Most good machinist know that WD-40 will and can gum up after several years of usage. It also will prevent rust but is not near as effective as several other "Gun Oils" on the market. I am not sure why someone would want to use it? I see some of my friends doing it, and there only reason was "My Daddy used to say, it is better than anything out there". I tell them thats a pretty poor excuse. My parents used to tell me alot of things, and when I got older I found out alot of it was right but a whole lot of it was wrong. Besides, saying "my daddy said this or that", makes you sound like Forest Gump.