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  #1  
Old 07-31-2019, 06:05 AM
mabbo mabbo is offline
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Default Tig welding, and planishing the weld. Im struggling a little.

Hi,

Im confident using my mig to weld in my repairs and I get pretty good results, but I really want to tig. I have a tig and I use it very rarely but when I do I fusion weld as thats all I have been taught.

I decided to tig a repair into a project Im working on at the min. I hoped to fusion weld it but I trimmed the panel a little short and there was a small gap. Too small to mig, so I decided Id tack it in place with the mig as I was out of Argon for the tig, get a new bottle of argon and tig it in with some filler rod.

I welded at around 35-40 amps. I built the puddle on the top of the mig tack then welded to the next tack, about an inch at a time, adding 1mm filler rod. I blew a couple of holes but considering I havent hardly ever tig welded with rod, I was fairly happy with it.

I ran the file over it and every where there was a mig tack its high. Iv been hammering the weld with a planishing hammer and a dolly the closest shape to the panel I can find behind the weld but I cant seem to get it nice at all.

This is my process so far:

1) Trimmed my donor panel and quarter panel close enough to scribe:


2) Tacked it in with the mig, ground the tops off the tacks and hammered them back into shape:


3) Welded it in about an inch at a time, from tack to tack. Didnt planish as I went. Quite a lot of material:


4) Quick block with 80 grit to show the highs and lows:


5) After struggling on around the first 10 inches of the panel for around an hour I dont seem to be getting anywhere fast. I put a little more die on it and filed it to show highs/lows of how it is now:


I just cant seem to get it nice. Iv tried hammering on just the weld with a planishing hammer and dolly, then removed the excess weld when it was proud... Then I tried hammering on the lows on dolly with a planishing hammer, hammering on the highs with a planishing hammer off dolly, and with my slapper with the dolly on the lows. None of this worked very well and Im reluctant to go at it too much as Im worried about changing the shape too much instead of just stretching the shrinkage. Iv also tried hammering the lows out from behind the panel with a crowned hammer into a shot bag when I started to loose patience.


Am I getting it completely wrong or do I need to just be more patient?

Any tips / advice / criticism welcome.

Cheers, Neil
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Last edited by mabbo; 07-31-2019 at 06:07 AM.
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  #2  
Old 07-31-2019, 08:06 AM
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Steve Hamilton Steve Hamilton is offline
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Neil
Looks like you are making progress, planishing and metal finishing is not a fast process. One to one and a half hours per foot of weld is not uncommon. Make sure that the weld bead is grind down to the thickness of the base metal before planishing. If the bead is thicker as you hammer on dolly the excess metal will create more area, which creates a high or low spot, as the metal has to go somewhere.
I try to get the fit up of the joint as tight as possible before tack welding, filling a gap requires slower weld speed and more filler, which both lead to more shrink in the heat effected area (the blue colored zone).
Some tips that might help with future welds.
All tacks and beads need to be ground to the same thickness as the sheet before planishing so the stretching is even along the weld zone.
Planishing can be done a little at a time to help keep the shrinkage under control. Weld an inch, grind off excess bead and planishing. Then weld another inch and repeat.
After tack welding if there is gap in the joint between tacks hammer on dolly the edges of the sheets and they will stretch out and fill the gap. Donít hit the tacks as that will spread the sheets and increase the gap.
You may want to spend some time practicing with scrap material to become comfortable with the process.
The difference between a welder and a great welder is a few thousand hours of practice.
Steve
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  #3  
Old 07-31-2019, 10:14 AM
billfunk29 billfunk29 is offline
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Default MIg tacks

I don't do much MIG welding on sheet. But at times it is easy to use one hand to hold the part in place and tack. I will grind the tack down before I TIG. When I TIg the seam, I hammer the sheet between the tacks flush and start and finish between the tacks. It is easier to "drag" the excess MIG filler down the seam if you already have a puddle going. I find if I start on the tack, I leave too much filler at the tack points.
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Old 07-31-2019, 10:43 AM
James. V. D. W James. V. D. W is offline
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Like Steve mentioned, get the fit right and everything else will follow. I like to use .8mm MIG wire as filler when needed. I never use filler from start to finish, but instead only use it where absolutely necessary. If your fit up is nice and tight, you can fusion weld most anything.
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Old 07-31-2019, 11:30 AM
John Buchtenkirch John Buchtenkirch is offline
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IMO your tig bead is too proud with very inconsistent buildup causing you a lot of extra work and less than desirable results. Iíd suggest taking a flat sheet and scribe deep straight lines across it. Then practice flowing those scribe lines together with your tig torch. After you master that (you are mimicking doing a fusion weld) then move on to joining 2 panels together. I use straightened .030 mig wire as filler rod when joining panels for minimal weld buildup but ideally I like to just do a fusion weld. It will take you some practice time to get pretty good but that time will be saved many times over on future jobs down the road. Keep after it. ~ John Buchtenkirch
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Old 07-31-2019, 03:17 PM
mabbo mabbo is offline
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Thanks for all your replies

Took me 3 hours to get this far and Im not happy with it:


If I were to guide coat and block/file it, theres still lots of highs and lows but the overall shape is pretty good.

