Sweeney Trev

With apologies to Stephen Sondheim.

Yesterday’s mailbag included a wonderful package – the repaired probe for my resistance soldering rig.

I’ve written about the probe problem elsewhere, so I won’t repeat the story here in great detail. But for the TL:DR crowd, I’ve been building fleets of model railway equipment since late last fall, all in brass – which means I’ve been using the resistance soldering unit a lot. This work consumes the probe’s tip, which is held in place by a grub screw. In May, the screw corroded, locking it in place. I could not remove the screw, so I could not replace the tip – which meant no more soldering until I sorted the problem.

Having failed to fix it myself, I sent the probe off to my friend Chris Abbott, who was able to remove the grub screw. He then cleaned up the threads in the probe, and replaced the now destroyed grub screw with a socket-head cap screw: You can see the new fastener, just behind and above the tip, in the lead photo for this post. The cap screw accepts an Allen Key, although I can also finger tighten it.

The big advantage over the grub screw is that if the cap screw seizes, I can get a pair of Vise Grips on it – not that I plan to let it seize. As noted previously, going forward I’ll remove the fastener and probe tip after each work session, then shoot some contact cleaner on both the fastener and through the hole into which it screws. It’s a few extra steps but it’ll save me grief in the long run.

Thanks for the great work and speedy turnaround, Chris: I’m looking forward to returning to my various brass-building projects!

Published by Trevor

Lifelong model railway enthusiast and retired amateur shepherd who trained a border collie to work sheep. Professional writer and editor, with some podcasting and Internet TV presenting work thrown in for good measure.

5 thoughts on “Sweeney Trev

  1. Long, long ago, in another world, I periodically had to replace the muffler on my VW beetle. After the first fiasco, I applied graphite paste to the mating surfaces. It worked in that application – steel on steel with significant temperature fluctuations. I recently brought a tube in a local auto parts store. Might work for you?

    Liked by 1 person

    1. Interesting thought. This application also involves electricity and graphite is conductive so it may simply burn out. I think I’ll be fine if I just clean the screw after each soldering session to make sure there’s no flux on it.


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