How To Clean Bolts And Nuts

This is a grade 8 bolt, four inches long, one inch thick, made in the USA by Nucor Fastener. It has a tensile strength of 150,000 PSI -- well over twice the strength of a "common" grade 2 bolt with no markings on the head. It also has a history; those chisel marks on the head tell me a story of a long day, a torch, a broken cheater bar, a cold chisel, a heavy hammer, a lot of cussing, and, finally, a talented mechanic who not only knew how to break it loose, but had the self-control not to throw the miserable fuckin' thing as far as he could into the weeds when he finally got it out. I never knew that guy, because I bought it from his estate sale, along with fifteen more gallons of similar hardware. I don't know him, but I've known plenty like him, including my own father.

There's some corrosion markings on the bolt head and some rough spots on the threads, that I couldn't see under the original coating of rust. Until I find and clean a matching nut, I won't know for sure if the bolt still threads. A purist might prefer a new one, but a man who needs a good hard grade 8 bolt this size might decide to make it work. Especially considering that a new replacement of this grade/quality will cost you fifteen bucks if you're buying in retail quantities. At the tractor dealership, you would put in a new bolt and bill the client for top-notch perfectionist work. In your own shop, well, it depends.

Anyway, this is an old thread but the problem of bulk hardware cleaning persists. What really got me thinking about it again was the related problem of rusty tool restoration. I didn't work in the shop much during the pandemic, because the biggest risk of forced exposure to the virus where I am is/was a chance encounter with the cops in a traffic stop. None of those guys were wearing masks or respecting social distancing. So, until we got vaccinated, we weren't doing optional/frivolous driving errands, and the shop I play in is ten minutes away. Didn't matter so much, because I wasn't doing garage sales either, so I didn't have the constant influx of "new" goodies to play with and clean up. But now I do again.

I never tried an electrolysis experiment like we discussed higher in the thread. No matter how you set it up, you're generating potentially explosive gasses (oxygen and hydrogen) at the electrodes. It's easy to ventilate the risk down to virtually nothing, but in/near a borrowed shop it's not my place to be creating even tiny risks that are avoidable. So that line of experimentation remains for when I get my own shop space.

By chance I came across some videos of vibratory tumblers being used to clean rusty hardware. This was #6 on my list of approaches in the original post last year:

Dan Boone wrote:
6) Bulk vibratory abrasion methods. Similar to above but using a commercial vibratory cleaner vessel that just shakes, without tumbling. Always with a purchased abrasive medium, sometimes with added liquid. Noisy, usually requires an expensive purpose-built power tool, said to deliver pretty good results.

There's an almost-standard vibratory tumblr out there that comes in two sizes (small and bigger) from a variety of sources; it looks to me like there's one fairly expensive made-in-USA product (from Eastwood) and a whole bunch of copycat versions made in China and sold at places like Harbor Freight. All the copycats may be from the same factory with different brand names on them, as is common with Chinese-origin tools. The quality is said to be lesser.

What I learned from my recent spate of video-watching is that using these tumblers to clean rusty parts requires some technique. YouTube is full of unboxing-type videos where somebody gets the new toy, turns it on, dumps in the dry walnut-shell media (actually for polishing) that comes free with the unit, throws in some rusty bolts, runs it for a couple hours, pulls out the still-disappointingly-rusty bolts, and says some version of "well, they're better, won't need as much time on the wire wheel, I was hoping for more".

Then, too, a lot of those guys are restoring classic cars. They don't just want "enough rust removed so that the threads work again" -- they want mirror-polished bolts, every speck of rust and paint and original finish removed, so they can send their hardware out to be electroplated. Vibratory tumbling can get you a long distance closer to that, but my research suggests it can't get you all the way there. You still need a wire wheel or sandblasting step, and if you're gonna do that anyway, what did the tumbler really gain you?

Me, I just want all the crusty rust gone. I don't do projects that depend on hardware with perfect finishes.

Despite all the disappointed-newbie videos, a few -- very few! -- shop guys have videos that go further, experimenting with different tumbling media and especially with adding liquid (usually water) and soap (dish detergent or Simple Green most commonly). That makes the project a lot messier! But dust-free, so probably a lot safer.

The consensus seems to be that "the green media" -- basically, hard plastic triangles impregnated with mystery abrasives -- is the best stuff for rusty bolts/tools, but it has to be run wet to be effective. Downsides: the stuff is hideously expensive ($8-$10 per pound, and at the five-to-one recommended ratio of media to dirty hardware, you need 12-15 pounds to do a full load in the bigger-size 18lb-capacity tumbler) and worse yet, it's relatively soft, so it wears out fairly quickly. (How many batches? Nobody will quite say, but not all that many.) This would not work for me; beyond the expense, I am put off by the wastefulness of it. I need a thrifty media or none of this makes sense for me.

