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Thread: Soldering steel FYI

  1. #41
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    Quote Originally Posted by goodsteel View Post
    I called Kester solder co. today and asked to speak to someone who can answer my questions about solder thickness, and meathods for soldering steel. I was told that Peter Bianca is the man I needed to talk to, and was given his phone number.
    He told me that the ideal thickness of the solder is in the tens microns. Basically, as close as you can get the two pieces together is where it needs to be.
    The reason for this, he explained, is that the solder is changed on the molecular level where it is bonded to the steel. It actually takes some of the elements from the steel into itself, and deposites some of itself into the steel. The result is that the metal that is doing the bonding is no longer the same stuff that you melted onto the opposing surfaces. The tensile strength of the joint is much stronger than the solder itself because of what it gets from the steel. The bigger the gap between the two pieces, the weaker the joint will be. The only thing that throws a monkey in the wrench here, is that you have to have good contact with the parts you are bonding and if your parts don't fit worth a darn, then you need a thicker bond line in order to get anything to stick in the first place other than a few tiny points of contact.
    Basically, once again we see that fit is king.
    He went into a whole tutorial about fluxing and tinning and I described my trick to him, which he agreed was a very good way to force a good bond quickly, and all he added was a caution to stick the two parts together within minutes of tinning them.
    All in all, a very informative discussion!!!
    I read that very same information years ago which included silver soldering and also brazing. Lots of good info here for people that haven't done it the correct way previously.
    Last edited by LynC2; 09-09-2013 at 07:34 PM. Reason: typo
    NRA Endowment member, TSRA Life member, Distinguished Rifleman, Viet Nam Vet

  2. #42
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    All very good info but I would like to address a common misconception about soldering and hot bluing, it is sometimes stated that the solder will not take the heat of bluing but heat is not the problem and no solder (except maybe some of the very low temp low strength solders) is "melted" out because of the heat of the bluing bath. Rather some solder joints will fail in a hot blue bath because it is chemically attacked by the caustic solution and this happens waaaay before melting temperature of most solder joints is reached! The point is that if a joint is to be hot blued then the solder alloy should be chosen by the resistance properties of the alloy not the melting point since the wrong alloy will be chemically attacked and will still fail regardless of melting point.

  3. #43
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    Quote Originally Posted by oldred View Post
    All very good info but I would like to address a common misconception about soldering and hot bluing, it is sometimes stated that the solder will not take the heat of bluing but heat is not the problem and no solder (except maybe some of the very low temp low strength solders) is "melted" out because of the heat of the bluing bath. Rather some solder joints will fail in a hot blue bath because it is chemically attacked by the caustic solution and this happens waaaay before melting temperature of most solder joints is reached! The point is that if a joint is to be hot blued then the solder alloy should be chosen by the resistance properties of the alloy not the melting point since the wrong alloy will be chemically attacked and will still fail regardless of melting point.
    Right on, the caustic properties of a hot blue tank will dissolve soft solder like a Democrat passing a new tax bill!
    NRA Endowment member, TSRA Life member, Distinguished Rifleman, Viet Nam Vet

  4. #44
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    A silver braze alloy requires capillary action to distribute the brazing filler metal throughout the joint interface. For Capillary action to work effectively the clearance needs to be 0.001"- to 0.005" with 0.001"- to 0.003" preferred and 0.0015 the strongest.

    "The joint strength is affected by the joint gap. Joints made with smaller gaps are more dependent on that inter-atomic strength. But there must be a gap into which the silver solder can flow." http://www.cupalloys.co.uk/best_practice/

    "Note that the strongest joint (135,000 lb/in.2 [930.8 MPa]) is achieved when the joint clearance is 0.0015 in. (0.038 mm). When the clearance is narrower, it is difficult for the filler metal to distribute itself adequately throughout the entire joint, reducing joint strength. Conversely, if the joint clearance is wider than necessary, the strength of the joint will be reduced almost to that of the filler metal itself." http://www.aws.org/wj/amwelder/9-00/fundamentals.html


    http://www.lucasmilhaupt.com/en-US/b...zingprocedure/
    Last edited by M-Tecs; 09-10-2013 at 10:19 AM.

  5. #45
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    That's the original article that I remember reading. I wonder if there is a difference between solder and brazing alloy.
    I did read this in that article:
    .....if you are joining two flat parts, you can simply rest one on top of the other. The metal-to-metal contact is all the clearance you will usually need, since the average "mill finish" of metals provides enough surface roughness to create capillary "paths" for the flow of molten filler metal.
    Precision in the wrong place is only a placebo.

  6. #46
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    Quote Originally Posted by goodsteel View Post
    I wonder if there is a difference between solder and brazing alloy.
    Way back in Tool & Die tech school in 1978 and 1979 we were taught that solder was purely a surface bond and that brazing was a surface and an alloying process that was a couple of microns thick into the base metal. Welding was melting the base metal and inducing a filler metal.

