is there a trick to inserting them, bought the small kit for 8mm, drill bit, tap and coils, but cant seem to get them inserted, get like one or two threads in and stops!

Make sure you run the tap they give you down the hole a few times. Clean all the shavings out of the tap and hole before each try, compressed air works great but watch out for your eyes. The tap should go in smoothly when you are done. If there are any burrs in the threads of the hole the coil will hang and cause it to tighten up when installing. Make sure you are using the installation mandrel that comes with the kit and the tang goes down not up, this makes the coil shrink when tightening to make it easier to install. Hope this helps.

didnt have a mandrel, tried needle nose but tang snaped off before it got ressesd.