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I can weld, i have been doing it for my job for 18 years now on trucks, so i know a bit, but not on thin stuff really.
So you see these guys doing repairs on say a quarter panel, and they do it with no filler repair,, how do you do that? Every time i weld something, even just by spotting it with a 1mm gap or so, it pulls down, and i cant grind the weld flat like they do.
So, is it me? Or are they just doing something i havnt seen?
How do you finish welds properly?
I have found grinding with cutting disc first, then roloc next, seems to be my best efforts, but still not worthy of no filler repairs... thanks
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Practice and soft pad flap wheels.
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1988 Mercedes w124 superturbo diesel 508hp 1996 Mercedes s124 e300 diesel wagon 1990 BMW E30 V8 M60 powered! 1999 BMW E46 323ci project car
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yes thing is, you put a soft pad on thick steal you get a valley, on thin stuff, you make it really weak, soft pad will run on the flat stuff, then over the weld and then sit back down again on the flat, so its takes off metal from everywhere!
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yes thing is, you put a soft pad on thick steal you get a valley, on thin stuff, you make it really weak, soft pad will run on the flat stuff, then over the weld and then sit back down again on the flat, so its takes off metal from everywhere! I've not had that problem. I use a coarse flap wheel to knock the welds back, then a fine one to finish. These are the ones mounted on an angle grinder, not the drill mounted ones which have too much flex in them.
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1988 Mercedes w124 superturbo diesel 508hp 1996 Mercedes s124 e300 diesel wagon 1990 BMW E30 V8 M60 powered! 1999 BMW E46 323ci project car
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tristanh
Part of things
Routinely bewildered
Posts: 990
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Iirc tonybmw, the Guru that he is, did a thread on this very subject.
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Whether you believe you can, or you cannot, you're probably right.
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1988 Mercedes w124 superturbo diesel 508hp 1996 Mercedes s124 e300 diesel wagon 1990 BMW E30 V8 M60 powered! 1999 BMW E46 323ci project car
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I knock the welds down with a stone grinding disk - using it at right angles to the weld so you don't touch surrounding metal. I then use a power file to get rid of the weld. If the weld is sinking, you need to be panel beating it back level as you go. I'm not an expert by any stretch. Sometimes it works out well sometimes not.
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First things first - you need a decent machine to weld with - using a transformer based MIG dictates the fact that you have to use a stepped control which goes up in amps in fixed increments - so when welding thinner metals that may require for example 50 amps you may well find yourself stuck between 40 - 60 amp stages on a transformer based MIG - 40 amp will probably not give enough weld penetration & the 60 amp setting tends to be too fierce and may burn through - most people at this stage turn the wire feed speed up to counteract this and the net result is that although the weld penetration is achieved you have too much of a weld bead to flush back with the grinder - either side of the weld tends to get thinned whilst the weld bead is dressed back which brings all sorts of problems when truing the panel up. The answer is to use a invertor based MIG whereby you can dial in exactly what amp setting you require to suit the metal thickness that you are welding - that way you can turn the wire speed down and maintain a low profile weld bead - in turn resulting in less to dress back and a neater job all round.
But what are you attempting to achieve - a no filler repair - pretty pointless in my book - I have been restoring cars professionally to very high standards for in excess of 40 years - it will be very difficult to achieve filler less welded repairs on a larger flatter panel - I would much rather have a good strong repair area with good weld penetration and a decent element of thickness to the panels on either side of the weld that the profile is then corrected with either lead loading or a skim of a high quality filler than have repair areas that have been reduced by attempting to achieve a filler less repair that is weak with over thinned metal - Chris
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Last Edit: Dec 6, 2018 8:53:38 GMT by Deleted
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Fillerless welds would be nice but not easy to achieve and very time consuming. I think Chris with his many years of experience and high quality level is a very good source for advice.
For a fillerless welds on an outside panel i think TIG or gas welding is needed as these put less heat and material into the welded area and therefore less deformation. There are people who can do fillerless welding but very few people are willing to pay their bills
Peter
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right i had forgotten about that thread! ill have a full read of it tonight.
