Earth connection when welding car: problems

[russ_1380]

hi everyone

I'm still trying to put patches on my polo and I'm struggling like hell!

I am using a Clarke 135te Mig with straight CO2 and 0.6 wire.

When welding the patch to the floor panel I can't seem to get that nice fizzing / crackling noise, I am hearing a popping / machine gun noise.

The weld never seems to flow between the new panel and the original floor panel; this is my main problem and is driving me insane.

From reading around I am guessing this is down to a poor earth connection. So far I have:

Turned the power down
Turned the wire speed up
Gone in small spots rather than long runs.

All of the above tips help but I still think its the earth that is the problem.

My question is how should I attach the earth cable? I have cleaned to bright metal on the new patch I'm putting on and to bright metal on the original floor panel. I then put the earth clamp on the lip of the sill as near as possible to the area to be welded. (the earth clamp isn't actually touching the metal patch though).

I read on here that you can temporary weld a threaded stud on to the car then bolt the earth cable down. Is this likely to help at all? PLus daft question, but if i did this should i put the stud on the new patch or the original floor?

Many thanks

Russ

 

[rtbcomp]

Are you using the original Clarke earth clip? If so you would benefit from a screw-down type.

On my buzzbox I've fixed a bit of copper pipe with a flattened end to my earth and fasten it to the workpiece with a G-cramp.

 

[gavuk]

I often use fixed parts of the door lock ,the catch plate ,or grind some paint away and clamp or weld to that ,,,,nearer is better

 

[Windy Miller]

Grind a clean patch on the lip of the sill and clamp some mole grips to it. Clip your earth lead to the moles and away you go!
Alternatively clip your earth clamp on the cars earth lead, with the battery disconnected of course!
I have used both of these methods for years and never had a problem, but as said earlier, you REALLY need a decent earth clamp. Those cheap jump lead type things are hopeless. Machine Mart do some decent ones at a reasonable price and you will find a massive difference!

 

[pedrobedro]

Machine gun popping could be the wire pushing back because the feed speed is too high. You need a good earth though.

 

[russ_1380]

Cheers guys.

I'm going to use a temporary mod to the earth clamp. The car is off the road so getting to the shops is going to be a pain....

I was thinking of squashing the earth clamps jaws flat (it looks like pressed / folded steel at the mo) and then wrap some sheet lead around the jaws, making the contact area flat. If you see what I mean

I'm hoping this might be a quick fix in the mean time before I purchase a nice new clamp. Looking online, I think I'll get the screw down type next time.

 

[gavuk]

If the earth clamp is that bad ,use mole grips or clamps over it or attach the earth wire to a clamp,you asked if its ok to weld a stud ?....no problem .....if your struggling getting a stable arc ,try increasing amps and using thin technique esp as your using co2,then adjust wire speed as per tutorials ,use your ears ...try striking an arc and adjusting wire feed at the same time ,much easier to see too slow and too fast

 

[russ_1380]

cheers guys

I have now finished the welding! Wooooooooo!

Just need to tidy them u a bit wi filler and underseal over it.

Thanks for the advice.

If I was to do it again I think I would take more time cutting the patches, I think art of the problem (along wi the dodgey earth) was the fact that there were sometimes small gaps between the floor pan and the patch. This obviously did not help me at all.

Off subject a bit but do any of you use oxy acetylene welding for patches on cars?

Russ

 

[gavuk]

oxy /acetylene used to be the prefered process for welding cars before mig ,it fell out of favour due to cost (rental/insurance) and distortion...and migs becoming cheaper etc...it is still the first choice of some old timers,..

 

[brightspark]

oxy /acetylene used to be the prefered process for welding cars before mig ,it fell out of favour due to cost (rental/insurance) and distortion...and migs becoming cheaper etc...it is still the first choice of some old timers,..

<<<<<<<<<<<<<<<<is an old timer i wouldnt part with mine . its a bit slower than mig .neater than mig. easy to weld disimlar thickness of metals with . but as said probs a bit more distortion on pannels insurance ect

 

[gavuk]

.......I would have cylinders too if money was no object, I learnt on gas (industrial) and loved it ,most places i've worked don't have acetylene nowdays ,,,preferring propane because of insurance and firebrigade recommendations ......it certainly has its place ,and made tig welding easier to learn too....