Summary

Collection of bolts M8 Bolts and corresponding Nut.

I got good results with %50 infill and .2 mm layer height. For sturdier Bolts I recomment 100% infill.

Bolts and Nuts have 2 mm thread pitch.

Thanks for BloodyPeanuts for his/her comments. He achieved better result with following settings:
Nuts as-is with 60% infill
Bolts at 93% scaling for x and y and 100% for Z with 100% infill