results.

MP&C, once you have the seam spotted like your illustration, do you continue spotting between the spots? At some point in time, do you make a continious pass of spots to connect the weld?
Id really like to see more illustration on how the welded seam looks just before those welds are finally connected.

 

[MP&C]

Once you get to a point that the weld dots are about 1 to 2" apart, or where the panels are sufficiently anchored that they stay aligned together, here I will revert to overlapping rather than spotting between. The overlap helps to eliminate those pesky missed spots that show light through your joint. But to back up a step, weld dots get planished, ground to just above flush (helps maintain consistency in weld penetration over leaving excess weld to act as a heat sink) and then overlap the next set. Lather, rinse, repeat. Here's some pictures that help show the sequence and the results...

Cleaned up....

Other side.....

 

[Outlaw]

Awesome response! Can you explain "lather"? When you do the over laps, do you do them one at a time with cool time in between or continious without cooling?

 

[MP&C]

Shampoo instructions on the label: lather, rinse, repeat.. lol. Weld, planish, grind, weld, planish, grind, weld, planish, grind..


As far as tacking the panel, you would want to start your tacks at one end and work toward the other. I know many people will tell you to skip around to minimize heat buildup, and I have been one of those. But if you tack one end and then move to the opposite end, you run a greater risk that any panel misalignment may cause more material on one side than the other. Once things get all tacked up, this may result in a panel bulge on one side of the weld from any excess material. So tacking should always start from one end and working progressively to the other, to help to eliminate this by being able to align the panels together as you go. Now that the panel is tacked and weld dots are spaced about (2 or 3"), go back and planish each weld dot individually, to add a bit of stretch. At this point, I use a 3" cutoff wheel to grind down the dots to just above flush. This gets them out of the way for planishing the next sets of dots, and gets the material thickness fairly consistent over leaving excess weld proud, which would act as a heat sink to subsequent weld dots. And, by leaving them just above flush, you can do the final cleanup with a roloc sander all at once. by trying to grind things down to perfectly smooth after each, you run a greater risk of inadvertent sanding of the metal to the sides of the welds, which may thin and weaken the panel. So I hold off on this until the end. For your grinding disc, I prefer to use cutoff wheels about 1/16 thick. This gives a much smaller contact area than most any other method, so you will have less heat buildup from the grinding process.

 

[Outlaw]

So during the process, its never more than one weld at a time? Once you start the overlaps between the spot welds one to two inches apart, its still just one at a time with planish and grind in between.

 

[MX442]

Robert, you are the Professor. I have been following your tutorials for a few years, and they have helped me get the MIG sheet metal dialed in. I have also turned up my machine to about 16-14g settings.

A couple tips I can add:
Lights. I had a hard time seeing the puddle flow into the gap because it seems I was always welding in a shadow. I made some magnetic lights with outdoor LED floodlights like this:
http://www.amazon.com/Outdoor-Secur...=1464881415&sr=8-5&keywords=20+led+floodlight
This one is super bright. I can easily position them to where I can see what I'm welding. Small piece of 11g, weld a 1/4" bolt and wing nut to mount the light. Then super glue small rare earth magnets on the back:



I have also made one from a smaller 10w LED.


Clip the wire before each weld. It is time consuming, but really helps to establish an arc. If the ball is still on the end of the wire, it tends to spark, quit, and push back before establishing a good arc puddle.

After everything is tacked and planished back to normal, I can get away with about 1/4" beads without key-holes. By starting a bead in the open, and running it to overlap a previous bead, the bead acts a a heatsink. On weldingtipsandtricks.com, he refers to this as "backwelding". I get less pinholes and, 1/4 beads make it faster than dots. About 45 minutes per foot to tack, grind, planish, weld, grind planish.
Here's a front side vertical uphill weld I did the other day. 1/4" at a time.

Back side.

Anytime there is a little bit of distortion, I correct it before continuing.

Still not as perfect as MP&C, but it will do.

 

[MP&C]

So during the process, its never more than one weld at a time? Once you start the overlaps between the spot welds one to two inches apart, its still just one at a time with planish and grind in between.

If you look at the pictures of the lift gate on the previous page, you will see a grouping and sequence of events. So if it takes me 10 tacks to get a panel held in place, once planished and ground down, the next weld sequence is to overlap each of those last weld dots, following the same sequence of then planishing, then grinding. So you are doing more of an "assembly line process" than just one dot from start to finish. If it sounds monotonous, yep, sure is. But the focus is really on consistency. Same size weld dots, same overlap, etc, etc, and this should equate to consistency in amount of planishing required, and all things being equal, makes it easier keeping the distortion in check.

Keep in mind this is not the be all end all process of MIG welding sheet metal. But it is a process I've tweaked/developed over the years to help others have more success AND consistency in welding sheet metal. If it works for you, great! If something else works for you, great! If you've got a method that gives you better results, by all means use it. At the end of the day we should all be using TIG or O/A fusion welding for a better process. But the truth to it is most home hobbyists will be better suited to using the MIG, and my ramblings here are only an attempt to help them see better consistency in their results.. Which goes back to the original post of wanting to use all metal to fill pin holes or other defects. If we can get to a point of consistency in our process, we should see more consistency in the results, where in the remote instances we do run across an issue, it should be easier to work through a solution at the problem stage, and not have to rely on pin hole fixes just prior to epoxy primer..

 

[Outlaw]

MX442, thanks for contributing. I went thru the lighting issue as well as Harbor Freight auto darkening helmets. Then I got on to much better lighting during the process and invested in a Lincoln Helmet. Those both made monumental improvements to my welds.

 

[Outlaw]

MP&C. I agree, fusion or TIG is a better option, but I have not brought myself to start another learning curve with TIG. I did master fusion welding with a Henrob, not not the heat distortion that goes with it. Im still working on that. I can weld two cupons of 21 guage sheetmetal with no filler rod. But the coupons were small and I believe the heat leaves the small coupon before it distorts. When I move on to a larger piece of sheet metal, it warps.

 

[MP&C]

With a smaller coupon you are heating up the entire piece, and cooling the entire piece, so no appreciable differing forces. On a larger panel, the heat follows the weld line (HAZ) and the outer unaffected panel remains cooler. The hot tries to expand and shrinks after cooling, the outside lying area remains cool and tries to do nothing, the area between these two forces is where you'll see the wave of distortion.

 

[Marty Comstock]

Awesome response! Can you explain "lather"? When you do the over laps, do you do them one at a time with cool time in between or continious without cooling?

That's a reference to instructions on a shampoo bottle, meaning do it the same way you did it previously, and so on. It made me giggle, at least ;-)

 

[Outlaw]

Makes sense. Before I bought my Henrob, I watched a demo video. Guy did a small coupon and held it up and confirmed no warpage. When I got my Henrob, I repeated what I saw in the video. After a couple welds, I was fusing the metal (perfect fit) and small coupons. I was really happy. Then I moved on to bigger pieces of metal and warped like some beach.

 

[anotheridiot]

Its great that this is going the right way, I guess I would rather you fix your stuff and learn how to do it, get better at it only happens when you dont give up. I hope you can fix the welds, but if not and you dont have the different shop tools to replace the steel if you cannot grind and reweld anymore, you still try something that is "wrong" so you can finish your project and do it "right" the next time.