I have a 1950's Sheldon lathe mostly in good working order. I'm, having a problem with the cross feed when using the clutch. It stops and I can manually get it going again. When I hand crank it I can feel tight spots or obstructions in the mechanism. I don't know how to take it apart to clean it's inner workings. Any suggestions? I have a Sheldon manual but it doesn't have an exploded view of the inner workings.