    Today's standards claim solder is a process under 840 degrees and brazing is above 840 degrees however this doesn't fit for plastic welding and welding of low temp items like lead and tin.

    http://www.tinmantech.com/html/faq__...dering__te.php

    http://www.silfos.com/htmdocs/product_support/faq.html

    Back to silver soldering/brazing. Since 1978 I have done thousands of silver solder joints. The only failures have been when the clearance has been too thin to allow capillary action to allow the alloy to fully cover the joint area. There was a time period that I was used silver solder ribbon and sheet in a heat treat oven. On machined surfaces if I clamped too tight the clamping force would overcome the capillary action and I had failures with some to those joints. My solution was to either machine .002" clearance areas or to use a prick punch and light clamping force.
    Last edited by M-Tecs; 09-10-2013 at 12:43 PM.

  7. #47
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    Goodsteel, for a banded front sight, how to you TIN the front of the barrel without getting solder over areas you dont want to get tinned? Do you just "rough" up the inside, and leave a "buffer" of untouched barrel?

    The question is equally as valid for a rear sight of defined area. You want the tinning where the sight is, but not elsewhere. how to control that?

    I'd think that if you cold blued the area around the sight (ala midway youtube vid) or colored it in with a pencil so the solder beads off, that as soon as you rubbed the area with steel woll, you'd break the protective layer and you'd be right back to tinning outside the sight area?

  8. #48
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    I just solder them on, file off the little excess, polish it, then run it through the bluing tanks.
    If you are trying to sweat some sights onto a blued barrel without destroying the bluing, then you are going to have to be very careful when tinning the barrel and the sights if you want it to look decent.
    Outline the sight with pencil, and use a 1/4" stone to polish off the bluing about 1/16" inside the line. Heat it up and roll your steel wool onto tight ball. flux the bare spot and melt just the tiniest dab of solder onto the bare steel. Rub it in staying well away from the edges. Just try to feather it out from the center till you get the spot mostly covered. Repeat this process with the sight that you are trying to stick down. Clamp them together in the correct location with more flux and heat 'em up till they wash.
    I have heard that solder paste would be ideal in this situation, but I have yet to try it.
    Precision in the wrong place is only a placebo.

  9. #49
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    you just solder them on... so you pre-tin as normal, and just indiscriminately tin outside the sight area?

    This is a barrel in the white.

  10. #50
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    Exactly. I'm not out to waste solder or anything, but If the barrel is in the white, then I'm focused on getting a good joint.
    If I get outside the line some, I don't worry about it because I can always polish it off later.
    Not saying that's the end all be all way, but its a way that works for me.
    Precision in the wrong place is only a placebo.

  11. #51
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    cool. So, looking at how you tin, the layer ends up VERY VERY thin. How do you clean that up around a barrel? a banded sight has some tight nooks to get into to clean out tinned solder.

  12. #52
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    Needle files, dental picks, and stones have worked for me so far.
    Here's a banded sight I made for my shotgun. I silver soldered it first (this was before I found out about the scrubbing trick) and had quite a bit of overrun.
    Attachment 81740
    But as you can see, the files don't give a rip what it looked like before.
    Attachment 81741
    And neither did the shotgun (in this case, only the band is attached. The ramp has no solder under it)
    Attachment 81742

    Also, I would like to add that I believe the fit of the parts dictate how thin the joint is. I always tin both surfaces, so that I am for darn sure that the solder even stuck to them, then I put them together, and heat them up. Once they are hot, I touch the solder wire to the joint opposite the side it's being heated from, and make sure it has all has all it wants.

    The only time I have had a joint fail was on a gun I repaired, and the parts didn't fit together well enough to give a good joint. I should have known better and should have followed my gut, but I thought "this is the right way to do this, and I'm using the right solder". I found out, I can say that to myself all I want, but it's a little hard to say the same words to a client. I repaired it for free, and took it as a cheap lesson in soldering.
    Last edited by MBTcustom; 09-13-2013 at 04:27 PM.
    Precision in the wrong place is only a placebo.

  13. #53
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    Good thread Tim! I've been having a hard time soldering steel to steel here on the farm. My FIL started body work back in the days of hot lead and files and he could always get a good bond that I couldn't. So I generally cheated and used Brownells silver solder paste/flux, great stuff but crazy expensive last I looked. Using standard No-Korode flux or muriatic acid hasn't worked great for me with 50/50 or silver. I think your steel wool trick might be the fix.

    BTW- to keep the solder from sticking where it's not wanted I believe you can use common chalk to keep it from sticking. I think old Clyde Baker or maybe Vickery gave me that hint. And I also remember the old timers talking about using a type writer eraser to clean up prior to soldering. I bet a cratex polishing bob would work, what with type writers getting pretty rare these days.

