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  • Silver Solder?

    I've been able to do 2.25"x 8tpi internal threads before on my 11" Logan for cast iron backplates, but man, they were a bear. You guys eventually got me thru it, but now I'm wanting some internal 1"x8 tpi which I'm thinking is even harder. The 1" boring bar that got me thru before ain't gonna fit for one thing. So I thought of a way to cheat.

    Since 1"x8 tpi is a standard thread I got a me plain old zinc nut and turned it down to fit into a pocket in the part I want the threads in. Here's a pic of both parts.



    And here's a pic of them together.



    I'm thinking silver solder would be a nice clean way to attach them, but since I've never done that before how would I know?

    The bigger part is 1018, 2.125" in dia, and the threads are whatever they make standard zinc plated nuts out of.

    I have a OA torch. Propane is also an option. I could very easily be persuaded into buying a hot plate if that would work. Experience wise I've soldered copper pipe and electrical stuff. Soldered lugs on a long set of battery cables once with the OA.

    Any advice on silver solder methods and materials, or alternative attachment methods is welcome. There's a distinct possibilty this is another one of my crackpot ideas, and, if that's the case, I'd appreciate knowing that!

    Thanx for any help.

    SP

  • #2
    Personally, I would smear some Loctite 609 retaining compound on it and call it a day.

    http://www.henkelna.com/cps/rde/xchg...UID=0000000HWO

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    • #3
      I've done a similar operation, but sweating a sleeve on a larger diameter that I'd ruined by turning undersize. My first try with brazing compound didn't work well because the stuff didn't wick into the crack well and I couldn't get the whole thing up to heat at the same time.

      I got some silver solder with a high flow rating and it worked great. Fed in at the top it just showed as a bright line at the mating surface at the bottom. I think you can get your job done just fine.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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      • #4
        Use the right flux and the right solder and it's a piece of cake. My biggest problem is that I always overheat the workpiece.

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        • #5
          Originally posted by snowman
          My biggest problem is that I always overheat the workpiece.
          Aint it the truth!! I can braze, oxy-weld, wire weld, stick weld, etc etc but I cannot get silver soldering down -- for this very same reason ... too much heat!!!
          If everything seems to be going well, you have obviously overlooked something........

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          • #6
            I wonder if one of all'a y'all could clear up the silver solder mystery for me. I've used silver solder in electronics but I've come to understand that is not the same thing as what is used in machinery circles, that being I've known as brazing with brass and flux. Some of the confusion may come from reading descriptions from foreign countries regarding the process.

            So is silver solder in this application at all like brazing or is it more like soldering copper pipe? If you don't ask the stupid questions you stay stupid!

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            • #7
              Well I've been messin' around with whatever I had on hand. I know it's "some" kind of silver solder and I'm using the flux I had leftover from copper piping my air lines, but so far ... it ain't working!

              It seems like the flux is all burnt and gone before the solder ever melts. I started with the propane but it didn't seem to have enough capacity to get the whole part hot. Then I went to the OA but I think it was already too late.

              Just to experiment I cleaned up some scrap and had a fresh shot with the OA, but I think l'm violating the right flux right solder law Snowman mentioned.

              Loctite 609's looking better and better .... lol.

              SP

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              • #8
                In electronics, what they call silver solder is silver bearing solder. It's stronger than regular solder and takes a bit more heat to do, but it's still soldering.

                Silver soldering is brazing basically, and takes much more heat to do. It's also a lot stronger. There are many alloys available- one that I use, because it's available locally, is called easy flo 45.

                One thing I found to make it easier to silver solder is to heat both parts till they discolor, etc, then let cool. Clean both up well, then re-heat for the silver soldering operation.

                It helps to have a gap for the solder to wick into, so when you machine the parts, make it about a 3 thou loose fit. Then put punch marks around the inner part, the nut in your case, such that the dimples you raise make the parts a tight fit again. Now you've got some room for the solder to flow into.

                I would wipe some flux on both mating surfaces before pressing the pieces together, to ensure that there is flux within the spaces. When you heat, the flux will already be preventing oxidation in the gap and the soldering should go well. One more thing- it helps to chamfer the edge of the hole and the nut, so when they are pressed together you have a bit of a vee where you would apply silver solder. Think of it as the gap between the parts being a bit bell-mouthed- this is a 'wick starter'.

