I created the nut and bolt for my 2 year old Grandson. The threads are large and they work really smooth, I made them with a lot of tolerance so they spin on and off. My Grandson can put them together easily and he loves playing with them. I also made a few plates and washers. I made a wrench and screw driver to go along with the parts. He is learning how to bolt parts together.
I printed it on a Monoprice Dual head with ABS bed temp 105 Head 225. Bed material clean PEI. No support, no raft with 20% infill I also print a three outline skirt to make sure the head is running good.I have the front of the printer enclosed and I put panels on the top sides to keep the heat in for the ABS. With the PEI I get very little warping.