DIN 933 full thread and DIN 931 partial thread, M1.6 to M24, plus the GB/T 5783 equivalents. A hexagon head takes an external socket, so it survives more torque than a same-size socket drive and can be held from any angle. Full-thread bolts run thread from under the head to the tip; partial-thread bolts keep a smooth shank where the joint is loaded in shear.Length is measured from under the head, so the head sits above the surface by its own height — 6.4 mm at M10. Watch M10, M12 and M14 if you work to ISO drawings: DIN uses 17, 19 and 22 mm across flats, ISO 4017 uses 16, 18 and 21. Where each one belongs, and the thread-length formula for partial thread, is in the DIN 933 vs DIN 931 comparison; the Chinese standard equivalent is covered in DIN 933 vs GB/T 5783.
