Made a simple nut and bolt. It is a 1/2"-13 thread. Has a 0.17mm tolerance added to the threads so it should print fine on most FDM and still thread together. Prints perfect on my E3 Pro and screws together with ease right after printing. Usually takes 1-2 full threading's to remove any imperfections and get it to move smoothly.

Bolt is just under 2 inches long. Has about 1.5" of useable threads. I made mine in ABS (10% infill), took just over an hour.