I have one model down the X1SP 500w brushless with timing belt which converted to CNC and tend to use 0.25mm DOC with flycutter at 900mm/m without problem, these are mini in my case micro machines though and need to be listened to especially with geared drives if they sound unhappy or under stress they are prone to self destruct if not listened to. #As for getting new gear for it I can only think of http://www.beltingonline.com/gears-r...1611ed7i9j90o4 they are best value I have found.