Those can often crack even if done appropriately warm. I’ve generally use heated brass threaded inserts which work great. Then you have metal on metal and can be extremely strong, and when I needed an alternative I engraved a nut pocket on the back and used a clearance hole if possible.
for example for the inserts:
the tool (although regular solder iron tips work in a pinch):
I agree that what I did is the least reliable option, to be used only when nothing else is at hand and it suffices for the task.
Thanks for the link (“heated brass threaded inserts”), haven’t heard of those before. I happen to have some steel threaded wood inserts, which might work, but with the large threads, I’d probably need the heat gun.
A tap kit sounds great, but is the least cheap option if you don’t already have one.
The nut pocket is a good option (or just attaching the nut with epoxy) … but I was out of nuts too!
A clip nut can work in some cases, or maybe an expansion nut (well nut).
Yeah, It’s a smidge easier to keep them perfectly square with the tips designed for them, but have certainly just used the regular tip on my iron. For folks using these, remember you soldering iron is probably set to a much higher temperature than the thermoplastic you are inserting into, and depending on the material can really bake the plastic making it brittle. If your soldering iron doesn’t have a settable temperature just use it as quickly as possible to keep heating to a minimum