Micro Foldable Box-Cutter Keychain (33x17mm)

thingiverse

This is a compact foldable keychain designed to securely hold one or two sections of 9mm blade from a classic box-cutter with snap-off blades. I required something that could safely cut open post packages and small ropes while fitting in my pocket, so I created this one using Solidworks. It took me seven prototypes before finding the perfect design. EDIT: I added a new way to insert the blade, which is significantly improved. The blade was sometimes slipping out of its socket, so I redesigned it. Now you can insert the blade from the front and behind, and it locks securely into place. Additionally, the blade is positioned on a corner, making it easier to open packages. The updated file for the interior is 6_int_better.stl. Key Features: There is a small protrusion that allows you to easily open it with one hand between your index finger and thumb. It's remarkably compact, measuring approximately 3cm x 2cm when folded. You can attach it to a keyring. The design is intended to be a snug fit, preventing accidental opening in your pocket or the blade from coming loose. If you encounter issues due to printer tolerances, try heating the sheath with a lighter (2 seconds) and gently pressing on the sides; this should tighten the fit. Printing Instructions: The initial file should suffice for most printers, but be sure to add supports underneath without inside the model (I've included a screenshot of Cura as reference). You can also attempt printing-in-place for added strength on the hinge, although it's a more challenging print. Alternatively, you can print both pieces separately in any orientation according to your printer settings. If you experience difficulties, the simplest approach is to print 4_ext flat on its side with internal supports and 5_int in the same manner but with supports only underneath. Please note that this design is optimized for a 0.4mm nozzle; I'm unsure if the tolerances are suitable for larger nozzles. If you'd like to adjust the design, I've included the Solidworks files.