                And yes, you do need the right flux.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #9
                  You are going to a lot of trouble to avoid threading a hole. It's true a 1" boring bar won't fit, but you don't need a 1" bar for a hole that is only 1 - 1.5 inches deep. Look at this:

                  http://www.wttool.com/product-exec/product_id/37871

                  3/8" diameter and three inches long: it's plenty long enough and narrow enough for the job. And it only costs a few dollars. Grind one end of the tool bit to bore the hole and the other for the threading. Start off by drilling to 5/8" or 11/16" or 3/4" or so and just bore the rest. Then thread. A lot easier than all that soldering and the thread will be a lot more concentric.
                  Paul A.
                  SE Texas

                  Make it fit.
                  You can't win and there IS a penalty for trying!

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                  • #10
                    True silver-solder is very fluid once molten, and will wick into .002" gaps very nicely; it has little strength when filling large gaps. Cleanliness is very important; I find a dilute hydrochloric acid pickle very useful in getting solder to wet steel surfaces. When I silver-soldered the 110 copper-steel joints in my steam launch boiler, I found that, after a thorough brushing, heating the steel nipples to 300F or so (guesstimated) and then cleaning the joint surfaces w/ an acid brush and hydrochloric acid (stay clear of the fumes) prior to fluxing made getting leak free joints pretty straightforward; I had one joint leak afterward and it was readily repaired.

                    I'd use a brazing flux containing fluorides even though they're toxic - they seem to work best. If you use cadmium-bearing solders, be careful not to overheat the solder as the resulting fumes are quite toxic.

                    For small parts, particularly of brass or bronze, you'll find a propane torch easier to use, and less prone to locally overheating the parts.

                    - Bart
                    Bart Smaalders
                    http://smaalders.net/barts

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                    • #11
                      Originally posted by barts
                      For small parts, particularly of brass or bronze, you'll find a propane torch easier to use, and less prone to locally overheating the parts.
                      And now we're at the reason for my question. I was trying to braze a part a few days ago using MAPP gas. The rod was fluxed brass and of course it would not melt. I got out the O/A torch and made short work of it. My guess is (can you tell I'm no expert, here) that fluxed brass won't work with lo-heat gases. I've soldered miles of copper pipe (and never had a problem with Chinese toxic drywall ) but have never had luck using propane or MAPP with brass rod. Is that normal?

                      And apologies for hijacking the thread - it might be a good one to start fresh.

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                      • #12
                        Mapp and Oxygen are perfect for brazing brass or silver solder, harder to overheat the joint. use a borax flux. I do not think straight Mapp will work with anything but the lowest temp silver solders
                        --
                        Tom C
                        ... nice weather eh?

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                        • #13
                          Originally posted by dp
                          And apologies for hijacking the thread - it might be a good one to start fresh.
                          No apolgy necessary dp. All good info to me.

                          I just did a google on hydrchloric acid, wondering where I might get some, and I see it is known historically as muriatic acid. I already got some of that! Thankfully one bottle still has a label and I see it's 29% hydrochloric acid. Somewhere in that google mess I saw 18% was good for a pickle, 50% more water should do that, but for how long?

                          barts?

                          That and I need to get some kind of known silver solder and the flux that's designed to work with it.

                          SP

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                          • #14
                            Originally posted by Astronowanabe
                            Mapp and Oxygen are perfect for brazing brass or silver solder, harder to overheat the joint. use a borax flux. I do not think straight Mapp will work with anything but the lowest temp silver solders
                            There's the problem - my MAPP gas was burning the same air I was breathing. Hot, but not hot enough.

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                            • #15
                              Paul A., I know you're right in that a 1"x8 tpi thread shouldn't be a big deal, and I've got a 3/8" boring bar among numerous others, but internal 8 tpi without giant amounts of chatter out of me and my Logan is an enormous amount of trouble. My 1st backplate took weeks and about 4 times more metal than was necessary. The major thread on the subject was titled "Still No 8tpi" and it ran for 4-5 pages until the good members here on the board finally got me thru it.

                              I have since used those lessons to make another for a sweet little 8" 4-jaw I got from BadDog, but it wasn't exactly easy. Believe me, a 3/8" bar in a smaller hole trying to cut those big ol' 1/8 wide threads is not going to be pretty ....

                              SP

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