DIN 3905 pdf standard
Jun 06, 2019
It is Aerospace series - Six lobe recesses for bolts - Technical specification; German and English version EN 3905:2008
DIN 3905 specifices the qualification requirement for six lobe recesses defined by EN 3911 for blots.
Standards references as follow:
EN 3911 aerospace
ISO 5855-2 aerospace MJ thread