I "measured once and cut wrong"...

[rngDeadeye]

Hi all

Mig-welding newbie (and it's been 18 months since I welded anything).

I'm restoring a Mk1 Astra GTE and the last piece of the puzzle was fitting an area of floor which was cut from another Astra. I'd neglected the project for a year or so and to get things moving, I went to the unit with the mindset "just get something bloody done"...

So rather than take my own advice and cut the new peice 1cm too big and joggle/plug weld it, I decided to bolt it in place and cut through both the new piece and the existing floor.

I know, stupid.

So now I have a 5mm gap to fill and a smaller gap:

What's the best way to bridge the gap?

It's very thin metal, I do have a chunk of copper so do I use that to weld against or do I just cut a thin strip and put it behind and weld into it?

 

[steveo3002]

whats the other side of those welds look like ?

think its gona need a strip adding

 

[rngDeadeye]

80% of them go right through and slightly proud the other side. The tall peaks, if that's what you are referring to, seem to appear after I let go of the trigger. I had to do half second blasts maximum or it burns through.

 

[rngDeadeye]

For the record, the other welding marks are where I've had to un-pick the cross member from the other car which was used as a stock car and had been seem welded all over.

 

[steveo3002]

yeah they do look a bit proud , im not expert enough to advise really but it would make life easier if you got flatter welds

 

[rngDeadeye]

They will be by the time I've finished but the least of my problems right now.

 

[gulf]

Cut a thin sliver of steel to fill the gap and fill it with weld,once ground down it'll be strong enough and you wont tell its not one piece.

 

[rngDeadeye]

Is it worth making the gap bigger so I'm not welding on an extremely thin sliver?

I just had a thought whilst on the throne - I still have the piece I cut out. Doh! it will be the right shape, just need to weld it back in?

 

[gulf]

Yeah you could cut a bit more out and make a proper 4 sided patch to fit,possibly a
bit longer to do but probably easier for you in the long run.Its nothing major there,a wee hiccup thats easy enough to sort.

 

[mike 109444]

If this is going to be a road going car when done then you might want to get a nice bright light on the floor under the welds to check for missed bit and pin holes. As any carpet you fit will get very wet! When you check for the pin holes, use a marker then go round and re spot them

 

[AndyStobbs]

Anyone tried laying down an O/A or TIG filler rod into the gap to help get some more metal in the joint without endless stop starts.

 

[chunkolini]

I have done that loads of times making sculptures, very easy and quick to do, get it right and there is hardly any raised weld.
Does take practice though.
Use lots of tacks and try to do the weld as a continous run is how I would do it.
Make a few test pieces first.

 

[rngDeadeye]

If this is going to be a road going car when done then you might want to get a nice bright light on the floor under the welds to check for missed bit and pin holes. As any carpet you fit will get very wet! When you check for the pin holes, use a marker then go round and re spot them

It is, I will do exactly that, plus it will be dressed from underneath and painted so it looks nice when you get underneath.

Found a few little holes tonight.

 

[rngDeadeye]

In the end, I couldn't use either of the bits I cut off because I had actually cut the floor in just the right place (I was cutting out someone else's bodgy crap) and the new bit was all dented. So I cut a thin strip and welded that in place.

I found a better setting on my welder to allow longer zaps without burning through.

This is going to be covered with a cross member and have dyno mat on the inside and be stone cipped on the outside so it only needs to be strong and air-tight:

There's a slightly bigger hole the passenger side!

I think I'm going to joggle this side :-)

... or should I butt-join it?

 

[steveo3002]

joggleing just provides another place to rust

 

[rngDeadeye]

I am worried about that.

 

[rngDeadeye]

What about if I joggle and plug weld it from the inside then when I put it on its side I run a seam around the whole thing?

 

[steveo3002]

well yeah weld thru primer , then prime after welding and seam sealer will help prolong its life , but it still has more chance of rusting than a butt join

 

[PSweeney]

well yeah weld thru primer , then prime after welding and seam sealer will help prolong its life , but it still has more chance of rusting than a butt join

most cars are spot welded lap joints on all panel joins. As long as the joint was bright metal to start with, has weld thru primer on the mating surfaces and is seam sealed after this is an acceptable repair