The bead was really high as you guys point out, once id hammered it all proud, I took the bulk of it off with a 36 grit roloc being careful not to grind the surrounding metal. Then I carried on with the hammer and dolly work.

Im hoping to weld the other side in tomorrow. Planning on fusion welding it this time as Im not comfortable / good enough to use rod. Once tacked I will seam from one side to the other in one go.

I will report back tomorrow once I have done it.

Any more advice / feedback etc appreciated.

Thanks, Neil
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Old 07-31-2019, 08:24 PM
L ee L ee is offline
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Prep: Little or no gap, more time spent here, saves time later.
Tungsten size matters, try a 1/16.
Tack with 30 mig wire or equal tig rod, no rod is the best.
When I do fender flares, I hammer dolly as I go....EASY!
Make sure back up dolly is same shape when hammering.
Do your welds, like 1" or 1 1/2" at a time, end to middle to end.
Or starting at one end and going the whole way to the other end
can work, but you need to let it cool. Don't get in a rush.

Hope this helps,

L ee
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Old 08-01-2019, 01:37 AM
John Buchtenkirch John Buchtenkirch is offline
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Itís highly advisable to try these techniques on some extra sheet or scrap. Donít practice on the car even if itís yours. ~ John Buchtenkirch
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Old 08-01-2019, 04:55 AM
skintkarter skintkarter is offline
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Neil, I've done quite a bit of gas welding on steel over the years and more recently acquired a tig and taught myself to use it.

Fit is the key to both processes. I wouldn't go near tacking with the mig, unless you were prepared to file down all of the tacks so they were completely flush.

My process is to fuse the lot - fuse tack very 25mm or so, tap up the panel to relax (file the tops of anything which is proud) and then fuse the lot in one continuous weld.

Pulse can help to agitate the puddle. I don't use the pedal on steel panel. Reasonably high amps and move quickly. You should end up with a very even HAZ and as per the mantra by Peter Tommasini - do not belt it outside of the HAZ. His vids are very helpful in this regard.

Photos are from some 20swg CRS I used for a guard on the swage I built.

Do you have a tig finger? Propping and being comfortable right along the weld are key. When fusing I prop the torch as per normal, but steady by the cup also with my left hand. Dunno if it's accepted practice, but it works for me.

20141229_180152.jpg

20141229_182835.jpg

20141229_185745.jpg
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  #10  
Old 08-01-2019, 03:04 PM
mabbo mabbo is offline
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Thanks again for the advice, really appreciated

Today I welded in the other side and Im REALLY happy with it. I know its probably poor compared to some of you guys on here, but Im happy considering the last time I tig welded before this week was over 2 years ago.

This time I got the fit up much nicer. I scribed, trimmed with my snips and finished with a file.

This was my process. Please correct me if I could have done anything better.

I cleaned up both sides of both panels then scribed, trimmed and now being tacked into place:


I planished the tacks as I went, waiting for each one to cool as I the panels kept overlapping and I struggled to get them back in line:




I heated either side of the join before putting the tack, unless the fit was really tight. I managed to blow a couple of holes, so once I finished tacking I filled them with rod, then ground flush and planished the seam. In between each tack if I could see light I hammered on dolly to close the gap:


Once happy, I fusion welded from right to left in one go. Quite pleased with this:




Back of the weld looks nice, to me anyway:


I very quickly planished from the right side of the panel to the left, using a hammer with a slight crown and a dolly with a similar shape to the panel. Then I filed it to find the highs:


I covered in blue ink, then sanded with 80 grit on a block and started working from left to right hammering the lows on dolly, using a hammer with a slight crown and a dolly with slightly more crown than the panel to raise the lows. Im about half way through here:


I didnt get a picture of when I finished this stage, this one is pretty much done other than the last few inches:


I then used a slapper and dolly with the same profile as the panel and went over the weld / HAZ. I ran over the repair with 80 grit on the 5" sander set on grind, then finished with 80 grit on DA:


If I went over it again with blue and filed it, it wouldnt be as nice as it looks in the pics... but it is pretty close. I might spend some more time on it tomorrow. I probably had less than an hour hammering after welding.

Im really pleased but always open to advice / how to improve?

Thanks, Neil
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