Scorch/melt on ground clamp

[joshuabardwell]

I noticed a scorched/melted part on my ground clamp today.



My best guess is that when I had it clamped on the table, the woven copper bridge between the two jaws arced to the table, as shown below.



It could also be that the woven copper bridge arced to the clamp itself, but that seems unlikely, as it would seem to be an unavoidable design defect, and this is a pretty standard design for a ground clamp.

 

[CNC Dan]

yes, if your table is painted or rusty it might not make good contact. I like to twist the clamp back and forth after clamping it on to let the copper jaws rub through any 'gunk' to make better contact.

 

[k0ua]

Yep, that is what happened, I had it happen to me a couple of times too, from not having the contacts on good clean metal, and the braid was touching bare metal.. happened on the lip of a FEL bucket, too much paint further back but the edge where it touched the braid was bare... whoops.

 

[joshuabardwell]

It's odd, because the "teeth" of the clamp were on clean, bare metal (the table top). But I know that anywhere there's a small gap will arc, so my guess is I shouldn't have put the clamp so deep on the table.

 

[joshuabardwell]

I wonder if it would be worthwhile to paint the braided strap with paint-on electrical tape, to prevent this from happening in the future.

 

[k0ua]

I wonder if it would be worthwhile to paint the braided strap with paint-on electrical tape, to prevent this from happening in the future.

That might not be a bad idea. I hadn't thought of that.

 

[joshuabardwell]

That might not be a bad idea. I hadn't thought of that.

I'm also thinking I may have some heat-shrink that would fit perfectly, which is nice, because I don't currently have any liquid electric tape.

 

[joshuabardwell]

I'm not too worried about it, though. Even with half the braid melted through, I would think that the remaining copper should be more than adequate to carry the welding current without excess resistance.

 

[joshuabardwell]

Two layers of heat shrink later...

 

[Shield Arc]

I've always had good luck with this kind of ground clamp.
Tweco Copper Ground Clamp - GC 200