Soldering/Welding Techniques

Discussion in 'General Electronics Chat' started by cmartinez, Jul 15, 2019.

  1. SamR

    Well-Known Member

    Mar 19, 2019
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    Bench grind
    Bench grinder w/ wire wheel and leather gloves and face shield. Extra small parts use vise grips. Soft metal (including Silver solder) small air blast booth with rubber gauntlets using walnut hulls or glass beads. Need room for booth and air source plus blast materials and clean up when done. Blast materials can be reused.
     
  2. cmartinez

    Thread Starter AAC Fanatic!

    Jan 17, 2007
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    A little too late for that now, I'm afraid. And sandblast is out of the question, I don't have the equipment and I don't want to risk abrasives getting into the joints.

    I also read that passivation can be obtained using citric acid, is this true? I know where to find nitric acid, but I'm very much afraid of it, and I'd like to avoid using it if I can.
     
  3. SamR

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    Mar 19, 2019
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    There is another way for small parts. Rock tumbler. Tumbling medium can be had for all kinds of applications.

    https://www.harborfreight.com/dual-drum-rotary-rock-tumbler-67632.html?cid=paid_bing|*PLA+-+Top+SKUs+-+All+(High+Intent)|Rock+Tumblers|67632&utm_source=bing&utm_medium=cpc&mkwid=LzfVBTj0|pcrid|{creative}|pkw||pmt|be|pdv|c|slid||product|67632|pgrid||ptaid||&pgrid=1170980177767519&ptaid=pla-4576785874941907&pcid=368003273&msclkid=761f23b4e4fa1644e6b27e9a66f6cb93

    You keep saying passivation... I am talking about cleaning and with the correct stainless alloy passivation is not needed. We primarily used 304L for chemical piping and never treated it. For marine use, 316. Use the alloy you need for its intended environment and passivation not needed.
     
    Last edited: Jul 16, 2019
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  4. KeepItSimpleStupid

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    Mar 4, 2014
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    Boil it anyway. It just might take longer.

    Think about regular flux. It was much easier to use the flux remover shortly after the board was soldered.
     
  5. cmartinez

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    Interesting ... maybe I could preheat it a little with the torch from afar before dipping it in the boiling solution you're suggesting. Perhaps that way it will take even less time.
     
  6. jpanhalt

    Expert

    Jan 18, 2008
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    Hot dipping may help.

    I searched on cleaning after brazing/hard soldering and came up with "Fuze-Clean FS." It's a mixture of acidic salts that is presumably active in just hot water: https://www.fusion-inc.com/cleaning/

    Here is a link with links to its MSDS/SDS and instructions: https://www.sra-solder.com/fuze-clean-fs-powder

    I have no experience with it, as I tend to home brew something or use a mild abrasive (walnut shells or glass) -- not sand.
     
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  7. cmartinez

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    So, I did what KISS suggested, and boiled the part in 300 ml of purified water to which I added three teaspoons of baking baking soda for 30 minutes. I made sure to keep the water level above the piece at all times by adding a little more water when necessary.

    When I took the piece out, it was a disappointment because it looked exactly the same as before. But then I noticed that my fingers were getting stained with a black substance coming out of the part and, lo and behold! it started to come loose when I rubbed it with a toothbrush.

    So I again took my Dremel tool attached with the wire brush wheel and gingerly set to try to remove the black scales once again. It worked like a charm. :)

    The part still shows dark discoloring due to the heat that was applied to it, but it no longer looks as bad as it did. And what's more, its hinge is now moving far more easily as it did before. I'm guessing that's because the baking soda got into the gap between the axle and the hole and cleaned whatever scaling had formed within.

    Image00001.jpg
     
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  8. Janis59

    Active Member

    Aug 21, 2017
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    Seems 1200C ir bit high for stainless what becomes soft already at 800. Even it melts much higher, the metal will be deformed and ugly. Stainless may be well soldered by ordinary Pb-Sn solder at conc H3PO4 flux or superconc ZnCl flux, or acetilsalicil-acid as flux. Or alternatively, it may be soldered with torch, using the copper, Cu-Phosphorus, missing and bronze solder metals, with flux of acidi borici, or borax, or better mixture of those both, the borax in majority. As well, the old soviet epoch russian coins may be used very well, as copper-nickel alloy, as even white type, nickel alloy.
     
