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Discussion Starter #1
Hi. My name is Patrice Lemée and I am a metal sculptor.

I need help with resistance soldering and this seemed like a good place to ask. It’s hard to find people using this and I think you guys do. It’s not about trains so I hope it is still ok to ask. Let me know if it’s not.

I have purchased a soldering unit from American Beauty. Very happy with it so far but I am having a small problem. Well I hope it’s small. :( I am trying to solder a small piece to a much larger piece as you can see in this picture.



The thing is I need to put a lot of heat into the larger piece for the solder to properly flow to it. The result is a perfect solder joint but the carbon electrodes leave marks. Since I am doing this on a near finished sculpture and in hard to reach places I need to minimize this scarring of the surface. Not sure how to do that or if it’s even possible. These are carbon electrodes and they glow red hot from heat, more damage from the electrode e that glows more and also a little powdery residue on it afterwards.

Not sure if I explain myself well or if anyone here has an idea of how to do this better but I am taking a chance and would be very grateful for any help. Or of course if anyone knows of a better place to find info on this that would be great.

Here is my latest sculpture and the small feet are what I am working toward soldering.



Thanks for you help.
 

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it may be necessary to use a 'sacrificial' piece under the electrode, to reduce the scorch marks , or a larger electrode that will increase the area of contact, and reduce the number of amps per square inch
 

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Discussion Starter #5
John, I can't do that but I may have to live with the marks and incorporate them in the design if I can't get rid of them completely.

WCGCA, that is an interesting idea but I have no idea how I would implement it since it usually is on a curved surface and a bit cramped. But I'll look into it some more for sure.

Flyboy, you are very kind, thanks.

And a big thanks for the help guys, I'll post more if I get better results.
 

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It's quite possible that soldering on a finished piece simply isn't in the cards. I do wonder about the glowing electrodes, perhaps the excessive heat at the spot is the problem. Resistance soldering is supposed to heat the workpiece, not the tool. I've only used one resistance soldering rig, it was hand made. However, we had no red hot electrodes.

Have you considered low temperature solder for the critical pieces? Another option might be brazing or soldering with a torch, you don't get contact scoring with that method.
 

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Discussion Starter #9
I'll make it work John, even if like I said it means a little scoring that in the end I might be the only one that notices it. The drawback of being a tad perfectionist (ok maybe more than a tad ;) )

The red glowing is really just because I am dumping a lot of heat it doesn't happen until late in the process. Pulsing it might help too, got to try that some more.

I did not mention it but brazing would mean OA or Oxy-Propane and I can't have that because of insurance since my shop is attached to the house. That's why I am pursuing electricity based solutions. The solder I use is a low temp one for silver solder that is. About 435F if I remember right, not sure they make lower than that in silver which I like because it stays bright. (This one is named Stay-Brite after all :D)

Thanks again for your help.
 

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That's pretty good for silver solder. Dumb question. Why not use a large soldering gun like the Weller D650, it's a 300W model and will do significant soldering on large pieces. Resistance soldering may not be ideal for the work you're doing. You won't have any discoloration due to excessive temperatures at the contact point.
 

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Discussion Starter #12
I do have one of those John and will give it a try. Now sure though that the 300W will be enough for that large a heat sink but it's worth a try, thanks.
 

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for a little more heat on the 300 watt iron, replace the tip with a piece of ordinary house wall wiring, in 14 or 12 gauge ... they make excellent tips, and the cost is very low .. solid copper wire ..
 

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Discussion Starter #16
WVGCA, I tried a lower setting and get some glowing almost instantly. I am troubleshooting that with the company I bought the machine from. Not sure what is happening.

John, I was wrong the Weller I have is the 140W model. I still tried it and definitely doesn't put out enough heat. I'll will try and make the resistance machine work before I buy that 300W to try. Gotta justify that 2500$ price tag. ;)
 

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Discussion Starter #18
Oh no John I meant for my resistance soldering machine. It's from American Beauty. Got 2 handpieces with a few extra tips. Add shipping, taxes and duties.
 

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the Weller, if it's the same as the one i got, is 100 watt low, and 140 watt high ...
the household wiring thing works great .. it -may- be enough , easy to try it out ??
 
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