However, I note that real life allen keys have rounded edges, and the exact fit is never going to happen anyway. However - you may well find that for all but the very smallest ones, that's good enough.

It really helped with the drill bits to have something that will work quickly and simply so I'm hoping someone will have a suggestion? Otherwise it'll probably be a case of resorting to callipers which seems cumbersome and time consuming.

I'm on a mission to tidy up our workshop, which has not been helped by an influx of tools that we recently acquired from a liquidation auction. One of the niggling problems is a large collection of random allen keys.

Personally I just keep all my standard right angle Allen keys in a drawer ( small flat store form style filing cabinet) and grab a likely selection to try.Unless you know the size of the socket, knowing the size of the tool isn't much help.

0.9 mm hex wrench1 2

Vernier caliper. It will allow you to distinguish between metric and imperial size hex keys and you can use it to measure lots of other things like drill sizes etc.

100 bonus marks for Dave M. Who can tell what size Allen key is needed from staring down a hole and why bother becoming an expert anyway?

In workshops flat trays or old plastic drill boxes are handy but the main thing is to have sets without duplicates which can then be removed and kept in a box under the sink (proverbial sink). Sorting them into sizes using sockets is an old mechanic wheeze and something done once in a blue moon to remove those doubles.

0.9 mm hex wrenchnearby

I ended up with one of those "penknife-with-multiblade" sets from Stanley and gave all my rusty ones away. For £4 you can get a set of 10 on a keyring like we had in the dark ages before plastic. These things are so cheap today it is hardly worth the labour cost of messing around.

0.9 mm hex wrenchmetric

I just bought a second electronic vernier that does depth as well as internal /external in metric/ imperial decimal/ expressed as fractions. In stainless steel for £20 at an autojumble

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Thanks for all the replies. I've already got a set of digital callipers, Dave M's model sounds better, but I've found it a bit of a fiddle especially when there's a good quantity of keys to sift through. Poking through holes like we do with the drill gauge seems a lot quicker.

A while ago I discovered Drill Gauges which have made organising our drill bits much easier. I figure that something similar must exist for allen keys. The drill gauge won't work because the holes are round, so the diameter won't match, but I do wonder if there's something similar which I could repurpose.

My problem with this approach is that Murphy's Law comes into play, and if you grab a handful of, say, five keys three out of the five will be the same size and none will be the size you need. At least if they're organised by size I can grab a spread of sizes.

I do have a set that are in a plastic roll like spanners. Once you get a size , a bit of tape with the size on it might help keep order.

Sir Oliver's Horse says that if an allen key fit's exactly to the edges of a drill hole, then it is 0.87 of the size. So easy to make a quick reference chart.

I'll try it out later on. Next challenge will be stopping any of the sockets from getting pinched to do jobs elsewhere...

That sounds like a genius idea, especially since most of the allen keys are small enough that it's going to be a relatively cheap set...