[MosquitoMoto]

Hey all, resident noob here.

Experimenting with lobster backing for the first time. Mild steel, 41mm OD and 1.6mm wall thickness (that's one sixteenth from memory...)

All steel cleaned and cleaned again, then wiped over with acetone. I'm using a 2% Lanthanated electrode sharpened to a point, 15cfm or so argon with a gas lens. 35 amps.

Okay, fit up isn't great. But why are my tacks so rubbish? Some of them seem bubbly almost like unpurged stainless.

I caught myself once or twice just shutting down the pedal (afraid of burn through) rather than backing off gradually, and I made a note of it and started backing off more gradually.

Is there something specifically wrong here, or do I simply need more practise at tacking steel?

And finally, I have some 1.6mm ER70S6 filler rod. Is this rod too thick or about right? Feels to me like I need a lot of heat to melt 1.6, and I might be better off with 1mm rod.

Any tips? Happy for any and all feedback.

Cheers,

Kym

[exnailpounder]

Hey Kym. Maybe you are just simply spending too much time in one spot. You don't need huge tacks for such thin metal. OR your arc length is too long and you're puddling a larger area than you need to. Also, without a good fitup, you burn away the edges further. That is apparent if you look at some of your smaller tacks(better fitup) compared to your larger ones. I submit this to you, I got back into TIG after a 15 year layoff so it was like starting all brand new but I did know the basics of welding to start with. Like you I searched for knowledge to help speed me along. I would get performance anxiety at practice time because I saw examples of some beautiful welds and wanted mine to look like those. You can drive yourself nuts with the minutae of the nuances of Tig. I took on the "just do it and get it done" mindframe and life got easier. Relax, have fun and you will get where you want to be.

[motox]

better fit up super tight arc quick blast

[MosquitoMoto]

Good tips exnail, thanks.

Yes, I tend to overthink things a bit, for sure. Agree with what you say regarding fit up. Set about actually welding this piece a moment ago and it was a disaster...a new helmet is on the shopping list because my welding went to hell. I just couldn't see! But that's a story for another post.

Thanks again.


Kym

[Coldman]

I think you might have your wire too vertical. Try laying it down and sliding a quick dab in when you establish a small weld pool and stop the arc faster.
1.6mm S6 wire is ideal. By the way if you grind or sand your low carbon steel to shiny, you don't need acetone. No benefit whatsoever.

[MosquitoMoto]

I think you might have your wire too vertical. Try laying it down and sliding a quick dab in when you establish a small weld pool and stop the arc faster.
1.6mm S6 wire is ideal. By the way if you grind or sand your low carbon steel to shiny, you don't need acetone. No benefit whatsoever.

Thanks Coldie.

Yeah, I was definitely bringing the wire in from a high angle when I was using wire - some of this was autogenous. Maybe I should calm down a bit with the acetone, I'm always super careful with cleanliness because as a newbie it's good to be able to say "Well as far as variables are concerned, at least I know it was clean!"

Totally lost it welding this piece after tacking. Think I have helmet woes, but will share more on this soon.


Kym

[Poland308]

Looks a lot like SS fussion work I've only done a little of that. But you should be able to get a good tack on something that thin with out wire if you had to.

[MosquitoMoto]

Looks a lot like SS fussion work I've only done a little of that. But you should be able to get a good tack on something that thin with out wire if you had to.

Yes, many of these tacks were without wire. Where the tack 'misbehaved' I used wire rather than hanging around too long and burning through. Still so much to learn!


Kym

[Poland308]

Really thin metal is not forgiving and you may alway get spots that seem to pop through. Think it has to do with the manufacturing process of the tube or pipe. Is it seamed or seamless tube?

[exnailpounder]

Good tips exnail, thanks.

Yes, I tend to overthink things a bit, for sure. Agree with what you say regarding fit up. Set about actually welding this piece a moment ago and it was a disaster...a new helmet is on the shopping list because my welding went to hell. I just couldn't see! But that's a story for another post.

Thanks again.


Kym

A good helmet is an absolute MUST. I bought a new helmet last fall and I don't know how I did it with that old piece of shit I was using. As far as overthinking things.....I am the KING of that realm so me telling you to lay back and have fun must mean I am getting old and slowing down. For all the advanced skills I have, I find myself utilizing the basics more than ever these days.

[MosquitoMoto]

Poland, it is seamed tube - Electronically Resistance Welded process.

Exnail, I still think I probably overthink things more than you do...but I'll have to think about it!


Kym

[Poland308]

You might hit some impurities around were the seam is that will sometimes give you holes.

[MosquitoMoto]

You might hit some impurities around were the seam is that will sometimes give you holes.

Yet another thing I've learned here - thanks!


