I just today tested an M5x0.8 thread mill from Aliexpress. No big deal doing the Conversational, worked great in the delrin I am learning on. Used the Drill tab to locate the holes, milled the holes using a 2mm end mill (no 4.2mm stub drills yet), then the thread milling.
https://huhaocnctool.aliexpress.com/store/3362033 was the store I bought from. Bought 2 of M3, M4, and M6. I used the M4 one todo the M5 threading.
Aluminum next, then steel. Going down the list of skills to practice.
Gerrit