Gluing copper to mild steel ? - Page 2
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  1. #21
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    Keep in mind that epoxy requires a relatively largish thickness to bond. Epoxy does not do well in very thin spaces. Assuming you are bonding to flat machined surfaces and can maintain .001 to .003 maximum between surfaces, normal Loctite in any variety will work much better than epoxy. I often do this as a means of temporary holding for machining of awkward parts. The beauty of Loctite is that it is strong and removable with heat.

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  3. #22
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    Quote Originally Posted by Forrest Addy View Post
    Clean and tin both surfaces. Clamp them gently, heat til the excess solder squishes out.

    Stay flat? That wasn't part of the original problem. If both steel and copper are thin, there will be some dishing because of different thermal expansion rates. But if the steel is thick and the copper thin there will be little distortion. If flat is important I suggest you provide stock allowance for post-solder machining.

    Soft solder takes place at 400 to 550 F depending on solder alloy. 2500 to 4000 PSI bond strength, again depending on solder alloy. I suggest a 95+% tin, 3% silver 0.8% copper alloy as being stronger, having better wetting, and lowest melting temperature of all but 37% tin 63%lead solder. Use the right flux.
    Thank you ! That's why I always look for your posts. The steel is 18mm thick. I did a small test and worked 100%. Tinning the copper was easy. Tinning the steel seems to be a tad more involved. But it's worth the trouble given the cost of copper nowadays.

  4. #23
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    Quote Originally Posted by Spruewell View Post
    I'm assuming you are trying to lap the copper disks and want to use a steel plate to back them. In that case, you could also use a spray adhesive. 3M has an extensive line of adhesives that may work. Epoxies will hold the parts together, however if you plan on removing the copper from the steel backing it will probably not survive. Solder will allow the copper to be removed, but the solder itself may prove difficult to get off the copper.
    Interesting that you mentioned but I have ( had..) a constant need for a good spray adhesive and I NEVER found even a half decent one. If you could recommend a specific one, I'd appreciate.

  5. #24
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    I worked at an electrical engineering place a while back. They tinned copper contacts to steel arms for the large circuit breakers they manufactured. What they used was a thin sheets of solder a bit like 0.010" shim steel. The sheets were cut into strips and the strips were placed between the contacts and the arms, lightly clamped together and the whole lot was gently heated up until the solder ran. It worked a treat.

    This was a few years back now, I wouldn't know where to get the sheet solder from.

    I used the same solder to attach a piece of carbide to a steel shank when I was messing around making way scrapers.

    Regards Tyrone.

  6. #25
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    Clean the steel by vigorously scrubbing with Comet bathroom cleanser and a fresh ScotchBrite pad.

    Note: Do NOT clean afterwards with acetone as it carries small amounts of non-volatile impurities.that interfere with tinning. People who do are sadly misled. Search Dan Gelbart" on YouTube for the true skinny on paint and solder prep. He has 18 or so videos that should be required viewing for anyone building stuff that involves metalworking.

    Coat the cleaned steel with flux immediately and tin. Even then you may have to scrub the tinning into the steel with a small wood handle wire brush. Use a clean brush never used for another purpose.

    Come to think of it, the steel will hold its heat for some time. If you quick like a bunny mate up the pre-tinned copper, back it with a flat preheated block of wood then clamp it, there should be enough residual heat from the steel to solder to the copper. If not you can always apply a little more torch heat to the back side of the steel. 400 F won't do more than lightly scorch the wood. Don't death-grip the clamp. Snug is fine. Squeeze out too much solder weakens the bond.

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  8. #26
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    Dubblesided tape with a little heat
    You have all kind of varities in all kind of thicknesses

    Peter

  9. #27
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    Scotch brite the surfaces to roughen them up then use some loctite 680

  10. #28
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    Quote Originally Posted by SeaMoss View Post
    Explosion welding !!!
    That's the ticket!!!



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