I have 1 case slipjoint knife, and i was playing with it while watching tv. I open and closed it 100 times. Then i looked at it and noticed a brass burr when the brass and steel is sandwiched together on the inside. On the outside of the knife where you see the steel and brass sandwich you can feel another slight burr with your finger. Does this stop over time with opening and closings as it wears in, or is this how it is for life with slip joints. Thanks for the help guys.