Reply by ocwoodworker

Or are you talking about the shank? A smaller 1/4” shank is good when you have a small round-over bits. When you start to get into some beefy round-overs ( or any bit that has an overall profile bigger than 1/2” is my rule of thumb) it’s better to step up to a 1/2” collet. It has less vibration which in turn give a cleaner cut.

-- I'd like to believe Murphy's Law haunts my woodshop, because if it's Karma it would mean I had something to do with it. - K.R.