I also do this- just in case
Did this today myself as I always do, and the MCB was off, the machine isolator was off, the contactor for the motor was de-energised and I had tested that all was dead, but, before I touched the bare copper I toughed it to what appeared to be a reasonable earth point on the machine!
Habit I suppose!
Please pass on my regards to those concerned.
One comment that may not be popular is, I was working on a site about 20 years ago NGB were the main fixed installation contractor, I was installing CNC machinery at the time.
They had 2 guys up in a cherry picker pulling armoured cable into a bus bar tap off, bus bars were live as they were supplying the production line, everyone know this, however, the other end of the cable was not connected thus no earth path.
The issue was that the other end WAS connected the armour WAS earthed, and, it shorted across 2 phases in the tap off box, it shut down the CPD for the bus bar, thus most of the production hall. Also it blew the cherry picker electronics so the basket had to be lowered by the hand pump. The guy who had his "head" in the box looked like a cartoon character, not funny though, he was black & his hair was standing on end. I was about 20 feet from the base of the cherry picker at the time, the bang was SO loud.
The guys were OK, but the worst affected never returned to work so I was told. He just lost his "bottle".
Such incidents have a profound affect on people, beyond the physical, which hopefully this poor soul will eventually recover from. The psychological affects can be insurmountable.
This is a terrible situation which hopefully is extremely rare and will become even more so.