The interior of a failed boiler.

Fail Of The Week: Learning How Not To Silver Solder

Sure, there are subtleties, but by and large it’s pretty easy to pick up soldering skills with a little practice. But wait! Not all soldering is created equal, and as [Quinn Dunki] learned, silver soldering is far harder to get right.

Granted, the job [Quinn] is working on is much more demanding than tacking some components to a PCB. She has been building a model steam engine, a task fit to put anyone’s machining skills to the test. And a steam engine needs a boiler, which is where the silver soldering comes in. As she explains in the video below, silver soldering, or “hard” soldering, uses solder that melts at a much higher temperature than “soft” solders like we’re used to in electronics. That’s a big advantage in the heat and pressure of a boiler, but it does pose some problems, many of which [Quinn] managed to discover as she tried to assemble her copper beast.

It turns out that heating a big hunk of copper evenly without burning off the flux actually isn’t that easy, though you can’t say she didn’t give it the old college try. In the process, she managed to share a number of tidbits that were really interesting, like the fact that drawing acetylene from a tank too fast can be dangerous, or that model steam boilers have to be certified by qualified inspectors. In the end, her boiler couldn’t be salvaged, and was put to the saw to determine the problem, which seems to be her initial choice of heating with oxyacetylene; after that initial failure, there was little she could do to save the boiler.

As [Quinn] says, “Failure is only failure if you don’t learn from it.” And so it may be a bit unfair to hang “Fail of the Week” on this one, but still — she has to go back to the beginning on the boiler. And we already know that model steam engines aren’t easy.

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Oil Feed Retrofit For A CNC Mill Starting To Come Together


Here is the first real fruit of [Joel’s] labor on his oiling system for a CNC mill. Regular readers will remember hearing about his quest to go from a manual mill to a CNC version. As part of the overhaul he decided to add a system that can dispense oil to the different wear parts on the machine. We first looked in on the project when he showed off the pipe bender he built for the task. Now that he has that at his disposal he was able to route tubing to many of the parts.

The system starts with a central brass manifold which is pictured in the foreground. Each pipe was bent and cut to reach its destination with a minimum of wasted space. After a test fit showed good results he brazed the pieces together using silver solder. Each of the ball nuts have been drilled out so that oil will be injected onto the threads of the ball rod. Three input ports on the manifold will eventually let [Joel] connect the oil injection system via flexible tubing.