Here are 3 Major CNC Bit mistakes new CNC router owners make... 1. They do not clean sawdust from the spindle during every bit change. - This allows the bit to slip in the collet while carving, causing the project to get ruined. 2. They try to get as much cutting depth as possible, by only putting a small amount of shank in the collet. - When this is fine, the collet does not have enough shank to hold on to, allowing the router bit to wobble, causing it to have too much deflection and will break