Usual preface, I’m with PreciseBits so while I try to only post general information take everything I say with the understanding that I have a bias.
As others have said. Don’t cheap out on the collet. It can be even worse than usual when you are dealing with these larger mass, large head tools. Especially if they are sticking out a decent length. You can beat up the spindle bearings if you have too much runout.
As Will said I don’t have a horse in this race as we don’t currently carry metric collets. Probably okay with Maritool. But if you want good ones with a measured spec for the collet you get, they would be. Regofix, Pioneer, Haimer, maybe Techniks UP grade (don’t know after they were bought out).
Won’t belabor the point more… again… But if you want more info on this let me know or see:
Poor nuts or use can also cause issues that are exacerbated by large mass, or long tooling. Again if you want more info let me know or: