# Resistance Soldering - HELP!



## Matt Vogt (Jan 2, 2008)

Okay, so I am building a resistance soldering machine, according to the pdf that someone posted here ( I can't find it using the search engine, please let me know if the poster is reading this).
If you are not familiar with it, the pdf shows how to build a unit from a battery charger. I have pretty much finished it, except for working out the details on the tweezers / probes. 
I cannot find any carbon tips around this area, so I am trying to use tungsten. I _assumed _that any conductor that would not stick to the object would work, since American Beauty tweezers use stainless tips. So I fashioned a handle out of oak that would work well (springy) for tweezers, drilled the holes for the electrodes, got all excited that I am finally close to completion after months of planning to build one.....and nothing. I tried to solder a brass part onto another piece of brass, I get an arc, some heat, but no solder transfer. I have used up to probably about 8 amps trying to get something to work. 
PLEASE let me know if you have any suggestions. I have been off work most of the last year, so I would rather not pay~$43 for the replacement tips from American Beauty if there is an alternative.
Thanks for the help, Matt


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## Rod Fearnley (Jan 2, 2008)

For a source of carbon rods, take a standard flashlight battery apart, and you will find the centre rod is carbon. Use an old pencil sharpener to form a point.
Rod F.


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## Dwight Ennis (Jan 2, 2008)

I think Micro-Mark sells carbon tips as well. So does PBL for their unit.


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## Matt Vogt (Jan 2, 2008)

Thanks, gents for your quick replies. So it is your opinion that it needs to be carbon? I actually took apart a AAA battery last night - only size I could find at home that was carbon, but the carbon was so small, and I thought it wouldn't matter so I tried the tungsten.


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## peter bunce (Dec 29, 2007)

Hi Matt, 

What you want are carbon electrode rods; they are 2" long and copper coated. Got to a welding supply shop and ask them for some, or where can you buy some. The can be a bit fragile, the copper coat will add some extra strength


Rod is correct in that traditional batteries ghave at their center a carbon rod but they are not copper coated and can be messy to get out and naturally are short in length. 












Ebay sell them - here is a photo - of Ebay who did have some so you can see what they look like, the seller is in the UK and the offer has now closed anyway. They can also have a point like a sharpened pencil


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## xo18thfa (Jan 2, 2008)

Is the purpose for using carbon rods to produce a resistance, hence the build up of heat? These machines look worthwhile. Like to here how it turns out.

Bob


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## Dean Whipple (Jan 2, 2008)

Matt, 
This is probably the link you were referring to, the link to the PDF resistance soldering article is half way down the page....


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## armorsmith (Jun 1, 2008)

Matt, 

Try this link, or Google "resistance soldering units". 

http://www.google.com/url?sa=t&sour...x8WgAg&usg=AFQjCNEC9d3xCIHbYBaBTOpIJGoDpc7GNQ 

or 

http://www.trainweb.org/bristol-s-gauge/Projects/rsu.html 

Bob C.


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## SteveC (Jan 2, 2008)

Is the purpose for using carbon rods to produce a resistance, hence the build up of heat? These machines look worthwhile. Bob

While the following PDF isn't on the type of equipment being referenced it does give a good explanation. While the article doesn't explicitly state it, my understanding of the use of graphite (i.e. the carbon rods) electrodes is that while they are very efficient conductors of electricity, they are also very poor conductors thermal energy.

Resistance Brazing Basics[/b]


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## Greg Elmassian (Jan 3, 2008)

That also jives with using stainless steel, it is likewise a poor conductor of heat. 

Regards, Greg


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## DTI356 (Jan 3, 2008)

Matt, 

You didn't say this so I'm going to ask......did you use liquid flux in the joint you were trying to solder?