  14. #54
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    do you plan on using hi-force 44 solder on your 500 jeff build? Or do you plan on moving up to a hard solder with an oxy-fuel torch? The price difference is heavy between a 96/4 silver solder and something with a higher tensile strength.

  15. #55
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    I've got several options here, but it will really depend on the fit of the quarter rib. If it fits perfectly, then i may consider HF44, but to be honest, Im probably going to use this Sn96.5 Ag3.0 Cu.5 solder, or the 15%Ag. Im still doing research, but I don't want to induce anymore heat into the barrel than necessary.
    Precision in the wrong place is only a placebo.

  16. #56
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    that is very clear. I will try silvalloy from Brownells. solder temp is kinda high at 1100ish, but youtube assures me I can use a propane torch to get the heat up, though I dunno...

    hopefully a MAPP gas torch can do it or I can find a buddy with an oxyfuel setup.

  17. #57
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    You might have better luck than I did, but I tried to silver solder with propane, and it sucked rocks on anything but thin metal. Next, I bought the best MAP gas torch I could find (almost $100) gauranteed to burn hotter than the hinges of hell and damnation LOL!
    Again, it got me closer, but not to where the solder would follow the sultry sound of my voice.
    Finally, I got on Craigslist and searched till I found a HVAC feller that was retiring, and I bought his little portable torch.
    I'm here to tell ya! That'll make the 'ol eyebrow peek out over the 'ol brazing goggles!

    Nothing beats the shear power of the oxy/acetylene torch. It's head and shoulders hotter than either of the other two options.
    Also, if you get the little set, you don't need to sign a contract for the bottles, and the exchanges are very reasonable (albeit frequent).
    These little rigs can be had for less than $150 and can be found in pawnshops all over. They're just the right size for the gunsmith IMHO.

    Hey WR, are you local to me by any chance? I'd help you out if by some miracle you were close to central Ar?
    Last edited by MBTcustom; 11-01-2013 at 04:26 PM.
    Precision in the wrong place is only a placebo.

  18. #58
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    Stuck in CA, with nothing but more CA for 4-6 hours in every direction. I'd love to get personal help on these things, but the best I can do is community college courses (great for welding, not good for gunsmithing) and pinging the experts here. Then just hope I don't muck up too bad.

    Lots of practice on scrap.

    MAPP is too cheap not to try, as long as I don't burn more than 12 inches or so of solder trying to get it right. A buddy might be inheriting oxyfuel from his Grandfather and will be able to help if that is the case. Otherwise, it's as you say. Hit Craigslist or any source I can and try to find a small set of oxyfuel.

  19. #59
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    Quote Originally Posted by goodsteel View Post
    Next, I bought the best MAP gas torch I could find (almost $100) gauranteed to burn hotter than the hinges of hell and damnation LOL! Again, it got me closer, but not to where the solder would follow the sultry sound of my voice.

    MAPP was a viable option for silver soldering once and it still has the reputation of, as you so colorfully put it, "burning hotter than the hinges of hell and damnation" but unfortunately that's no longer true as you found out. Unfortunately what is being called MAPP these days is little more than propane, basically just a sales gimmick based on the reputation of a product that's no longer available. No MAPP has been produced since 2008 and it had been getting scarce even before that, MAPP is just a licensed trademarked brand name now for Propylene or a Propylene/Propane mix and is not nearly as hot as it once was. You are correct about Oxy/Acetylene being the best of the best and it even allows the option of actually welding steel (sometimes even being called a "poor man's TIG") but even Propane, Propylene or what passes for MAPP these days are just fine for silver soldering and are much easier (and cheaper) to get than Acetylene plus any of them are a LOT safer! The trick to using any of these gases is using Oxygen with an Oxy/fuel set-up, basically just an Acetylene welding/cutting rig with the proper tips for the gas being used but those cheap little fuel/air torches like the common one tank Propane rigs sold just about everywhere or the phony MAPP one tank rigs are mostly going to be an exercise in frustration for the purpose being discussed here! Add that Oxygen tank and all that changes, you still can't weld steel with these rigs but silver soldering then becomes easy.

  20. #60
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    Quote Originally Posted by goodsteel View Post
    snip
    Nothing beats the shear power of the oxy/acetylene torch. It's head and shoulders hotter than either of the other two options.
    Also, if you get the little set, you don't need to sign a contract for the bottles, and the exchanges are very reasonable (albeit frequent).
    These little rigs can be had for less than $150 and can be found in pawnshops all over. They're just the right size for the gunsmith IMHO.

    Hey WR, are you local to me by any chance? I'd help you out if by some miracle you were close to central Ar?
    Oxy/acetylene - I do love the old fire axe......
    One mechanic here loved it so much his nickname was "Hot wrench"....
    Go now and pour yourself a hot one...

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