Kym

[big gear head]

I spent about 9 1/2 years putting small tacks on jet engine turbine airfoils. I had to tack .010 thick inserts to an airfoil that was about .100 thick. I used .030 wire and I would strike an arc on the thick part and lay the wire on it. Then I would melt a ball of metal off of the wire and let it lay on the airfoil. I would then push the pedal down and let the ball melt into the airfoil and the insert. I do this a lot with other stuff that is thin. It will not work with aluminum, but it works on steel.

I think a smaller wire would help. This is going to be a hard part to weld because of how thin you have it cut on the inside of the curve. You are probably going to have to stitch it by putting a tack on it and let it cool, then put another tack overlapping the first one and let it cool.

[soutthpaw]

Don't use the pedal. There is ramp up and down time. If you have a button trigger on torch, try using that. Instant on at full set amps and then off (2T mode). Maybe a second or 2. Don't move the torch, keep it in one place. Fitup is everything with thin metal.

[rick9345]

When pie cutting a welded seam tube, Try to keep the seam on outside of curve/bend you are creating( widest part of the pie cut).
For thin(looks like it is for a headerpipe) fit up is the trick answer for the weld.
Amps and quick for a tack.

[exnailpounder]

Poland, it is seamed tube - Electronically Resistance Welded process.

Exnail, I still think I probably overthink things more than you do...but I'll have to think about it!


Kym

OTFLMAO!! Now thats some verbal judo!

[MosquitoMoto]

Poland, it is seamed tube - Electronically Resistance Welded process.

Exnail, I still think I probably overthink things more than you do...but I'll have to think about it!


Kym

OTFLMAO!! Now thats some verbal judo!

It's what I do...

Some good tips here, thanks all, especially rick and southpaw. Yes, I have a torch with switch and can control 2T up/downslope.

Another challenge is my huge size 26 torch. This is a tiny part...I feel like I'm a dentist using a freakin' crowbar!


Kym

[subwayrocket]

Kym , those tacks don't look crappy ...yeah maybe just a little big . I used 0.045 ER70 rod for that thin 2 stroke exhaust and the thin quarter panel too , just a very little touch for tacks . With zero clearance tight fit ups, I noticed i could push the puddle across the seam, making fusion tacks, have to do it quick...tried this after watching one of Jody's vids on this. Thin rod goes a long way on steels , especially when you're doing alum then go on to something steel .

[Oscar]

I saw no evidence of swirl/scratch marks from a coarse flap wheel/solid grinding disk. How exactly did you "clean" it? If you wire-wheeled it, all you did was shine-up the mill-scale on that mild steel. Millscale has to GO when you tig mild steel. It makes for a sluggish puddle and is just not good for a quality weld.

[MosquitoMoto]

I saw no evidence of swirl/scratch marks from a coarse flap wheel/solid grinding disk. How exactly did you "clean" it? If you wire-wheeled it, all you did was shine-up the mill-scale on that mild steel. Millscale has to GO when you tig mild steel. It makes for a sluggish puddle and is just not good for a quality weld.

Hey Oscar.

Tube is new. Cut it, ground the swarf off cut edges then cleaned all with lots of acetone. But I don't know the first thing about mill scale - tell me more!

Also, if I'm to flap disc this to clean, how will I achieve a smooth finish for final part pre-painting? Just use a real fine flap disc I guess?

Pardon my noob questions, still very new to this.

PS - part is tiny, OD of pipe is only 41mm, I think about one and three quarter inches in Americanese.


Kym

[Oscar]

http://weldingweb.com/showthread.php?76301-Millscale

millscale is dull, gray, charcoalish color on the surface of mild steel. Clean steel is bright/shiny/silvery. Start now of getting into the good habit of using a very coarse flap disk or hard grinding disk to remove millscale, and before you know it, your mind won't see it as work, and you will automatically do it without even thinking about it.

Remember, fine (>80 grit) flap disks do very little to REMOVE millscale. Millscale will polish nicely just like any steel, and this is not what you want because you will have worked to accomplish nothing with regards to bettering your tig welds. So don't be fooled. It needs to be a COARSE (<60 preferably IMO) to remove millscale without having to use all of your weight on your grinder. A hard disk makes this much easier once the edge is properly worn, just have to be careful to not dig into the metal too much if it is too thin.

[weldin mike 27]

No mill scale there, our tube that small is cold rolled and has a bright finish.

Mick

[MosquitoMoto]

No mill scale there, our tube that small is cold rolled and has a bright finish.

Mick

Cheers Mick.

Yeah, this is small tube and quite bright. ERW seam. My concern with stuff like this is that if I do indeed have to flap disc it or whatever, how will I ever achieve a smooth finish pre-paint for exhaust tubes?


Kym

[weldin mike 27]

If you do have to sand, using a nice fine grade of disc and a light touch and you won't see any marks, unless you are painting for a mega dollar show bike

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