Improve the thread pitch on 3D printed nuts and bolts

thingiverse

It is a system to improve the screw threads of nuts, screws, pipe joints, caps, etc. printed in ABS without taper or tapping. In some assemblies we can save the metal inserts by making the thread directly in the printed piece. 1- For small threads (M10 or less) the wall of the thread can be printed smoothly. If it is larger, print the part with the thread pitch (male or female) as accurate as possible. In the example files there is a thread pitch of 1/2 BSP ISO 218-1 used in plumbing in Spain. On the internet it is easy to find tables with the dimensions of the different standardized thread steps. 2- Take a metal screw/nut with the same thread pitch of the printed part. If we have printed an external thread, take a nut. If we have printed an inner thread, use a screw. In this case I have used recycled plumbing pieces 1/2. 3 - Put some grease on the metal thread to prevent the plastic from sticking. 4- Put some ABS solvent (acetone, butanone, Griffon PVC cleaner) repeatedly to the printed thread with a paintbrush. Repeat for a few minutes. The deeper the thread, the longer the time. The purpose is to soften the plastic enough to mold the thread. The amount of solvent applied and the waiting time is variable and given by the experience. 5- Slowly screw the metal screw/nut into the plastic piece along the length of the thread that we want to improve. Regardless of size, you should be able to tighten only with your fingers. If it is not possible, not enough solvent has been put in or sufficient time has not been waited in the previous step. 6- Let the plastic piece dry for a couple of hours. 7- Unscrew the screw/nut and clean the grease traps. At the end of the process we will have a fairly precise thread and that screws perfectly without resistance.