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## Matt Vogt (Jan 2, 2008)

Thank you everyone for the input. 
Steve, what you say about thermal energy makes sense. I have no idea what tungsten's thermal properties are, but do you think that there would be enough of a difference to not melt any solder at all? The only time I had ANY solder melt was when I placed the solder between the electrode and the brass to make sure I even had a complete circuit. Yes, I realize this is not the way to solder - it was just an experiment. Of course, the solder simple splattered - vaporized. 
No, Brian, I didn't get that far. I was using rosin core solder. I'm sure liquid flux would be better. I probably will if I get this to work. 

I should probably point out that I am using a foot pedal and router variable speed dial to control the output. 

Thanks again


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## SteveC (Jan 2, 2008)

Matt

By no means am I an expert in this, however, based on my understanding of incandescent lamps which for the most part all use tungsten filaments. When cold (i.e. open circuit, lamp off) the filament has a very low resistance (darn close to a dead short), but when the circuit is closed and the current starts to flow and the filament starts to heat the resistance very rapidly increases. This continues until the filament is caused to become incandescent and the resistance and current flow stabilize. To get an idea of just how quickly this occurs, just think about how long it takes an incandescent lamp to light after you flip the switch.

The above described characteristic of tungsten is exactly what you don't want, because you want the concentration of thermal energy (i.e. heat) to take place in the pathway taken by the current flow between the two electrodes in the metal that you're trying to solder to. Not to be partially dissipated in each of the electrodes.

I don't know if you've ever had the experience of seeing just how long it takes a 1/2" box end wrench to turn red hot and melt. When it accidentally falls and lands across the terminals of a high amperage deep-discharge marine battery, but I can tell you it doesn't take very long at all. And that is what you are doing when using a resistance soldering unit, just in a more controlled manner.


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## SE18 (Feb 21, 2008)

I have that pdf and it is awaiting time to be built behind many other projects. 

I plan to use an old MTH transformer (which the article states you can use in place of the auto charger, I think they mention ZW). 

I think that one of the advantages of the unit is the ability to rapidly heat an area and then the device you are working with turns cold, unlike a soldering iron that stays hot. 

I have some old wood film tweezers (used to process photos) that I may use in building that device.


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## Dean Whipple (Jan 2, 2008)

Matt, 
Ooops I forgot to put in the link















This is probably the link you were referring to, the link to the PDF resistance soldering article is half way down the page.... 
*Soldering track jumpers.... *


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## xo18thfa (Jan 2, 2008)

Posted By SteveC on 25 Jan 2010 05:27 PM 
Is the purpose for using carbon rods to produce a resistance, hence the build up of heat? These machines look worthwhile. Bob

While the following PDF isn't on the type of equipment being referenced it does give a good explanation. While the article doesn't explicitly state it, my understanding of the use of graphite (i.e. the carbon rods) electrodes is that while they are very efficient conductors of electricity, they are also very poor conductors thermal energy.

Resistance Brazing Basics[/b]


That answers it. Thanks


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## xo18thfa (Jan 2, 2008)

Posted By Greg Elmassian on 25 Jan 2010 07:43 PM 
That also jives with using stainless steel, it is likewise a poor conductor of heat. 

Regards, Greg 
I did not know that. I was wondering why Matt said stainless steel tweezers. Learn something everyday.

Bob


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## maculsay (Jan 2, 2008)

Posted By Matt Vogt on 25 Jan 2010 09:35 PM 
Thank you everyone for the input. 
Steve, what you say about thermal energy makes sense. I have no idea what tungsten's thermal properties are, but do you think that there would be enough of a difference to not melt any solder at all? The only time I had ANY solder melt was when I placed the solder between the electrode and the brass to make sure I even had a complete circuit. Yes, I realize this is not the way to solder - it was just an experiment. Of course, the solder simple splattered - vaporized. 
No, Brian, I didn't get that far. I was using rosin core solder. I'm sure liquid flux would be better. I probably will if I get this to work. 

I should probably point out that I am using a foot pedal and router variable speed dial to control the output. 

