Proteus Key Holder

by ProteanMan, published

Proteus Key Holder by ProteanMan Jan 7, 2018


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Swiss Army Knife Style Key Holder
updated February 23rd 2018

All the info you need should be in this description. If you have any further questions please check the comments section.

People have been sending tips! This is great considering that creating these designs and testing/adjusting from feedback takes time and effort. If you like the Proteus Keyholder consider sending a tip through the Tip Designer button on my profile page: https://www.thingiverse.com/ProteanMan/about

This works like a swiss army knife with your keys folding into the holder. Each holder is designed to have an equal number of keys at each end. The center bolt keeps the keys from crossing onto each other. You can fit as many keys as you want on this, just have to get a long enough bolt.

Old fashioned key size. This is a requested edition and has been sized to fit a general purpose old fashioned key (see image). You will need spacers for this one - look in the files. This size is larger than the standard key size with a length of 112mm and a width of 33mm.


  • 3mm Bolts
  • 2mm Bolts
  • Large Key Ring
  • Small Key Ring

Materials Needed

  • PETG, HTPLA, or ABS are preferred. Anything stronger works too. PLA may be too weak for regular use.
  • 3x bolts
  • 3x nuts or knurls
    (If you don't know what a knurl is then look at the pictures. You can buy them in packages online. Check image for knurl dimensions needed)

Bolt Sizes
Both 3mm and 2mm bolts can be found by measuring the thickness of the keys you want to put into the key holder + 6mm.
example: 6 keys with 3 at each end (pictures). 3 keys total width is 10mm + 6mm for keyholder body insets = 16mm bolt length.

Knurl Sizes
There is a picture with the suggested dimensions of the Knurls. 3mm and 2mm knurls have varying dimensions based on manufacturer. They won't work unless you have the proper dimensions to grip the holes. Knurls can be easily put in with a large set of plyers/clamp/hammer. They need to be pushed into place so that the edges cut and grip the hole. I use these for almost everything since they are easier and more reliable than standard nuts.

Key Spacers
There are two sizes of spacers. You can use a washer if you want, but plastic spacers may be better for the keys.
Standard Key Spacers come in 1mm and 1.5mm thickness
Old Fashioned Style Key Spacers come in 1mm and 2mm thickness. You can make your own easily through www.tinkercad.com if you don't have a CAD program.

Note: I personally don't use spacers since I like how the keys grip each other and stay together in my pocket. It's all personal preference.

Print with the inside face of each part on the print bed. This should work perfectly for any printer.
Try using high infill - 75% or above when printing.

Any ideas let me know. Enjoy!

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Beautiful renders. Solidworks? Also, have you considered shoulder bolts, so that the tension is not too great? and nylon washers for low friction. I have made an uglier version of this with these parts.

Thank you.
Everything is in Fusion 360.

I have considered shoulder bolts. Most don't have them or can get them easily - or so I'm guessing because hardware stores tend to not have them this small. I didn't find much of an issue using threaded bolts with the keys. If you want to drill a larger hole for you're shoulder bolts then maybe let me know how that works. They would have to be very shallow bolts as well considering the thickness of the parts.
Share a picture of your version? You can attach it to the comments here.

Great idea and very useful in daily lifes

Thanks. Happy that you're enjoying it!

Could you link to the little Knurled nuts you use. I found a set on Amazon, but don't know if they're the right ones and also if they're the right size.

I got them off of Ebay but you can find them anywhere.

There is an image that shows the 3mm and 2mm knurls with their heights and diameters. Just go with that from the image.

Typically it's ScrewSize-x-Diameter-x-Height
In this case it would be M3x5x4


Hi, i made some spacers for abloy brand keys - is it cool that i check those spacers to be "remix" of your key holder?

Really nice design btw, i think this made into my EDC right away, one day behind already.

this really made into my EDC. And that is something really cool, as i am really, really picky about what i carry around with me all the time. Really cool design.

I saw the remix. Thanks for thinking about that. If you have any images of them in action I can add them to the main page here and in the description.

Hey, in picture 4 I fell in love with this gear keychain, can you tell me where you bought it? it just looks amazing

That is from someone else. One of the makes of the keyholder. Look under the Made (button beside Comments) link and you can contact the person there.

I wondered about that too. It looks like a pocket watch? from the back

What material did you print the items in you pictures with?

PETG. I use this material 95% of the time. It doesn't make as smooth of a print as ABS but it was just as strong and doesn't warp when printing. Depends what you're going for too - when I print art and sculptures I use ABS. Utility things I use PETG.

Other people use PLA as well, but that has a lower breaking point under stress.

