Abstract / scope
ISO 12257:2008 specifies the dimensions of metric internal six-lobe drives used in metric screws in nominal thread diameter range 3 mm to 20 mm.
ISO 12257:2008Published
Aerospace — Internal six-lobe drives — Metric series
Aéronautique et espace — Empreintes six lobes — Série métrique
A new edition is under development: ISO/DIS 12257.