Thanks again Matt...re-read Peter Bunce's response to you. Using copper coated carbon electrodes is what I use with the resistence soldering unit I built (see in tools forum archive). I couldn't find just a few, so I bought the whole box from my local welding store, which will last me into the next millenium or two. So if you can't find them locally, I'll be glad to send you a small supply if you spring for the shipping costs. Just send me your mailing address via MLS email and I'll get some into the mail to you.


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## Matt Vogt (Jan 2, 2008)

Thanks again, everyone for the great advice and links - I've looked into all of them.

Bob, I looked on ebay for the rods that Peter was talking about, and there aren't any right now. There is a welding supplier about 20 minutes from here, but they did not carry any. I'm not aware of any other local suppliers, so I would _greatly_ appreciate it if you could send several. I will email you my info, along with a check as soon as I get your address.


I have let other projects (like a failing leech field) take precedence over trains lately, but I am always amazed at the helpfu, courteous people here. 


Take care everyone - this is a great community!


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## armorsmith (Jun 1, 2008)

Matt, 

I don't follow the difficulty of using tungston for your resistance rig. A friend has one he has used for years to build On2 models using tungston and it works great. Tungston is also used in TIG welding, and I am sure if the heat was being absorbed in the tungston electrode it would not work well. I am not sure what size tungston you are using, but the one I reference is only about .030 diameter. Don't give up on the tungston, I am sure from experience it will work, however I don't remember what the amperage of his rig is. 

Bob C.


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## SteveC (Jan 2, 2008)

Bob

I don't think you can equate any type of arc welding to resistance soldering/brazing. While both processes use the flow of electrical current (i.e. both AC & DC (i.e. in both polarity configurations)), the manner in which the flow is used is quite different.

In one you're using the arc created by the gap to develop the heat to melt both parent and filler metal to form one continuous piece, when cooled.

In the other you're merely creating a short path in the parent metal for the current to flow, and relying on the native resistance of the parent metal to this flow to cause the metal to heat to a temperature high enough that the interface metal (i.e. solder/brazing alloy (differentiated mainly by temperature range)) will melt and wet both surfaces to be joined, and when cooled results in a strong bond between the pieces.

I'm not saying that tungsten can't be made to work, however, based on the characteristics of tungsten that I am aware of and have stated above, it wouldn't seem to be the best choice. The transformer that Matt has to work with may not be capable supplying enough amperage to make the tungsten electrodes work.


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## SE18 (Feb 21, 2008)

For a beginner it's so confusing, all the choices out there: 

Pencil soldering iron 
Gun soldering (like the ubiquitous Weller) 
Resistance soldering (many types) 
Brazing 
Soldering pencil powered by torch 
Small butane torch 

What's a body to do?


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## SteveC (Jan 2, 2008)

What's a body to do? Dave

I would say that the thing to do, is recognize that each of the items you've listed has its very own place and purpose for which it was designed. Thus, when presented with a given circumstance matching the proper tool to the job at hand, it will excel and accomplish the task better than any other.


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## RimfireJim (Mar 25, 2009)

Posted By SteveC on 27 Jan 2010 08:31 AM 
What's a body to do? Dave

I would say that the thing to do, is recognize that each of the items you've listed has its very own place and purpose for which it was designed. Thus, when presented with a given circumstance matching the proper tool to the job at hand, it will excel and accomplish the task better than any other.









Exactly! It's like having a lot of different kinds of hammers. Each one has a specific use. You don't use a sledge hammer to drive in a tack, you don't use a claw hammer to form a rivet head, etc.

I have an adjustable temp soldering station with a pencil iron with interchangeable tips that I use for electronics and fine wiring work.
I have a soldering gun that I use for the occasional electric motor and household appliance repair.
I have a huge soldering iron (lots o'mass but not high wattage) that I use for soldering things that would suck the heat out of something smaller, like battery cables and copper flashing.
I have a MAPP gas torch I use for soldering copper pipe. Used to use a common propane torch, but it doesn't put out enough heat for 1" copper.

