How to make your own Threaded insert (Helicoil)
Using a cheap drill press,
a M12 bolt,
Ø 8.5mm & Ø 10.2mm drill bits,
M10 & M12 taps.
By following the same way,
you can make any helicoil with an acceptable combination of threads.
Attachment 7074
https://youtu.be/ng7OdRUD0G8