Sunday, November 10, 2013

A discussion developed on the Old Tools List concerning a problem one of the guys had.


The items to be soldered are copper sheet and brass rod.
How does one solder without melting the adjacent seams?
Is a heat sink in order, if so, is there one that doesn't require  clamping?
Is using conventional supplies such as lead free solder and flux,
handiman propane torch typically used to sweat copper  acceptable?
If anyone can help maintain my status, I know its you folks.
Bowing and scraping in advance...
Bob in Ohio

James Thompson

A bare soldering iron doesn't transfer heat well. It needs liquid solder on it, and the liquid solder is what transfers the heat. The solder will flow easily onto a closed joint if the joint is clean and fluxed. Open joints require  you to add a little solder, wait for the heat to dissipate, then apply more solder, repeat, etc. Dress off any lumps later with a file or other abrasive.

And if you are making a continuous joint, do not lift the iron up off the joint when you are done with that joint. Move the iron back a short distance and drag it sideways out of the puddle. Sounds strange, but believe me, it is the right way to terminate a solder joint.

Troy Livingston
You might try Tix solder, almost the same strength as soft solder but
with a much lower melting temperature.

Taking a bit from both James Thompsons and Troy Livingston posts I have been in a similar situation in manufacturing and hobby work.

I used to work for Borg Warner at their Coldwater, Michigan plant. We made radiators and heat exchangers. Most of the work was short run and or prototype so the plant was equipped to build every part of a radiator, tubes, fins, header, frame, everything.

The tubes were soldered with higher temperature 40/60 solder. In other words, more lead in the mix. To keep from causing leaks in the tubes the headers were soldered to the tubes with 50/50 solder with a slightly higher tin content, and a lower melting point.  If there were repairs needed they were done with 60/40 a mix with even higher tin content.

Finding lead solder is difficult anymore. To prevent lead contamination, plumbing solder is now made from tin and silver 95/5. It has most of the desirable properties of the old 60/40 without lead.

The website below lists different non-lead alloys and their melting points.

Home experience has involved repairing a little galvanized bird house that SWMBO had purchased at a garden supply store. As always she had a plan for how the arrangement was to work and when the bottom broke free from one of them the plan was disrupted. With parts in hand she came out to the shop and asked if there was anything I could do. The bird house was 3” square and strictly ornamental. Using a large dual range electric soldering gun on low, I was able to heat the joints just enough to fuse the existing solder back together without heating adjacent joints to failure.  A quick overlay of 60/40 solder from my stash and SWMBO was ready to complete her plan.

37 years of marriage and now you know why. Happy wife, happy life. 

PS. When I go through smaller towns I always shop at the local hardware store. I occasionally find caches of lead solder because everyone is using the plastic and hose clamp crap now. My shop is a haven for out of date supplies and materials.

Dave N.
aka Old Sneelock

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