I have a pencil butane torch that seemed cool but I haven't used yet.
I have a micro oxy-acetylene torch that I've used for silver soldering a few delicate things.

I have a standard oxy-acetylene torch set that I use for brazing, welding and cutting.


I probably have just as many different hammers. Oh, did I say I was a tool nut?


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## Semper Vaporo (Jan 2, 2008)

Posted By RimfireJim on 29 Jan 2010 07:32 PM 
Posted By SteveC on 27 Jan 2010 08:31 AM 
What's a body to do? Dave

I would say that the thing to do, is recognize that each of the items you've listed has its very own place and purpose for which it was designed. Thus, when presented with a given circumstance matching the proper tool to the job at hand, it will excel and accomplish the task better than any other.









Exactly! It's like having a lot of different kinds of hammers. Each one has a specific use. You don't use a sledge hammer to drive in a tack, you don't use a claw hammer to form a rivet head, etc.


Whilst I agree with you in principle... there are those that espouse... "Any tool can be the right tool." and "To the man with a hammer, everything looks like a nail."


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## SteveC (Jan 2, 2008)

Thus there's always conflict.









Perspective[/b]


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## FH&PB (Jan 2, 2008)

Stainless doesn't work (I suspect) because it conducts electricity too well. What you want is something that _sort of _ conducts, like carbon or tungsten. (That's why you stick the copper-plated carbon rods in a pencil sharpener, so the copper doesn't contact the work and just make a short circuit.) 

You should be able to get a box of carbon rods on the net from someplace like MSC or Grainger - they're more than you need, but cheap enough to be worth it. Or you can get PBL tungsten tips from hobby shops (I got some from Caboose Hobbies, who are on the net, too). 

Other questions? I'll answer as I can.


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## Jack - Freshwater Models (Feb 17, 2008)

Matt,

Try your local welding supply for copper clad carbon electrodes. I use 3/16" or 1/4" electrodes. Tweezers are OK and I have some but seldom use them.

What voltage/amperage is your transformer? 

Jack


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## hawkeye2 (Jan 6, 2008)

Ask for Arcair rods at your welding supply store. They are copper clad carbon rods that are used with an arc welder and compressed air source for gouging, removing welds and so on. They come in various diameters and rectangular sizes too. You will have to cut them to the length you want and reshape the ends too but that isn't a difficult task. I have never tried to buy small quantities but I doubt you can buy less than a box which would be two lifetime supplies. They are consumed rapidly in the process of removing welds etc. and are rarely used in the home workshop so there probably isn't any reason for them to be offered in small packages like welding rods are. You might be able to find a welding/repair shop that has some and might sell or give you a few. The welding supply store should be able to help you locate somebody there.


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## Matt Vogt (Jan 2, 2008)

UPDATE:




Howard Maculsay was kind enough to send me some for paying shipping - thanks again, Howard!

I hadn't had time in the last couple of weeks - due to too many 1:1 projects getting in the way. However, I couldn't wait any longer, and decided to at least find out if this thing is going to work.
I made a crudely formed wooden handle (pic to follow soon) to hold the electrodes, crimped wire terminals on the ends of the rods, and tried it. Let me preface by saying that because I was in a hurry, I did everything incorrectly: I didn't clean the brass, used pipe fitter's flux with a q-tip, etc. 
However, that didn't seem to matter! I soldered to roughly 1" sq pieces of scrap brass together with no problem, in about 3-4 seconds! WAHOOOO!







It worked just as I had hoped. I have yet to try it on a piece that has another piece soldered near it, but will soon.
I am newly encouraged, and hope to refine everything a bit in the next week. I'll post pics and give you a rough idea of what I did, and how to do it better yourself...In the mean time, if you have any questions, please feel free to ask!
Thanks again for all of your comments/helpful suggestions!

Take care,
Matt


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## SteveC (Jan 2, 2008)

Matt

Thanks for taking the time to let us know how things have worked out for you, and definitely it's good to hear that you got it working.


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