Swiss Army style keyring V2 with thumbnail cutouts

by MarkBenson, published

Swiss Army style keyring V2 with thumbnail cutouts by MarkBenson Jun 4, 2013


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I love the Swiss Army Keyring by outcastrc, but using it is a little cumbersome. It needed those little cut outs in the side that allow you to get a thumbnail in to grip the key to make opening it that much easier.

So that's what this is. The Swiss Army style keyring with cut outs.

I have also moved the key ring clip as that was getting in the way of one of the keys.

This version is intended to be used with M3 nuts and bolts.

I've recreated the whole thing in openScad and the newest version is (mostly) parametric.

Update: I had messed up the dimensions after using the minkowski sum function to add the curved edges on this model. I have reworked the scad file to take that into account and the dimensions are now back to the same as the original. Also the new scad file is much more parametric. I haven't tested how tollerant it is when changing dimensions, you may have to alter a few offsets here and there. If you do change it, let me know how you get on.

I should also say that the one scad file now generates both sides. Just change the value of variable 'renderNutHoles' to either 1 or 0.

You will also need to include functions.scad file in the same directory as the main scad file to render the cutouts for the nuts.


Print both sides, fit M3 nuts or M3 lock nuts to the side with the hex recess. Fit three M3 screws to the other side, adding M3 washers between the sides and keys. Nip the screws up and if needed cut the screws down to length (measure, remove, cut and refit).

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I love the design and I use it daily. But a while I got in some troubles with the customs at the airport. They mistook it for a pocket knife and my they had to inspect my hand luggage which took an extra 30 minutes...

Aug 23, 2016 - Modified Aug 23, 2016

I've printed three versions of this, and they mostly work, except that loop which attached to the key ring will break after a certain amount of time. I have yet to own one of these for a full year. I made the most recent with PLA @ 90% infill, so its pretty solid. It's a great thing, but might take some fiddling to find a good solid material for it to work with.

I've just swapped my first printed one after 2 years. The loop was worn but not broken. It was printed in ABS @ 0.2mm layer height and 20% infill. I'd expect the loop to be printed solid regardless of the infill due to its size.

I now have one printed in CopperFill PLA @ 0.1mm @ 20% infill. It will be interesting to see how long it lasts...

What fill is the best?

I used 20% for PLA & ABS on my printers. I can't say what is best for your printer though...

Works well thank you

I really wish the U.S. used metric and thus metric screws. Everyone else on here uses them and I much prefer the metric screw convention to our stupid English one.

Its funny to hear it called 'English'. I've only ever heard it called 'Imperial' in the UK.

Does no one supply Metric nuts and bolts in the US?

Either way the SCAD file is easy enough to change to suit whatever size nuts and bolts you have as long as you can measure them in mm.


No, online suppliers do but I can't just go down the street and get them at the local hardware store.

And Alright, I'll have to learn open scad but that doesn't sound too bad.

How do the keys stay in? A Swiss army knife has spring tension, but wouldn't this just be passive tension of the screws making it loosen up with time?

It works well with nylock lock nuts or plain nuts with some thread lock.

That said I've taken mine apart a few times so it is just passive tension holding it together now. It is in daily use and only needs tightening once in a while.

I think plain spring washers with lock nuts/thread lock would be worth trying. Also a little silicone grease wouldn't go amiss as the washers have worn into some of my keys.

As for learning scad, I think you can get away with just changing a few values in swiss_army_keyring_cutout.scad.

The variables are pretty self explanatory:

screwHoleSize = 4;
screwHeadSize = 6;

They set the screw hole diameter and screw head diameter respectively. The depth is calculated automatically as half the thickness of the body.

For the nut hole, you need to find all 3 instances of nut(5.5,4); and change them to suit. If I remember rightly the values are the distance between the peaks and flats. See 's' and 'e' on this diagram: http://www.graphskill.co.uk/hexnuts.html

Sep 8, 2014 - Modified Sep 8, 2014

I know I can just cut it off post-print. But how would I remove the keyring piece in the scad file? Don't plan to ever attach a keyring to this (the whole point for me is to move away from keyring in pocket completely)

EDIT: Nevermind, found it myself. Just clip out the last IF section. Then create once with renderNutHoles as 1, and again as 0. Print both results and done. (pretty sure)

Yup - thats the one - it is wrapped in the if statement to not add the clip when generating the other side of the keyring.

Nice touch on the design.

Thanks. IMHO It really needed it as getting keys out one handed was a real pain.

Woah! Those things are huge!

At first I though I'd accidentally scaled it up in slic3r.

Need to rework the scad files and get the dimension back to normal!

New file uploaded. This time I've printed it and it works.

Jun 7, 2013 - Modified Mar 4, 2015
MarkBenson - in reply to MarkBenson

Looks like the Minkowski sum function in scad is adding the diameter of the sphere I was using to round the corners out to the overall size of the model. Well you live and learn. Will fix, test and re-upload.

Printed this and it works fine, except that I cannot find nuts to fit the hex slots. I would also suggest beefing up the loop, as it looks like an accidental twist would break it off.

The nuts should be M3 sized. I will check dimensions and try printing one soon.

I found on the original that when fitted to a key ring, the loop was in the way of one key, making it impossible to open that key. I think it needs moving as well as beefing up. Will look at that soon as well...

It'd be cool if this could be a customizer based thing, that way people can choose the diameter of the nuts/screws based on what they have available. I have not yet made a customizable thing, but my understanding is that it's just minimal modifications to a SCAD file.

The openscad file is mostly parametric. I haven't tested it extensively so it might not all work correctly.
The first section of the file has all the variables for the various sizes. The only thing that isn't setup as a variable is the nut size, but that can easily be changed further down in the file.

Yeah, I did take a look at it, and it does make OpenSCAD hang for quite a bit when opened, so I suspect it could have issues in Customizer... however I think it could be simplified without losing anything.
Hopefully I have some time to give it a spin myself, but I am always overextended.