I wanted to make this bolt look a little bit more "realistic", so I took a bolt and a nut from the Fusion 360 McMasters-Carr parts library and modified it.

I printed the nut and the head of the bolt without brim. Since the the bolt is quite long it is better to print it with a brim.

Update: I added a version of the bolt with a smaller inner hole. Should have increased strenght when you scale it up.