I created this wallet card key holder to allow me to place my keys directly into my slim wallet without them falling out. The wallet card is 3 mm thick overall and the shallower part is 1 mm thick. The hollow part allows for the screw head to sit flush in the wallet.
I put my 2 keys together with a Chicago screw that is M4 (4 mm diameter post) with a 4 mm length. I prevent the screw from coming unscrewed by securing it with Threadlocker Blue 242.
The card is ID-1 size, which is a fairly standard size and should fit most wallets.
The wallet in the photo is the Slim 3 from Supr (https://www.suprgood.com/collections/slim-3-wallets). I previously used the Slim 1 which works well too.
This does add slight bulk to my slim wallet, but previously my keys would occasionally just slip out of my wallet if I wasn't careful, whereas now they are very secure. The keys are still easy to remove.
I'm not a 3D printing expert, so unfortunately I can't give a lot of guidance on the printer specifics. Printing it with PLA and 20% infill seemed to work fine though!
Key_holder_4.stl | 17.7KB |