1/4 20 bolt

thingiverse

This is a 20 thread bolt with 1/4 inch diameter threads, totaling .55 inches in length. I created the design using Fusion 360 software, then printed the bolt upright from PETG plastic, resting on its head. Printing it lying down might make it even stronger, but you'd need to add supports and ensure precise threading. PLA would likely print without issues, but its strength is unknown. I used this bolt on a 39-inch wingspan HOTS II model, which held up for two landings before breaking on a hard landing with two bounces.