They are many metric bolt models out here, but not much imperial ones, so here's some!
This is a kit of 3D printable bolts and nuts. I made sure that the fit was good between the bolt and the nut, but I also made sure you could use a 3d printed one on a metal one.
I'll add more length, sizes and nut types over time, but let me know in the comments if there is one you'd like me to add to the presets and I'll prioritize it.
I'll include the f3d files in case you want to customize it, but appologies in advance, for some reason, I decided to use millimeters instead of inches.
UPDATES:
2024-05-18: Some files were mixed up. I deleted, re-uploaded and reorganized them.