Welding Copper (1 Viewer)

[florida95fzj]

I have a cheap DC flux core only welder and minimal experience welding.

I am trying to weld solid copper wire (electrical ground wire) tied around a 19mm nut. I would like to snake the wire + nut inside an access hole in my frame so I can thread in a bolt from the outside. The problem is I can't seem to get a weld to hold.

Do I need to find steel wire or do you suspect this is just a skill/experience problem?

I started off looking for steel wire but my hardware stores didn't have the right thickness plus flexibility.

 

[AirheadNut]

You’re trying to weld the wire to itself and not to the nut, correct? I would recommend using electrical solder to join the copper to itself.

 

[Malleus]

First of all, you have to understand what welding is: it's not soldering. Welding is melting two pieces of similar material and joining them on a molecular level. You can weld copper, but you have to use a copper electrode.

It's much easier to braze, which is similar to soldering, but done at a higher temperature, and, like soldering, this process can join dissimilar metals. The difference between the result of soldering and brazing is that brazing creates a much stronger bond, because the filler wire is stronger.

 

[florida95fzj]

You’re trying to weld the wire to itself and not to the nut, correct? I would recommend using electrical solder to join the copper to itself.

Correct, I was trying to keep my braid of the wire from unraveling and keep it very tight to withstand the force of the ratchet. My goal was to not damage the nut and keep it strong since it will hold my rear bumper.

You can weld copper, but you have to use a copper electrode.

It's much easier to braze, which is similar to soldering, but at a higher temperature, and this process can join dissimilar metals.

Ok, the welding wire I had was the flux core mild steel type. I was hoping the welding wire would work well enough with copper but no such luck.

Thanks for the advice. I didn't think about electrical solder being strong enough or using the mapp gas torch.

 

[1911]

Silver solder is another option, and quite strong. Indian used silver solder to assemble sheet metal gas and oil tanks.

 

[Waorani]

You can't "weld" copper wire to a steel nut. And you can't weld much of anything with a cheapy flux-core welder. You need to think of something different.

- twist your solid copper tight enough to hold (even then it's likely to bend trying to snake it in)
- tack weld a stiffer steel wire/rod
- etc, etc

 

[e9999]

yup, steel wire, or soldering, or maybe epoxy even. But, steel wire is not that hard to find. I wonder if you could even use a coat hanger for stuff like that.

(as to welding copper to steel, FWIW, I use copper backing to *prevent* steel weld to adhere to it when I'm filling holes etc...)

 

[florida95fzj]

You can't "weld" copper wire to a steel nut. And you can't weld much of anything with a cheapy flux-core welder.

Wasn't trying to weld the copper wire to the nut. The goal was to weld the copper wire to itself to prevent it from unraveling. I went to a small hardware store that didn't have the steel fencing wire I was originally looking for. Had I got the steel fence wire or copper welding wire, it should have worked with similar metals even if not the best method. I don't have any problems doing simple things with the flux core welder.

yup, steel wire, or soldering, or maybe epoxy even. But, steel wire is not that hard to find. I wonder if you could even use a coat hanger for stuff like that.

(as to welding copper to steel, FWIW, I use copper backing to *prevent* steel weld to adhere to it when I'm filling holes etc...)

Yeah, I am going to make the drive to a larger store to get some stronger wire and just solder it. Good to know on your copper trick. I've only ever welded mild steel and nothing more intricate than making brackets. I appreciate the advice here.

 

[Malleus]

FWIW, if you use solder to join the wire, any torque applied to the nut will break the bond. Brazing will not fail like solder will.

 

[Malleus]

absolutely no affiliation, just a quick googling:

 

[florida95fzj]

FWIW, if you use solder to join the wire, any torque applied to the nut will break the bond. Brazing will not fail like solder will.

Thanks, I was going to look into different types of solder to see if there was something stronger than what I use for DC wiring. It didn't seem feasible to me unless higher temps + a different type of solder was the answer. I have your average $80 mapp gas torch with an adjustable flame control but not the more expensive brazing set, for whatever that does. I'll look into this and see what I can do with what I have.

 

[Malleus]

What you have will work. Look up the Handy & Harmon Brazing Handbook. It'll tell you everything you need to know. I've had my copy for 40 years.

 

[florida95fzj]

What you have will work. Look up the Handy & Harmon Brazing Handbook. It'll tell you everything you need to know. I've had my copy for 40 years.

Great. Thanks for the link to that book!

 

[Malleus]

The American Welding Society (AWS) copied it and sells it for a ridiculous $160. Handy & Harmon gave it out for free.

 

[e9999]

Yup, brazing is an amazing process with pretty small entry challenge. Really worth knowing about and practicing.

 

[florida95fzj]

Yup, brazing is an amazing process with pretty small entry challenge. Really worth knowing about and practicing.

Yeah, I am glad I am learning more about this. At least the factory weld that broke free the nut inside my frame wasn't something catastrophic and I have some time to get it right.

 

[Waorani]

I think you've led yourself down a rabbit hole with the whole welding idea. Yes it is possible to weld copper but you're talking TIG machine, helium gas and the skill to use it.

 

[florida95fzj]

I think you've led yourself down a rabbit hole with the whole welding idea. Yes it is possible to weld copper but you're talking TIG machine, helium gas and the skill to use it.

Yeah, the copper wire was just because it was all I could get at a small town hardware store. It's not a necessary part of getting this done.

I tried just twisting a coat hanger like in your picture but it didn't hold. Not sure if it has to due with the size (19mm) or some other reason. That's when I started to think of ways to fasten it better.

 

[e9999]

did you try welding the coat hanger to the nut? Or you could weld a nail or screw or bolt to the nut and then use something to hold or attach the nail etc. I've done this once before with a strip of sheet metal too.

 

[pb4ugo]

I had the same issue of stripped or missing threads in a blind hole in the frame as the op. I found a piece of tubing with the proper id and drilled and tapped it, then drilled a hole in the frame to the tubes od. I beveled the end of the tubes' od for weld bead. I used a bolt and threaded into the new threads to hold the tube in place and inserted into the frame. Once welded, I ground the welds flush. In the past, I've also welded nuts to scab plates and slid them inside the frame too. Last resort would be rivnuts, but their retention would be questionable.