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  9. cmartinez

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    Thanks for the suggestion, Janis. Fortunately, the pieces did not deform. But I'd definitely like to learn a method for soldering SS that uses less heat, like the one generated by a butane torch, instead of the MAPP/Oxy mix that I had to use
     
  10. shortbus

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    Sep 30, 2009
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    This is the best soft solder flux I ever used with stainless, https://www.castolin.com/product/157 but it is corrosive and needs to be cleaned off after soldering.

    The StayBrite8 and it's flux, that i referenced earlier, work well as a team and are as strong or stronger than most silver solders and use less heat.
     
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  11. KeepItSimpleStupid

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    https://americanbeautytools.com/Resistance-Soldering
     
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  12. cmartinez

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    Now that's very, very interesting. What I'm working on right now is just a prototype, so the amount of time invested in this artisan-like type of work is justified. But I'm planning on manufacturing these things, and the system you've just shown me fits the bill perfectly.

    Many thanks!
     
  13. MrAl

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    Jun 17, 2014
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    Hi,

    Wow what a beautiful metaphor "harder than a witches heart". :)
    I've also heard "colder than a witches t.." ha ha.

    I like yours better though.
     
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  14. MrAl

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    Jun 17, 2014
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    Hello,

    When you solder you normally heat the work and the work melts the solder, but to start the melting process you might have to melt a little at the end with the heat source so that the solder makes good contact with the work and thus transfers enough heat to keep melting it.

    I used silver solder years ago when i had to fill in for the guy that soldered the SS bands around certain U core transforme/inductor cores. We used a giant soldering iron maybe 500 watts with a big copper tip. You had to heat the work really well.
     
  15. KeepItSimpleStupid

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    This guy was manufacturing model train stuff from brass that was cut by etching. Not sure if laser cutting existed in the 80's. He was using a torch and "dripping" the solder. So, I told him about resistance soldering and he used it.

    We had one at work that I used to solder pins. I ended up using stainless brazing electrodes for the contacts on the tweezerss.
    So, you have a high current, low voltage variac, a foot pedal and a pair of tweezers. You just have to make contact before activating the foot pedal. Then an occasional sanding of the electrode.

    Instead of pointed electrodes, I flattened one side to give me a better contact area.

    If you don;t need that strong of a joint, can you just press the pin in place?

    Drill. Then use an undersize reamer and press in place. Depends on your pin. You have over/undersized reamers for slip and press fit.
    To solder, you need a gap.
     
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  16. cmartinez

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    Press fitting has been on the table from the very beginning, and I intend to eventually test it thoroughly. But the first parts were laser cut (including the orifices for the pins) and the tolerances are not good enough for reliably press fitting the pins. And I don't have the capability of accurately locating and drilling the holes in-house on a pre-cut part at this point. But that will change when production starts.

    Question do you know a good way of quickly cutting the SS pins (5/32" and 1/8" in diameter) to a ±0.005" length tolerance (maximum length about 1-1/4", minimum about 1/4"), and (the most important part) having slightly rounded edges? Is there special machinery already out there for this task?
     
  17. Yaakov

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    Jan 27, 2019
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    Just an idea: depending on the force the part will experience, you can use what my Scottish machinist colleague called the "puttin on tool" for a press fit. Just make the holes consistently pass fit, and knurl the section where they are to be press fit. The knurler was the "puttin on tool". When he first suggested it to correct an outsized hole, I though he was joking, but it worked like a champ.
     
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  18. jpanhalt

    Expert

    Jan 18, 2008
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    Abrasive cut-off (preferably with cooling) and grinding to final length. BTW, I use a cheap aquarium pump for my cooling when heating is an issue.

    Edit: I use a miniature abrasive cut-off saw for the small tubing used in modeling.
     
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  19. shortbus

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    Sep 30, 2009
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    https://libertymachinery.com/process-descriptions/screw-machine-process-description/

    you probably already know to try and use diameters of your tube s and pins that are commonly available stock sizes, to keep from having to machine every surface, the surfaces that aren't important to the working of the device.
     
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  20. cmartinez

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    Thanks, Shortbus. I knew I could count on you for this one :) ... that thing looks rather expensive, btw.

    Yes, of course I try to design everything I make based on available commercial material stock sizes. I could easily build a machine that automatically cuts stock SS rods to length with a high degree of accuracy. It's the slight rounding (or at least chamfering) of both edges that has me a little worried though.
     
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