Tap It
After printing the Nikon bevel with the countersunk holes I decided to do further test tapping bolt holes into the plastic. Here are my observations far.
Tapping M3 M4 threads into Marine board (black in the photo) works however the initial pressure is very sensitive in that the threads near the entry side may not be formed properly. This problem increases as the diameter goes down.
The threads at the holes exit are better. So tap from the undesired side.
Tapping 3D printed PETG with a 0.8mm wall thickness ends in disappointment. Plastic shreds.
Increasing the wall thickness to 2mm, which increasing printing time, will allow a thread to be cut.
It helps a bit to clamp a pre-tapped AL plate to the surface to help control the tapping pressure.
I suspect tapping M5 holes would work better,
In general is it worth tapping a 3D printed part?
If you tap from the far side and it fails you can drill it out and use a longer bolt and nut. Given this effort, why not do this to begin with?
Additionally. A bolt going all the way through with a nut means the printed part is in compression all of the time, which means much less likely, too fail.