Any chance of a M3 No Ring version? I printed a M3, Nut, Large Ring version for myself, 10 keys, M3x20 screws - works great! My boss saw it, really liked the design and immediately asked if I would print him one without a key ring, he just wants to be able to pocket it without extra bits getting in the way.

Ok I put two new _Top_NoRing files in the list.

Let me know if they are what you were thinking.

Looks great, exactly what I envisioned. Printing a set now. I really appreciate the effort!

You got it bud. I'll post that either tonight or tomorrow. Appreciate the feedback.

Is it possible to use smaller keys, like for padlocks with this design?

It's definitely possible. The cutouts are placed for standard key sizes, so you'd have to try it and see. Small keys will definitely fit since it's just a matter of their hook hole fitting the bolt size that you use when putting the keyholder together.

Works perfect with PLA and 6 keys :)

Very nice design. I just printed the version for M3 nuts. Holes were slightly too big for the nuts i got. I’ll try the 2mm size and see if that works.

Thank you.
How much of a size difference was it? Maybe try compensating in your slicer settings with the - Horizontal Expansion - option. In Cura it should be easy to find.

Hi Great design! Would you mind sharing the CAD file? I printed this out of ABS. The holes are slightly too big and too shallow for the heat set threaded inserts and, the holes on the bolt head side is slightly too small for the socket head 3mm machine screws I have.

Heat Set Threaded Inserts - do you mean Knurls? like the image I supplied or are they something different?

Maybe try drilling the Bolt Head holes larger? I am not going to be sharing the CAD files unfortunately. You can take the STL file and adjust that in your CAD program as well.

May I suggest a version for double blade keys such as this:
I know its kinda like a whole other thing, but it'll be cool for us in countries that for some reason stick to those stupid blades.


Great idea. Can you send me a photo of the key you are thinking about with a ruler beside it for measurement? The KeyHolder will probably need to be adjusted for size so having the exact measurements of a common key like the one in that link would be helpful.

Ok, this took me long enough :P
You'll see on that post, that we LIVE LIKE ANIMALS! Freaking medieval keys if you ask me.

NOTE: Ruler is in centimeters!

Let me know what you think hehe.
Also posting another comment in a minute with some measurements. Just posted an update to the thread!

Those are some pretty awesome looking keys. I'll draw them into my CAD program and see if there are any changes to make them fit.
That one little tab on the side of the key @6cm, you may want to file down a notch into the key holder. Another option in the meantime if you're impatient is to scale the keyholder in your Slicer program to 1.2 or larger and see if that changes anything for you? You would have to use larger bolts and nuts as well - maybe M4 or M5?

So i ended up printing it 1:1, using the 3mm, big keyring version. I used 2 washers to make the outside keys "sandwich" the old style key with the weird blades. It sorta works. I need to get better screws, i just picked up a few random, rusted ones to do a dirty test.
I had to melt some of the PLA of the screw holes to fit said screws. I will print another one, and get the correct screws to see if it works correctly.
If it doesnt, ill:
1: Model a Key for you to have one and maybe develop your own third world compatible edition.
2: Remix your design to include cutouts so these weird keys can run on.

Ill keep you posted!


Ill try to print the keyholder at scale, and see if i can make it work. Will post an update soon, with pictures to see if it makes sense for a different version of it.

TTYL mate.

Updated with a new version to fit keys like the one you showed me. I used the measurements you gave and modeled your key. Try the new version + spacers and let me know what happens.

I printed one, and I have a couple of suggestions / requests.

A version for M3 hardware would be great. It's, in my experience, a lot more readily available.

Make the hole for the key ring larger. ~4.5mm. The ring I went to use doesn't actually fit properly. It's close, but not quite.

Increase the size of the cut in, on the model with the cut in, to make it easier to pull the key out. Thanks for the neat design.

Definitely on my list.
3mm is what I thought to work better after printing too.
I like the current cutout but will add another larger cut option.

I really like your design a lot, so I started a remix. Attached a shot of the first printed prototype. Not as fancy, but with the changes I mentioned. Just setting up a second print right now with some minor changes to tolerances. M3 hardware. Larger finger cutouts. I made it rounder overall, which is just a personal preference. I totally kept your hole spacing, and overall footprint.

Updated with M3 options and Larger Key Ring option.

Nice job on all the reworks. That was super quick.

Looks great! I think you'll find the finger inset holes easier to use if you switch the position of the keys. The end of the key is meant to be in the inset hole not the beginning (where you hold the key). Look at the picture of the one I printed above.

Well... I feel silly now. lol.

I did the same thing when I first put it together.

Are any of the photos printed items or all generated?

Just added a photo of my printed version.