Tighten your intuition: a deeper, beefier thread should bite harder and hold more. It doesn’t. Past a point, cutting threads deeper makes a bolt weaker, and most of those threads barely feel the load at all. A bolt almost never fails on its outer diameter. It snaps at the core, across the minor diameter at the root of the thread. That cross section, the tensile stress area, is what actually carries tension. A thread is a helical notch, and every bit of depth you add is material removed from exactly where the bolt is strongest. Deepen the thread and you shrink the very load-bearing core you were trying to reinforce. Then there’s the root itself. A sharp, deep thread valley is a textbook stress concentrator. Static strength shrugs it off, but under cyclic load it’s brutal: cracks nucleate at the root and fatigue life collapses. This is why rolled threads, formed under pressure with a generous root radius and locked-in compressive stress, outlast cut threads that look identical to the e...