I've had this issue with these small grub screws that tighten the collar to the main shaft. They are very soft metal and can be wallowed out very easily and then can't be removed. I have a few of these grub screws, not just in the collar but in other parts on other helis that once they get wallowed out, I have yet to figure out how to get them out. I presume there is a tap or ease out of some kind that you could use to remove them but not sure as to what size to use or where to get one that small.
Any ideas would be appreciated. Have a couple collars and a couple tail parts that I've had the same problem with that if I could get them out I would have some good parts to use.
Thanks,
Donnie

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1st Belt CP, HXT 900 servos, Ti-turnbuckles RDTS MOD, Exceed 325 CF Blades
2nd CP-CF Telebee gyro, CopterX head/ taiL DX6I
CopterX450AE 450HDX-3550, Y-G401B HH, Volcano 40A esc, MKS-DS480 Tail , MG-14's cyclic