Adjustable Allen Key After All These Years

The Allen key turns 115 this year. It’s strange to believe that in all that time, no one has come up with an adjustable version, but apparently true. Luckily [Chronova Engineering] has taken up the challenge in his latest video.

The video is a fascinating glimpse at the toolmaker’s art–manual machining and careful human judgement. Humans being the fallable creatures we are, the design goes through a few iterations. After the first failure in metal, [Chronova] falls back on 3D printing to rapidly prototype the next six iterations. Given how much work goes into manually machining the designs, we can only imagine the time savings that represents.

The final version is has classic hexagonal rod split in two, so that a chisel-shaped rod can spread the two prongs out to engage the sides of the Allen bolt. Even with that settled, the prongs and wedge had to be redesigned several times to find exact shape and heat-treatment that would work. At this point the range is anything between 4 mm and 6 mm, which is admittedly narrow, but [Chronova Engineering] believes the mechanism has the potential to go wider.

The design is not being patented, but the drawings are available via the [Chronova Engineering] Patreon if you really need an adjustable Allen key and don’t feel like reverse-engineering the mechanism from video. It’s a much larger project than we’ve featured from this channel before– enormous, really, compared to steam engines that fit on pencil erasers or electric motors that squeeze through the eye of a needle.

Our thanks hall-of-fame tipster [Keith Olson] for letting us know about this one. If you want a slice of that fame for yourself, the tips line is always open.

40 thoughts on “Adjustable Allen Key After All These Years

    1. Yep I got a set of metric and sae long bits with a quarter inch drive for peanuts on Amazon and they fit into deep counter bores easily. Not to poop on the project its a interesting idea and the execution is nice… but I would rarely if ever use it just like my grandfather’s adjustable flat head driver (which looks darn new because its functionality useless in most situations)

      1. While it’s nice. I think he missed a trick here. Just thinking out loud but couldnt you use a drill/lathe chuck design but split it into 6 pieces and each of the pieces is just a corner piece at a 60 degree angle? Obviously a small one wouldn’t have the best grip in the edges as it gets bigger, but you’d get a much better range of device for sure as the angle is always the same no matter the size of the Allen key/wrench, it still has 6 corners that meet at 60 degrees.

          1. This site is so bad about that. It’s like they have ontouchstart set to open the comment dialog. Every dang time I try to scroll, it instead shoves the comments off the bottom of the screen due to opening the comment dialog.

        1. That was his first draft attempt, but the six fingers each lacked the required strength. He also tried a three finger version but it was still not stiff enough so the two finger design won in the end.

    2. Assuming you actually have a bit that will fit right neatly organised by size – between metric, imperial and worn out or low tolerance bolts this could well prove faster than hunting through the metric, only to find none of them are right, going over to the imperial and perhaps then finding none of them really fit right either. Or worse finding that empty spot in your tool organiser where somebody has taken and not returned, or it happens to be the bit you broke and haven’t replaced yet…

      1. Or, here’s an idea, maybe the US does the right thing and finally ditches imperial tooling and hopefully the whole system. As a Canadian, I’ve done it in my own home. Sold all imperial/bilingual tools and fasteners and replaced them with metric ones. It’s liberating. I’ve literally cut the space needed for screws in half. Using a single system also means the tools themselves become more useful, the greatest example being tape measures and rulers, that can now be used on both sides.

    3. This can literally also be said of adjustable wrenches. Much faster to grab the fixed size wrench you need than fumble with the thumb screw. The point of adjustable tools is not to be faster, it’s to have a single tool that can do many things, the primary concerns being space, weight, and money savings.

  1. I swear I remember my father having a tool that was a series of nested spring loaded hexagons that let you attack any allen bolt with just a wiggling press. Like those socket wrenches full of pins, it sorta kinda worked sometimes when the moon and stars aligned just right.

      1. The one we had also had a screwdriver type handle but if you needed extra torque, they had a neat design feature. As someone who has often resorted to using a crescent wrench for torque I really appreciated that they designed it so the butt end of the handle fit perfectly in ~1-1.5″ socket (I cant remember what size exactly).

    1. He does mention this while building his version.

      Also, this was made for another Maker on YouTube. Different makers were asked to make something for another maker.

      Inheritance Machining made a puzzle maze for I’m Not an Engineer, and he made a awesome looking mechanical counter for AlecSteele and so on.

    1. Agree.. they take up so little room now.. but might me a good idea for something like carrying it on my motorcycle tool kit when I only need like 4mm thru 6mm. But even then… not really. I did enjoy watching the process of him making it..

    1. I tend to think that a perceived lack of practicality led to the decision to release the design into the wild.

      Maybe crowdsourcing can find some sort of trick to make it workable.

  2. It’s too bad that this would only really be good for the larger sizes, which tend to fit the best, cam out the least, and are the easiest to tell apart on the allen key rack. The tiny ones are far more irritating.

  3. The amount of unadulterated autie criticism on here is wild for such a high quality project. Just because you haven’t realized the use of a tool does not make it useless. Maybe you are just a bit dim.

    As someone else in the comments points out, this, when fully fleshed out in terms of range and easy adjustability would absolutely have its place in many work benches, or even more so many field kits. No need to lug 2 whole sets for imperial and metric out to a job site. Just one tool.

    The space saving would be the only selling point some would need as well, for those with small workshops where you gotta go and dig out the right set and pack it away again vs just the one tool in your drawer.

    I’m sure he thought of this and threw it out for some reason, but it seems like it would be ideal to be able to get 4 or at least 3 separate contact regions. Make some sort of nesting central wedge that allow you to just jiggle it until it spreads to maximum contact. And then watch with sadness as the whole thing bends on the first mildly tight bolt. I dunno I’m not a tool maker.

  4. If it were able to achieve a really tight hold it might surpass the grip of correctly fitting hex key and not round out on a very tight bolt, this would obviously have to be quality tool to achieve this !

  5. Wonderful work and a joy to watch!! And I admire his perseverance at trying over and over until he has the “perfect” design…
    …But it is not much smaller or easier to use than an assorted set of normal hex keys. Which is probably why nobody tried this before.

  6. uh, ironically, you want “fallible” not “fallable”.

    As someone who sees a lot of errors in published works, I’m curious, why did you choose to not use a spell check?

  7. I think many commenters aren’t getting it… It’s an old joke. Asking someone for an adjustable Allen wrench or muffler bearings. It’s a clever answer to an ancient joke. Sheesh

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