Note the fillerless repairs!!!
i think what I'm doing is not leaving enough gap between the panels now, so when ist cooling its pulling down. will have another go today ... thanks for the replies
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I knock the welds down with a stone grinding disk - using it at right angles to the weld so you don't touch surrounding metal. I then use a power file to get rid of the weld. If the weld is sinking, you need to be panel beating it back level as you go. I'm not an expert by any stretch. Sometimes it works out well sometimes not. this - works for me and thats how everyone in the bodyshops ive work at does it
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91 golf g60, 89 golf 16v , 88 polo breadvan
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,710
Club RR Member Number: 34
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If it’s sinking you’re probably getting it too hot at the grinding stage. If you can’t press you’re bare hand flat against it, it’s too hot.
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i have noticed that when grinding welds, the hotter they get the harder they are to grind off. i did try the other day also flattening the weld again with the hammer and dolly, that did help lots too. I think I'm not giving a big enough gap between the panels so when the weld is coling its got no where to go other than bend.
Ill keep trying! thanks
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I've been using the edge of a 3" cut-off disc to bring down welds, just to try to keep the heat down a bit. Obviously proper protection needs to be used (as with anything) and you have to be very careful to make sure it doesn't dig in and start cutting.
I suspect an inverter welder would help me - I think Chris' description above pretty much fits my issue, in that to get the weld about right, I'm probably having to run the wire too fast and end up with too much. But the last time I saw one recommended on here in another thread, it won't run on a standard socket which is a problem for me long before the price comes into it.
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Its not so much a welding or grinding issue. Its physics that you are up against.
As long as molten steel contracts in size as it cools you wont be able to get a perfect surface when welding.
Picture two sheets of paper put edge to edge. Now, span the edges with your fingers and draw your fingers together, pulling on the paper as you do so. Notice how the paper crinkles up? The weld bead is doing the same thing to the metal as it cools down. It does not matter what heat you used or if you let it cool between tacks or if you jumped around all over between tacks. Metal gonna shrink as it cools.
The solution is to align your panels. Make a tack-weld. Grind down the majority of the proud bit. Then with a dolly behind the tack, hammer on the front of the tack. This will spread out the surface area and return the metal to its original state. Repeat for every tack.
It is time consuming.
I try not to worry about it too much. Live in fear of really low CROWN panels and try to weld on the top of CROWNs or near body creases when figuring where to cut in a new panel
There is a tool that puts a slight edge to a panel so that when you weld the weld ends up in the trough of a V and the proposition is that the forces pulling on the sides of the V wont distort the panels as much. Also that the V means that there is less proud weld to deal with when grinding. I have not tried one of these tools yet but would love to hear from any who have.
Link to video
Pete
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Last Edit: Dec 6, 2018 19:28:46 GMT by bjornagn
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thanks! I will try to do more work with the dolly on the panel then. It is all of these little bits that add up and make the job so much better. Ive heard of those tools before, but i think it just hides that you cant do it so well if you know what i mean. I don't know if you have watched any of trevs blog he recommends against this type of tool. Ive got a quarter repair to do on my mini, i want it to be as good as i can get. Ben_O from the mini forum gave me a few hints too today, and i think partly lack of sufficient gap is a big one for me. So key points good alignment of panels sufficient tacking grinding and realigning panels short runs of welds clean with a cutting disc or soft pad roloc disc ben said also make sure when grinding don't use any pressure on the grinder, pressure makes heat and that makes the job distort. da, thanks
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I've been using the edge of a 3" cut-off disc to bring down welds, just to try to keep the heat down a bit. Obviously proper protection needs to be used (as with anything) and you have to be very careful to make sure it doesn't dig in and start cutting. I suspect an inverter welder would help me - I think Chris' description above pretty much fits my issue, in that to get the weld about right, I'm probably having to run the wire too fast and end up with too much. But the last time I saw one recommended on here in another thread, it won't run on a standard socket which is a problem for me long before the price comes into it. My 180 amp invertor welder will quite happily work on a standard 13 amp supply all day long
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Last Edit: Dec 8, 2018 8:24:00 GMT by Deleted
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my 180 amp blackline £223 welder is on a 15amp feed, but works well...
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did a bit to my mini today and i can see where ive mainly been going wrong now thats not finished, bit i welded the panel into the quarter today, and main difference is i left a 2mm gap to weld. With the 2mm gap, i could get teh weld right in, i know its penetrated to the root, its taken less time to weld as the weld is going into the panel, not having to melt into it, and that is what ive been doing wrong thats the penetration. Checking afterwards with a hack saw blade, the panel is much much better than i have done before, and that was towards the middle of a big panel too. Just need more practice now, and ill be happy, significant improvement today. thanks for the help
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