Repairing Blow Throughs - Ground Too Thin

[JonnyAlpha]

Hi;

Did my first major repair this weekend, but welded a boot floor panel on an Austin Mini.

The weld went reasonably well, not brilliant (small bits were) but its sure not coming apart.

Anyway when I was grinding away the excess weld I got a bit carried away in one spot and ended up turning a small area into tin foil (just smaller than 20p size) anyway in a rush I thought Id weld it over and of course just ended up with a hole (pics attached).

http://i1043.photobucket.com/albums/b436/JonnyAlpha/IMAG1249.jpg

http://i1043.photobucket.com/albums/b436/JonnyAlpha/IMAG1245.jpg

Whats the best way of repairing this kind of hole without apply a patch!!

Iv'e read about plug welding using copper and brass behind the hole but what technique?

 

[shenion]

You can back it with a copper plate.

I just do real short bursts around the hole. Make it real thick at that point but works. Once you make a full circle, you can fill it in with longer welds.

 

[200T]

Hi!

And hold the torch almost horizontaly, resp. aligned with the sheet. I feel this also helps to build up the edges.

It's a good thing to practice this way of repairing repairs

Do you have an angle grinder with adjustable speed? I found it very helpfull to reduce speed to 1/3 or so when grinding down welds on thin metal.

Cheers,
Jan

 

[JonnyAlpha]

By horizontal do you mean almost laying the torch on the sheet? And fraid not my Grinder is off or on : (

 

[steveo3002]

with the brass or copper just push it up tight from behind and weld away in short bursts

id really have a look at how you are grinding , you should have noticed before it got that bad , i use a hard stone wheel to tickle the tops off the weld being carefull to not touch anything but the weld , once its really close then use the flap wheel with some care

 

[200T]

By horizontal do you mean almost laying the torch on the sheet? And fraid not my Grinder is off or on : (

Yes, that's what I meant

Can you get these discs where you are?

They allow you to see through them when they spin - I use them for grinding tricky welds. Expensive but realy good for grinding back welds as you can see what and where exactely you are grinding

Cheers,
Jan

 

[JonnyAlpha]

with the brass or copper just push it up tight from behind and weld away in short bursts

id really have a look at how you are grinding , you should have noticed before it got that bad , i use a hard stone wheel to tickle the tops off the weld being carefull to not touch anything but the weld , once its really close then use the flap wheel with some care

I should have been more careful, i'll look at getting some kind of grinding attachment and use it before the Flap Disc. As I was grinding I should have known if the metal starts to discolour its getting thin!!

I guess I just got carried away with all the excitement!!

 

[JonnyAlpha]

Yes, that's what I meant

Can you get these discs where you are?

They allow you to see through them when they spin - I use them for grinding tricky welds. Expensive but realy good for grinding back welds as you can see what and where exactely you are grinding

Cheers,
Jan

Not seen any of those, the ones I use were these: http://www.weldequip.com/ceramic-flap-discs-115mm.htm

Very effective!!

 

[Zagan]

Um mar!

Didn't disconnect the battery!

tsk tsk.

hope you covered the glass too.

hopefully you haven't blown any electrics in the car.

just build up the sides while allowing weld to cool then go again.

 

[outofthefire]

Um mar!

Didn't disconnect the battery!

tsk tsk.

It looks like the battery is disconnected he just covered the cable with tape. If you dont have any copper to put behind the hole ally works as well.

 

[JonnyAlpha]

I disconnected the battery when I was welding, didn't know I needed to though. Just reconnected it (and the fuel tank) to move the car, couldn't get it started though. Why cover the glass???

 

[Robotstar5]

Why cover the glass???

grinding sparks will melt into the glass

 

[awemawson]

And grinding sparks can explode a battery. When a lead acid battery charges the gas given off is a mixture of hydrogen and oxygen in exactly the right proportions to explode. Once I lost a pair of glasses that were smashed on my face by a battery exploding as I removed the charger croc clip and it made a small spark. Always turn off at the mains now! Your battery should have been removed completely if welding near it.

 

[JonnyAlpha]

Dangerous stuff this!!! My battery was removed when I was welding but only in that pic as I put it back to move the Mini. Didn't realize about melting glass but my grinding was no where near the glass, did burn my hand though, grinding sparks burnt through my grinding gloves.

Thanks all.

 

[outofthefire]

I've ruined countless cups grinding to close to them, it makes them none slip but they go rusty after the first wash

I'd have removed the battery welding in a mini boot but at work we just cover the wagon batteries with a either a bit of old curtain or a sheet of ally but thats because we have to use surge protectors rather than disconnecting the batteries.

 

[Angusdog]

I've got the T shirt from grinding too close to my mini's glass. Also it pays to bear in mind where the sparks end up - they're like ickle 'rust seeds'