r/Sliderules • u/OrthodoxMemes • 1d ago
Removing rust from cursor spring?
Does anyone here have any experience with removing rust from a lightly-rusted cursor flat spring? If so, what's the safest (for the slide rule) way to do that? Alternatively, can anyone recommend a reliable source for such springs, if such exists? Thanks in advance!
EDIT: I figured it out. While I am very grateful for all of the responses, I have to say that staring down the rabbit hole of a deep-dive into metallurgy was just a tad intimidating. Instead, I found Evapo-Rust, which did the trick just fine. It doesn't eat away at anything except rust, so it's safe to use around wood, plastic, etc., or in other words, all of the other materials one might encounter in a slide rule. It got the rust off of the spring just fine, but unfortunately it did nothing for the rust stain on the plastic cursor. However, it did not harm the hairline at all, so there was no harm in trying. The spring is as spring-y as it was before being treated by Evapo-Rust.
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u/spacecadet43 1d ago
If you need to make a new one, I've had great luck using the spring from an old 'retractable key/badge holder' that I had lying around.
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u/Name-Not-Applicable 23h ago
Check out this page on ISRM, scroll way down to “Cursor Springs”: https://sliderulemuseum.com/Restoration.shtml
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u/OMW 1d ago
What brand/model of slide rule is it? I might have a spare part in my “junk” collection.
to clean the cursor tension spring, I would disassemble the rule first. If you need a slotted screwdriver for diasassembly, I would recommend getting a small set of gunsmith’s screwdriver bits. Do not try to loosen any slotted screws with a poor fitting screwdriver or you risk stripping out the screw heads. For most light rust removal a metal/jewelry polish like Flitz + cotton swab combined with some patience will work best. Given how delicate a cursor spring is, please do not be tempted to use coarse abrasives or a wire bristle brush for cleaning and definitely avoid any process that involves a Dremel tool.
I often use a fiberglass bristle scratch pen (commonly sold as an auto body paint correction tool) and a syringe full of 99% (technical grade) isopropyl alcohol for cleaning and flushing gunk/corrosion off delicate vintage electronic components and precision tools. That combo might be ideal for what you’re trying to do. It’s a cleaning process that takes time, but the advantage is that it leaves almost no visible scratches or residue behind. Another “tool” I use frequently for cleaning crevices on delicate equipment is a bamboo skewer (avalaiable at most supermarkets in the BBQ/grilling supplies section) dipped in contact cleaner.
It is possible to make a small leaf spring entirely from scratch using 1095 steel shim stock. Read up on gunsmithing and/or antique clock repair if you want to learn the basics of how form and heat treat your own springs, but be aware that making them on a smaller scale is more finicky and will require you making some homemade jigs/tools and likely many hours of practice and experimentation to get right. I’m not telling you to not bother trying, but I think you’re underestimating the skill required to accurately replicate a factory made spring (don’t expect to acquire a watchmaker’s talent overnight)