Ultralight Utility Knife

Overview

Note: requires 6x 6mm M2 bolts and nuts.

This is simple design that takes a single utility blade and gives it a handle and sheath to turn it into a functional knife. Almost the entire length of the blade is exposed in this design, so there's a fair bit of cutting area to work with compared to a normal utility knife which only exposes about half. One tradeoff of this extra blade length is that this design isn't quite as resistant to twisting forces as some utility knives, but it still ends up being very useful for general cutting purposes. It's also super lightweight: only 21 g (0.75 oz.) on my scale, making it super easy to bring this along on all your camping and backpacking expeditions and explorations.

I designed the blade handle interface so that the primary cutting forces will be directed from the blade into the assembly screws, so there shouldn't be any danger of the blade suddenly slipping free during use. I haven't broken any of my prototypes, even after putting some serious force through the blade while whittling some wood, so I'm confident that this will hold up to general cutting and slicing pretty well. If you really tried and started twisting and prying with a lot of force, you'd probably be able to break something (either the blade or the handle) though, so be careful and use common sense whenever using sharp tools like this one. 

The sheath friction fits over the blade and should be tight enough that there's no risk of it falling off accidentally. You can adjust the amount of friction by tightening/loosening the assembly screws. There are plenty of holes which you can use to can clip this knife onto something with a carabiner or similar but give it a good shake to make sure everything is secure.

Printing

Parts should automatically be oriented correctly when you load them into your slicer. No supports are required (holes are self-bridging.) To help keep the mating surfaces flat/smooth I recommend turning on ironing, but this is optional. For strength, I would suggest using at least 3-4 perimeters, and maybe 20-30% of your favorite infill. I used PETG, but PLA or ABS should also work well.

Hardware

You'll need 6x M2 nuts and 6x 6mm M2 button head or socket head cap screws, as well as a utility blade. I used heavy duty Stanley blades (0.6 mm thick), but most other standard size utility blades should work. If they have different dimensions, then they may not fit quite as intended and some adjustment might be necessary. Let me know if you have any problems.

Assembly

Assembly is very straightforward. Press the nuts into the back of the Handle A and Sheath A components. Lay the blade into the recess on Handle A, pressing it into place and secure Handle B on top with screws, clamping the blade into position. Snap Sheath A and Sheath B together and secure with screws, adjusting tension as necessary to achieve the required friction fit with the blade.