I printed the nuts with a 0.4 at 0.2 layer height 3 walls and 20% gyroid infill. I printed the bolt at .2 layer height and 100% infill (my kids very quickly broke the one I did at 3 walls and 20%), all parts feel very strong.

The threads were a little crunchy going together the first time, but with a little patience, and working back and forth, it'll clearance itself.

With my setting it was ~16 hours printing on my Elegoo Neptune 3 Pro, and ~400g of filament.