Welding Tips – The Earth Lead

Welding Tips: Episode 1  – The Earth Lead

Irrespective of which welding process we are taking about, one thing that will give you more grief than pretty much anything else is a bad earth which is why I’m starting here.  Keep in mind we are talking about an electrical circuit and if you put any form of resistance into an electrical circuit, it will produce a certain amount of heat as well as dropping back your current.  A bad earth will do the same thing in welding.

If you find your earth clamp is getting very hot (and I have seen them set fire to the rubber insulation around the cable at the clamp end) or find that you have to constantly change the settings on your machine despite not changing the welding material thickness etc, then there’s a 75% chance it’s a bad earth that’s causing it.

Before you attach your earth clamp to the job, make sure you have a clean surface, free of dust, dirt, grease and rust. If necessary, grind a spot on your job to clean it up and get a good contact.  Every bit of rust etc will act like a resistor in an electrical circuit, producing heat and possibly changing the whole characteristics of your weld by dropping the amperage.  Also check the actual contacts on your clamp for splatter, corrosion or crap on them which will do the same thing.

Check the lug that is on the end of the cable and (usually) bolted onto the clamp. If it’s rusty, cracked or looks a bit suspect, change it and/or the bolt as well.  They only cost a couple of bucks and can save you a lot of grief.

Check that the earth lead connector on your machine is firmly fixed onto/into the machine itself.  If it’s a lug like the clamp end, look for the same problems.  If it’s a “push in and turn” connector (commonly referred to as a Dinse Connector), ensure it is firmly locked into the receptacle or it will arc out inside and you will need to change the panel connector on the machine.  That can be a pain and also cost a bit.  They’re not usually something shops carry on the shelf and you’ll have to order one in so you will be having down time as well.  If you need to buy a new Dinse Connector check the size.  There is a small one with the male “prong” about 10mm in diameter and another about 13mm in diameter.

If the rubber has melted back or perished on either end, don’t panic.   Most of the time you don’t have to buy a new lead, simply trim the cable back 50mm or so until you get bright, shiny wire and fit a new lug or connector if necessary.  If you find the wire inside is still black after 500mm or so, then it’s probably time to get a new earth lead anyway.

Occasionally the manufacturers will fit a cable or earth clamp that is underrated for your welder and no matter what you do, you will still get a red hot earth lead or clamp.  In this particular case, you have no option but to change the cable and replace it with a heavier one.  There’s no need to go stupid and use a big, heavy cable, it’s not going to achieve any more than going up one size in diameter which will probably fix the problem.  If you do have to change the cable, don’t go overboard on the length either.  You will find yourself tripping over the excess cable at times and it’s cheaper to move the welder a metre or two than pay for a longer cable.

Finally, if you are replacing the cable, take a piece of the old one with you so you have something to judge the diameter by.  Cables have a weird system of measurement where they use the cross sectional area of the cable rather than the diameter. For example, a cable of about 8mm in diameter is referred to as 25mm and it’s easier to walk into a shop and say “I want 5 metres of this, please.”

That’s it for now. I hope this was of some help to you.


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