I made this to have some better control over the insertion of 3mm threaded inserts instead of using a soldering iron. I have a 40mmx3mm screw through it with a nut inset to hold it in place. The two other nuts have loctite applied and tighted together. A small washer could be placed between the threaded insert and the nut to ensure you don't push it too far in. Heating is done with a hot air gun. The threaded insert will retain enough heat after a few minutes of heating to push easily into PLA, PETG, or ABS.