well it is on an electric motor that is out of a centrifuge for laboratories its all metric, the threads go into the black housing, no nut, and with an adjustable, it just wouldnt budge because you cant get any clearance. i fit a 6 mm deep 1/4 drive socket and it just fit enough for me to turn it out, and then back on, it is a german product, and a lot of these machines use oem spec so techs like me have a hard time servicing there equipment.
either way i still service them, rebuild there "unrepairable" motors, and such, just would like the correct tool to take off that bolt, i wonder if they even had that bolt made for them just so only they can remove it. maybe it looks discouraging, and im supposed to pay the 1000 to replaCE THE MOTOR instead of replacing the 15 dollar ball bearings.