I have on one of my past projects some M6 nuts that can come loose. So I have a need to adjust the nut tension every so often. I want to be able to just finger tighten the nut and don't want to go out and buy metal butterfly/wing nuts.
My simple solution to my butterfly nut needs was to 3D print a part that fits around the existing M6 nut providing the "wings" to finger tighten the nut. The printed part colour also matches nicely with the past project colour. There's a thin printed layer on the printed part to go on the bolt side of the nut to keep the butterfly nut in-place. This thin layer is only 0.2mm, so won't demand much from the bolt length.
Here is my 3D design. My design may match your needs, too.
My print is made with eSUN PETG 1.75mm Orange filament, with 0.2mm layer height and 15% infill on a Bambu X1 Carbon printer. No supports required.
I hope that you can find this print useful, too.
Remember to leave me some feedback or even a tip to keep me enthused to make more of these drawings.
For more of my models, see my main uploads site: https://makerworld.com/en/u/3687936443