To clean leed screw, you can use a toothpick or brass pin to get in the grooves, it depends on the type of crud that you have. If it is just dried grease you can soak it in mineral spirits or oil and wait a few days as this makes removal easier. A dremel tool works wonders a plastic wire wheel or other attachments works wonders. I polish the carriage rod in a drill motor and clean out the hole in the carriage where it goes. A Q-tip in the dremel and metal polish works well in areas where crud has built up. Steve