The second-best suggestion: "heavy media" such as ceramic triangles, cubes, and spheres, and/or tiny stainless steel pins (or old screws!) or good old-fashioned washed river gravel (some say, sand). Always run wet, always run with soap. Of course the stainless steel pins and fancy ceramic shapes are at least as expensive, when bought by the pound as tumbling media, as the plastic pyramids.

Because the heavy media is heavy, you can't really put enough of it in an 18lb-capacity tumblr to physically fill it as much as is needful. So there are different strategies for adding "bulking" media that is not so hard, but hard enough to be useful, and much lighter per volume. Small hardwood shapes, a variety of plastic pellets, the glass beads used in sandblasting cabinets, even oddball stuff like bone chunks or the little cubes of tempered glass that you get when you shatter a tempered-glass panel.

The deeper I got into the research, the more I kept hearing that, for the specific project of rusty bolts and tools, diversity in the tumbling media was the key, along with the soapy water. Lots of different materials in all different sizes and shapes, the more the merrier. As the softer items grind down into dust/mud, wash them out with lots of clean water (a bucket and screen is suggested) and replace them with larger items, so you always have a spectrum of size and varying textures.

And as for me? I am garage-sale-man! I can buy an endless amount of ugly ceramic tchotchkes for less than a dollar a pound, and do the world a favor by pounding them into "a diversity of sizes and shapes". I can "make" tempered-glass cubes or small hardwood shapes. This was beginning to sound more promising. (I could also get endless small collections of plastic beads of various kinds for nearly no money, but I'm really not interested in using plastic media; manufacturing a microplastics waste stream is not my idea of a socially-useful upcycling.)

So, after all this research, I got it in my head that I really wouldn't mind trying out one of these vibratory tumblers. And then serendipity! A side hustle paid off unexpectedly and I wound up with a couple hundred extra bucks in my mad-money account. Was gonna go to Harbor Freight but my amazing online-shopper spouse found a Chinese-branded version (almost certainly identical) on Amazon for thirty bucks less. Took a week to get delivered, but it arrived yesterday:

So far, I don't have any "light" media. And -- potential snag -- the instructions with my unit warn that using heavy media can "prematurely" wear out the plastic bowl. Fairly warned, I am. But (a) bowl replacements are readily available; and (b) I am pretty sure I can fabricate a better bowl out of a steel pot if the wear issues prove too severe.

For media, I did order two pounds of the expensive small mix of ceramic shapes, just to get me started. Plus I had a four-pound jar of nicely washed and pre-sorted tiny river stones from, perhaps, a big-box store garden center.

As for ceramic tchotchkes, they come in varying degrees of hardness; harder (porcelain) is better, whereas the thicker stuff is often a softer stoneware with a good glaze. I'm no expert, but I spent seventy-five cents last weekend at various garage sales picking out unloved and unlovable porcelain-looking ceramic items. The chipped mug was the real heavy-porcelain deal; far harder than the buddha incense holder (?) or the swan candlestick, and rather difficult to smash up.

All told, the media I threw in weighed about eight pounds, of my 18-lb weight budget. Throw in a pint of water, I'm at 9 pounds. Five pounds of rusty junk leaves room for up to four pounds of lighter media once I source some. Click the pic if you want to see the rusty crusts in high-res horrifying glory:

So, as my mother's bread recipe begins, "into the bowl, dump..." It quickly became clear that the concrete finishing tool didn't really fit; it was too large to become submerged in the limited volume of media. So I took it right back out. Added the pint of water and a splash of Simple Green. Started up the unit.

This all happened today. I ran the tumbler for two hours. Maybe one day I'll leave it running unattended; it is noisy. But as for now, I don't trust it not to vibrate off its table onto the floor, or not to disassemble itself from all the vibration. So I settled for a two hour test. It's my expectation that really challenging items may need to go for 8-12 hours, but bolt threads might suffer and get peened over from a run so long. I needed to look inside after two hours, for science; and I needed to go home anyway. Time to look:

And you know what? My excessively rusty hardware is manifestly not done. But the extent of rust removal, especially on the threaded items, is AMAZING! I am ridiculously pleased. I really can't wait to see what longer runs do for some of those rustiest pieces.

I was also pleased that two hours was enough to take all the sharp edges off my porcelain shards, so it was safe to rummage through the media with my hands to retrieve my stuff. I was not sure how long that would take.

There are several rinky-dink "features" to this tumbler. It has a drain hose that has nothing at the inside-the-bowl end of the fitting (like a screen?) to keep small media from vibrating down into the drain hose and lodging against the clamp. The main handwheels (modern plastic wing-nut equivalents) that screw everything together are prone to unscrewing themselves under vibration, and need more robust lockwashers (which I have). The gaskets between the bowl and the lid are not well-attached (not attached at all, actually) to either the bowl or the lid, so they keep flopping around and need to be secured with adhesive. Minor annoyances, but the mark of a tool either not-well-designed or that's been visited by the unit-cost-reducing suck-fairy.

That said, I like my new toy/indulgence. I think that if I baby it with great care, I can use it to easily clean big batches of hardware. I will, of course, report back as experiences accumulate.