23 replies to this topic

[sonikk4]

 

 

 

I myself have pretty much only just got to the point where I'm not constantly blowing holes and swearing

Im at swearing stage now.

A tip for you if you are not aware. I use a piece of copper pipe, sliced lengthwise and then flattened. I then add a couple of slots for intergrips and then use this as a backing piece for any butt welding i do especially on floors. This helps you to prevent blowing holes through.

Thanks for that tip mate. Can I use the flattened copper behind holes Im welding up, such as old bolt holes because at the moment the holes get bigger before they get smaller!

 

 

Yes you can, as long as you can get behind then happy days.

 

Once you get more confident with your welding you can start to do away with the backing copper.

 

I will say this from experience when you butt weld thing sheet steel ie mini floors you will need a small gap. 1mm which is the thickness of an intergrip is more than enough. the reason behind this is if you your metal is butting up against each other the metal will pucker when you weld. This means when you go to knock back the weld you will thin the welded joint out. Then it will fail.

 

So a technique as mentioned by Avtovaz is to pulse weld instead of seam welding. So this method is essentially a tack weld but you hold the torch on a short period longer. this will ensure you get decent penetration. When using this process slightly overlap each pulse weld which will give a nice series of Dimes overlapping each other. 

[stuart bowes]

well that's interesting then definitely ignore the bit I said earlier about a tight fit I suppose

 

ironically the only bit of welding I've done that was structural so far was a section of inner sill, and that actually was done with gaps. the reason I stopped doing it that way was the number of blowouts and watching a series of professional-seeming youtube instructionals saying don't bother with the gap you don't need it for thin sheet.. so now I am a bit confused

 

one one hand I want to do it well, so I'll have to go back to a slight gap and pulsing, on the other hand i don't want to go back to all the annoyance and it seemed to be working fine?  checking the other side and seeing good penetration.. though like you say I am having to grind a lot down on the visual side

 

every day I do a bit more messing about with the welder and I'm definitely getting more confident with it either way

Edited by stuart bowes, 17 July 2022 - 08:44 PM.

[Vanman20]

For welding up small holes use a copper coin, I keep a 2p piece on my welder for just such events

[DeadSquare]

Once you get more confident with your welding you can start to do away with the backing copper.

 

I will say this from experience when you butt weld thing sheet steel ie mini floors you will need a small gap. 1mm which is the thickness of an intergrip is more than enough. the reason behind this is if you your metal is butting up against each other the metal will pucker when you weld. This means when you go to knock back the weld you will thin the welded joint out. Then it will fail.

 

So a technique as mentioned by Avtovaz is to pulse weld instead of seam welding. So this method is essentially a tack weld but you hold the torch on a short period longer. this will ensure you get decent penetration. When using this process slightly overlap each pulse weld which will give a nice series of Dimes overlapping each other. 

 

Under adverse circumstances, poorly butt welded seams will rip open like perforated paper.

[sonikk4]

well that's interesting then definitely ignore the bit I said earlier about a tight fit I suppose
 
ironically the only bit of welding I've done that was structural so far was a section of inner sill, and that actually was done with gaps. the reason I stopped doing it that way was the number of blowouts and watching a series of professional-seeming youtube instructionals saying don't bother with the gap you don't need it for thin sheet.. so now I am a bit confused
 
one one hand I want to do it well, so I'll have to go back to a slight gap and pulsing, on the other hand i don't want to go back to all the annoyance and it seemed to be working fine?  checking the other side and seeing good penetration.. though like you say I am having to grind a lot down on the visual side
 
every day I do a bit more messing about with the welder and I'm definitely getting more confident with it either way

Having done three fully body restos including a lot of floor work etc and over the years on other cars ( I’m not a professional by the way) it makes sense when you think about it. As you weld the surrounding metal heats up and expands, hence the puckering. Now on thicker metal it’s not such a big issue plus you have more leeway with knocking back.

Due to the way the metal reacts, the weld buildup on both sides, it’s difficult to hammer and dolly flat with knocking the welds back first. I have tried several different techniques over the years and since I have started using inter grips I don’t have the issue with metal thinning. Plus I also use the copper backing technique as well to help prevent blowing holes. Even experienced welders do blow through occasionally. BUT another thing to consider here is the tooling you use to knock welds back.

I use a standard grinding disc to knock the tops off, then a flapper wheel. Even with the flapper wheel you can over do the knocking back and end up “ blueing” the area which will mean it’s thinned down. I use finish off with a high speed pneumatic 90 degree die grinder using Roloc discs.

I will either seam weld or pulse weld depending on the area I’m working.

[stuart bowes]

similar, I've been using a powerfile (carefully) to take away the worst, then a flap disc either on the regular grinder or a smaller one on the air line, mostly depending on the available tool-wielding space available

 

I want to leave everything flush as can be, but on the other hand due to possible thinning out like you say, I've been leaving it 'near' flush instead where it won't be seen (i.e. the outer sill is going over the top, or the flitch panel repair which is behind the A panel, etc)

Edited by stuart bowes, 18 July 2022 - 09:34 AM.

[Spider]

There's also a MIG wire - 'Easygrind' - available. It leaves a less hard weld for grinding back, so there's less likelihood of thinning the surrounding metal. I have at times also soften welds by heating them with the Oxy after welding.

 

I was using flap discs a while back for sheet metal, but I found sanding discs in the grinder, on a soft backer better in that I had less likelyhood / more control where it came to thinning. I do find though, that I go through the discs quite fast compared to the flappers.

[weef]

I posted a link on 23 May  2018 on my method to weld thin plate. It involves swaging one of the repair edges, welding up then grinding off the swaged metal to give a flush finish.

The advantage of the swaged edge is that there is no butt weld and you can run short continuos welds, and the swaged edge eliminates distortion to a certain extent.

Someone on the forum will be able to sort out this link I reckon

[jonlad]

I have a small portable rechargable LED work light for getting more light on the workpiece. It really helps when in a dark spot like a wheelarch or underneath a shell.

 

something like this but much cheaper from fleabay

https://www.screwfix...wE&gclsrc=aw.ds

 

my welding leaves much to be desired too but keep at it, have patience and keep a grinder/sander handy!

Edited by jonlad, 27 July 2022 - 02:46 PM.