A flange nut delivers a crafted-in washer (flange) that distributes the clamping load around a wider spot than a regular lock nut. The look does not demand a flat washer and is also the higher selection for an outsized or slotted hole. Flange lock sizing measures from the nominal thread https://autobrakeparts09630.pointblog.net/details-fiction-and-custom-bolt-69427035