I have recently purchased this chuck but came with no instruction. So just how tight should the piece of wood be held? I put the rubber buttons on the plate and screwed them in but one split. I probably over did the screwing in but no guidance given. Once I completed the work I had black rubber marks on the bowl rim. Advice would be appreciated.
Like anything, just tight enough to hold it, the description says "gently hold the outside of a bowl" after all you have just made it you don't want to crush it! also keep the lathe speed down and take light cuts this is just finishing your project, be careful not to harm the work you have put into it.
I just pinch up the bolts holding the rubber stops in place never go tighter than light finger tight, there is no need they are not in the line of rotation, also you want some flex left in the rubber to grip your bowl rim gently.
I recommend that you contact Sorby direct about the split rubber on email@example.com they are always helpful, but please remember everyone is working with reduced staff at the moment.
Ask any ten woodturners for an opinion on how x is achieved, you can expect at least eleven different answers.