Butterfly No-Knife - A Bladeless Balisong Fidget Toy

A butterfly knife/balisong without a blade? A butterfly… nothing? A Butterfly No-Knife!

After seeing videos of these things, I felt I had to try one, and thought it would be quite easy to CAD up. A few prototypes later, this is the result. Only requires two M3x10mm Socket Head Cap Screws (SHCS) to assemble, you probably have a few in the spares kit of your 3D-printer (at least if it's a Prusa).

Print Settings

I recommend printing the bushings and washers out of PLA, ASA or some other material with little to no stringing. For the handles and hinge mostly anything goes, I personally printed mine in PETG for the durability.

Everything is designed for a 0.4mm nozzle and a layer height of 0.2mm. I'd recommend at least 60% infill in the handles for a more satisfying feel. The tolerances are quite tight to minimize play in the joints (while still allowing free movement in the intended directions), so scaling the model will probably not work very well.

Handle Decoration

The handles can be printed single colored as is, with indented decoration. If you want smooth handles without decoration, you can use the Handles MMU.3mf file and print that single colored. However, the intended use of the Handles MMU.3mf file is, of course, multi-material printing for colored decoration.

Assembly

1. Put a bushing in one of the holes of the hinge part.
2. Slide hinge part with bushing into the slot of one of the handles.
3. Slide a washer into the gap between handle and hinge. Use a thin screwdriver to push it in. When you can see it through the screw hole, pull it in the rest of the way. It should click in place (depending on filament used).
4. Turn over the handle and hinge together and repeat step 3 on the other side.
5. Put a M3x10mm socket head cap screw in the screw hole and tighten. (Don't overtighten, you might strip the hole!)
6. Loosen the screw until the handle moves freely in the hinge. If it never moves freely, check that the washers are in the correct position. Removing one (or both) of them might also be an option.
7. Repeat all the steps for the other handle.

Credit Where Credit Is Due

The concept is inspired by Heibel Knives FunChucks and OSP Flipping Styx.