will i harm my mig

[Shedendman]

I'll try and make this clearer than mud,i've knocked up a welding trolly for my mig,the mig is bolted to the top of the trolly,i find that now i want to weld a few bits to the trolly,using the same welder,will i harm or do anything wrong to the welder itself,or shall i unbolt it from the trolly and have it separate as in not attatched to the trolly?
I know dumb question,but i thought i'd ask

 

[wotwot]

DONT DO IT IT WILL #@#@ IT RIGHT UP DONT DO IT UNBOLT IT DONT DO IT check out my miserable post.

 

[Shedendman]

DONT DO IT IT WILL #@#@ IT RIGHT UP DONT DO IT UNBOLT IT DONT DO IT check out my miserable post.

Reply confirmed,I WILL UNBOLT IT

 

[wotwot]

Sorry but did'nt wont you to do what I did.
Its a bit like standing the welder in the vehicle you are welding,and if its touching bare metal it is earthed and it will go poof bang as mine did.

 

[rtbcomp]

......... check out my miserable post.

Any chance of a link please?

 

[the snooper]

here is the link to wotwot's miserable post

 

[wotwot]

Sorry again i'm hopless at putting links in ,

 

[aametalmaster]

Sorry i don't agree. I have welded with metal leaning against my welder as well as one bolted to a truck bed and welding on the same bed as in a vise and nothing happened...Bob

 

[Hitch]

Agree with Bob, unless you have a problem with the machine, like insulation breaking down, it should be isolated from the machine casing I believe. Done it plenty of times. Or having the welder sat on the bench or job.

I think that your machine must have had a problem prior WotWot.

 

[rtbcomp]

+1 for Bob & Hitch, except if the workbench is connected to mains earth and welding earth and the welder's frame is in electrical contact with the bench you could get current in the mains earth lead which may damage the welder.

If the welder is isolated from the bench but the earths are connected as above there could be a potential difference between welding earth and mains earth inside the welder, which may cause problems.

That said, a well designed machine shouldn't experience problems and I reckon inverter machines would be more susceptible than transformer models.

 

[wotwot]

I dont believe I would get a senior member and a moderator condoning potentially dangerous welding habits, this is a great site and should always approve safe welding.
Hitch my post clearly states what happened with my machine,maybe you should clamp the earth of your machine to its own metalwork and then put a spot of weld on the earth clamp, I suggest you would be making repairs to your own welder.
aametalmaster just because nothing happened yet does not mean it wont happen.
Would'nt it be best advise not to rather than say "dont worry it will be fine" safe rather than sorry I think.

 

[Shedendman]

Thanks for the advice gents,as it is an old mig i'll play safe and unbolt it. Cant afford anymore mishaps

 

[Hitch]

I dont believe I would get a senior member and a moderator condoning potentially dangerous welding habits, this is a great site and should always approve safe welding.
Hitch my post clearly states what happened with my machine,maybe you should clamp the earth of your machine to its own metalwork and then put a spot of weld on the earth clamp, I suggest you would be making repairs to your own welder.
aametalmaster just because nothing happened yet does not mean it wont happen.
Would'nt it be best advise not to rather than say "dont worry it will be fine" safe rather than sorry I think.

As I said above. Sometimes if reach is a problem, the machine gets pulled against the job, or something is leant against it whist welding. Or the feeder is sat right on top. No issues so far, in 13 years.
I wont go and do it today though, because my garage is full of wood dust at the moment.
Now that would be potentially dangerous.

 

[Engineer]

Why bother to take the risk of a burnt out machine, in order to save 5-10 minutes work unbolting? Also worth remembering that a pro standard machine, is able to stand a great deal more abuse than the DIY type Chinese/Italian sets, a fair number of those posting here seem to own.

 

[madkayaker]

there should be no connection between the output of a welder and the earth on the case.if there is then there is a fault on the welder that is potentiality dangerous e.g. current running to earth. therefore welding with the case touching the work should have no effect on the welder. if it dos then there was a fault on the welder

 

[rtbcomp]

You're missing the point, we're talking about having the welder standing on the workpiece and under those circumstances it's perfectly possible to have a connection between the welding and safety earths, which could lead to problems as I mentioned in Post #10

 

[keith19]

Interesting, MK, but can the earthed case pick up any of the welding current and divert it to mains earth, if it is in contact with the job?

There's two points that need noting, as they can easily get mixed up in the excitement of Wotwot's post:

1. "On a couple of occasions recently while working on my very rusty 1978 vw bay window I have had the welder inside the van to keep it dry or out of the sun. As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea )."

After this experience perhaps some of us would have stood the welder on a bit of wood, or a rubber mat. Or even made up a new foot. It looks like the case touched the job and picked up welding current? Most small mig and arc welders are earthed inside the case to mains earth for safety, unless they are double insulated. I would imagine most top quality pro machines are double insulated.

2. "I dropped the torch on the welder which landed exactly on the trigger, as I dropped it knee jerk reaction made me grab for it in doing so I knocked the earth clamp of the piece I was working on and landed on the welder torch tip touched earth clamp and FLASH and POOF is all I can describe it as.The combination as you would expect caused my welder to try and weld itself."

This was purely a freak accident. The welder shorted out. It had nothing to do with being inside a vehicle. It could have happened anyplace, in the garage, on the bench, etc. We've all (almost) had accidents like this.

So long as a small hobby mig or arc welder is insulated from what is being welded, either by its plastic feet or a rubber mat or piece of scrap wood etc, no harm is likely.

Years back we were taught to always seat the welder itself on an insulating mat if it had to go inside a vehicle, (usually vans) whether it was arc or mig. I was always a bit vague about the electrical technicalities of why we had to do this, but always complied to avoid a H&S rollicking. We just used the van front footmats, always available. Occasionally they went back with holes in, or curiously misshaped...
Maybe years ago even small pro welders weren't double-insulated?

 

[Hitch]

So your in a steel framed building, and you want to weld a bracket to a leg of it.....
Obviously the frame is bonded to Earth on the electrical system.... So that makes the casing of the welder connected to the building....so you prepare to weld, connect the earth clamp to the building, so then the earth clamp and welder casing are both connected....

I must point out, that the 'earth' on a welder, isnt really an earth is it, its a 'return'.

 

[keith19]

Unless the welder casing is double-insulated?

 

[madkayaker]

current from the welder will only flow around the output circuit of the welder. it would only flow to earth if there was a fault on the welder.