Pro-Tip: WD-40 isn't a very durable lubricant or a very useful penetrant oil. It was designed for aerospace purposes but DIY users cargo-culted it and it became a product.<p>For lubrication, use a more appropriate lubricant like lithium or graphite grease, motor oil, cutting oil, or dry lubricant in dusty environments.<p>For a penetrant oil, 50-50 (by volume) acetone & ATF is one of the best for rusty ferric materials. (And, in general, you should be using an anti-seize compound orthreadlocker, and/or surface coatings to prevent rust.)