Newbie

[minimetro]

Hi,
I'm about to attempt welding on my car, first question is,

I have practiced on scraps of metal, no problems, however I am concerned about electric shocks. I intend to weld a piece to the floor near the inner sill, but I need to be in the car when I do this.

Is this safe? where is the best location to position the earth clamp? as it cannot be located on the floor could it be located to the top of the sill? I have read stories about electric shocks, I just dont want it to happen to me.
Apologies for the silly questions.

 

[Wozzaaah]

No problems at all with shocks, though the current may be high the working voltage simply isn't high enough to do any harm.
Ideally, you should site the return clamp as near as possible to wherever you're welding. Just make sure that wherever you clamp it it makes a good connection and you're fine.

Do I get a prize for guessing what your project car is?
Welcome to the forum.

 

[shenion]

It is a fairly low voltage, not much more than a car battery.

Earth clamp should be as close to as possible to the work being done. Must be a good, clean connection. The sill should be ok.

Main issue is fire safety. Fuel lines may run under floor or near wor. Underseal will catch fire.

 

[minimetro]

Cheers for the advice,

Its a british car, they are known for rust and they are similar to a mini, any ideas?

 

[Wozzaaah]

Errmmm...let me think....

Get some pics up in the projects section, not many of those about now.

 

[rtbcomp]

Hi Minimetro, I'd say it is a Mini Metro.

In my experience the biggest shock you'll get is just how much rust there is under the carpets.

 

[minimetro]

Its the Rover 114 GSI, they are starting to get rare, the Austin metros are like hens teeth, will get some photos up soon of it. Again thankyou for the advice.

 

[Sid]

Only thing I'd add to what the others have said, is to make sure the car's battery negative lead is disconnected.

 

[FranV8]

I heard it was a good idea to disconnect the alternator too, as otherwise I think it risks the diode pack?

 

[Ed.]

No problems at all with shocks, though the current may be high the working voltage simply isn't high enough to do any harm.

Welcome to the forum.

Sorry Wozzaaah, have to disagree with you on this one.

I think that you have mixed them up. It is actually the current that will get you. 60mA is all that it takes to stop your heart if the current goes though it or near enough to it. Voltage isn't usually an issue, an example is when you get zapped by a static electricity, the voltage is in the thousands of volts but very low amperage. Your skin if dry, does provide some resistance to electricity which helps to stop the current going through, so a certain amount of voltage is required, so the more voltage the less resistance and electricity does start getting through. If the electricity goes from one arm through the skin to the other arm then you get a jolt, but if through one arm through your body and heart, and then out through your back to complete the circuit then you could be toast.

The voltage on a welder is more than high enough to permit electricity to go though your skin, about 2 years ago in the middle of summer I was welding up a garage frame 3.3mt in the air straddling a RHS beam with my legs on both sides whilst I MIG welded another beam, my clothes and gloves were sweaty along with the rest of me, I had finished the weld and wanted to get in a better position to do another weld.

Instead of putting down the torch and repositioning myself I just tried to jiggle my self into a better and more comfortable position whilst holding on to the gun. I accidentally pressed the trigger and as the wire fed out it hit my gloved left index finger, as the glove was moist through sweat the current went from the gun, the glove, my knuckle and to the frame.

My knuckle was sore for about 6-8 week. Fortunately for me, my left hand was pressed on the RHS so the electricity only had a short path to complete the circuit, had my left hand been lifted slightly above the steel, that current would have tracked from the wire and through my hand , arm and through my body to the next available earth and would have been though my butt and associated bits. (think about it ) as my jeans were also sweaty.

So either potentially near or through my heart and out though my other bits. Had it done so I probably would have been killed or fallen off on to the concrete floor below, probably with the same result, or at the very least would have brought tears to my eyes for a very long time, if you know what I mean.

60mA is nothing compared to 100-200 amps or more when welding.
I considered myself to be very lucky that day.

As to positioning the work clamp, as close to the welding and away from you, so if you are welding in front of you, put the clamp on the opposite side of where you are welding, that way the current should go away from the weld to the clamp and not past your body to the clamp. Just my 2 cent worth.

 

[madkayaker]

the current will not flow through you if your in the car unless you stick the earth lead on your foot or any other dangling bits and then try welding 60mA is indeed enougth to put you in the hole but with a welder it doesn't work! have had a few belts off stick set when trying to change sticks on wet grass and that's off a 200A set on max you will only get the current if you have the short circuit

 

[Ed.]

the current will not flow through you if your in the car unless you stick the earth lead on your foot or any other dangling bits and then try welding 60mA is indeed enough to put you in the hole but with a welder it doesn't work! have had a few belts off stick set when trying to change sticks on wet grass and that's off a 200A set on max you will only get the current if you have the short circuit

I think that would depend on the path that current took. If you had the work clamp attached to the car and were kneeling down with moisture in the kneecap area and if there wasn't any insulation such as paint, you would probably be zapped if you changed stick with with your bare hands touching the electrode end. The path taken would depend if it tracked through your skin or through your body and if it zapped any of your nerves along the way.

Either way it is a mute point really as it is a bit like Russian roulette, it only takes one wrong spin. Most zaps don't do any lasting damage, but it only takes 1 to go the wrong way and you will become toast. The point I was trying to make was that it only takes 60mA to kill and not the voltage and a welder certainly has thousands of times more current that is necessary to kill. So why take the chance when you can minimize the risk easily.

Welding by definition is risky and 99.999% of the time is safely done, it's that tiny, tiny, percentage that will get you if your not careful.

So why take the chance, put the clamp away from you where possible and make the current head towards it and not you, don't potentially put yourself at risk by becoming part of the circuit. It's good welding practice.

 

[rtbcomp]

The voltage drives the current, so if there isn't a high enough voltage you can have a million amps availaible you won't get a shock.

Even though you place the earth near to where you work some current will take all sorts of paths through the body work. Consider the shell as a load of resistors in parallel, some current will flow through them all, so as regard to electronics in the car best be safe than sorry and disconnect them.

A welder, especially a buzz box is a spark machine connected to an inductor, this will induce high voltage spikes and it's most likely these that give you tingles whilst welding.

You can get a shock of 50 volts, ask any BT engineer!

 

[Ed.]

So the end result is that I think we all can agree on is that, Yes.. there definitely is more than enough juice in a welder to kill you, if you are unlucky or don't take precautions. Do a google search with "welders death electrocution" and you will find a heap of info. People do die regularly when welding due to a whole heap of reasons.

At the end of the day, it isn't worth taking chances and you do what you can to minimize the risk, this goes for all power tools and not just welders.
You can even weld underwater in the ocean, provided you have the right equipment, know what you are doing and if you take precautions it becomes safe.

 

[Wozzaaah]

Sorry Wozzaaah, have to disagree with you on this one.

I think that you have mixed them up. It is actually the current that will get you. 60mA is all that it takes to stop your heart if the current goes though it or near enough to it.

I don't disagree with you there Ed but as RtbComp says, the voltage has to be high enough to push the current through you and on the average mig welder it simply isn't.
And, as he also says, MMA (stick) machines often have 50 or even 80 open circuit volts which most definitely is enough to give you a bit of a tingle in the right circumstances.

Take a car battery for instance, what happens if you touch both terminals with something metal? Big bang, a fat spark and a brown mark in your grundies. Now touch the two terminals with each hand, what happens? Zilch!
The cold cranking amps on a 12V battery can be well up in the 600-700+ range but at 12V there's simply not enough volts to hurt you.
If welders were that dangerous then they would not be on sale.

 

[Ed.]

As I said earlier, dry skin has a certain resistance to electricity so when you touch a 9 Volt PP3 batterys terminals you don't feel anything, same goes with a 12 Volt car battery. If you use your tongue to test the the 9 Volt PP3 battery your tongue tingles. That is because the resistance is lower and the current starts to flow through your tongue muscles.

However there is no way that I would try that tongue testing trick with a 12V car battery. I would imagine that the results would be quite damaging to your tongue amongst other things.

"Quote" The cold cranking amps on a 12V battery can be well up in the 600-700+ range but at 12V there's simply not enough volts to hurt you.
If welders were that dangerous then they would not be on sale. " end Quote".

As for dangerous thing being not allowed for sale....Think of how many cars are sold yearly? Drive safely and pay attention the're relatively safe, drive like a fool, not pay attention and speed and that's why we have a high national death toll, but you can still buy them.

So essentially your skin is a light electrical insulator, remove the skins ability to insulate by having sweaty skin or clothes on, or having water touching it and the whole ball game changes.

Most of the time you will get just a tingle or light shock but it is that very tiny percentage when conditions line up and your luck runs out that it will get you and it does happen. So better to be safe and take precautions than to hope for the best.

Seeing as a welder can put out 50-60 Volts and hundred of amps the machine is more than capable of killing as it did in the following links.

Two links I found regarding welding deaths, the common denominator was water and/or sweat or something that lowers the skins resistance..

http://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=201360872

http://www.jniosh.go.jp/icpro/jicosh-old/english/cases/cases/case113.html

But I feel that this post is diverging a bit from my first posting where I simply stated that it is actually the current (which only requires about 60mA plus) that will get you, and not the voltage. Just trying to set the facts straight.

Both of which a welder can output easily and under the right circumstances can get you killed.

 

[Wozzaaah]

Ed, please don't think I'm being picky but both your links refer to deaths by MMA welding, not MIG welding! Mig welders putting out 50-60 OCV are VERY uncommon.
I'd almost stake my house that both those deaths refer to welding using AC (one clearly states it was) which, according to several articles I came across, is considerably more dangerous than DC and as they both refer to welding on a large scale, the sets quite possibly had OCVs of something like 80.
The OP is using a mig welder, they typically have a range of something like 17-36V DC.

We have many thousands of members on here and as far as I know not one of them has been electrocuted by their machine.
I think we should let this lie, we'll just keep going round in circles if we don't.

 

[Ed.]

No problem, we all have different opinions which doesn't prove either one of us is right or wrong, however I will still always err on the side of caution. What I do know however is that if that jolt that I received from my MIG on my hand was anything to go by, if it had gone near or though my chest instead of just through my knuckle I would not be here today writing about it. Cheers.