Quote Originally Posted by Jonathan View Post
Bearing in mind how ER collets barely hold cutters tight enough at the best of times using a bigger collet wont help.
Use decent quality collets and chuck, make sure they're clean and located in the nut properly, and you shouldn't have any problems. Only time I've had problems is when I've tried to cut corners while swapping tools, and got a bit dirt in or not located them in the nut properly.