This model is great for testing your printer and print settings! Even better, you'll get a feel for what size nuts and bolts will work well when designing functional things with CAD - it often takes some trial and error. Feel free to scale the nuts up or down until you find a good fit.

This being said, the nuts and bolt in my models are all nominal values from M3 to M10. Because of printer tolerances, this means corresponding nuts and bolts likely won't fit together without some playing around. For example, an M10 nut might fit well onto an M9 bolt, or you might find that something in between 9 and 10mm works best.

Enjoy and feel free to let me know how it's working!